| sequence analysis of an aphid endosymbiont dna fragment containing rpob (beta-subunit of rna polymerase) and portions of rpll and rpoc. | the aphid schizaphis graminum is dependent on an association with a prokaryotic endosymbiont (buchnera aphidicola). the nucleotide (nt) sequence of a 5040 base pair (bp) dna fragment of b. aphidicola, homologous to the rpll-rpob-rpoc portion of the escherichia coli beta operon, was determined. the dna coded for the terminal 35 amino acids of rpll (large ribosomal subunit protein l7/l12), the complete rpob (beta-subunit of rna polymerase), and the first 209 amino acids of rpoc (beta'-subunit of r ... | 1992 | 1369199 |
| sequence analysis of a dna fragment from buchnera aphidicola (an endosymbiont of aphids) containing genes homologous to dnag, rpod, cyse, and secb. | the aphid, schizaphis graminum, contains a prokaryotic, obligately intracellular endosymbiont, buchnera aphidicola, which is necessary for the survival of the host. a recent study of bu. aphidicola 16s rrna has indicated that it is a member of the gamma-3 subdivision of the eubacterial class, proteobacteria, which includes escherichia coli. in order to further characterize the endosymbiont and establish its similarity to free-living eubacteria and/or organelles, we have cloned and sequenced a 45 ... | 1992 | 1398077 |
| genetic analysis of an aphid endosymbiont dna fragment homologous to the rnpa-rpmh-dnaa-dnan-gyrb region of eubacteria. | buchnera aphidicola is a gram- eubacterium with a dna g+c content of 28-30 mol%. this organism is an obligate intracellular symbiont of aphids. to determine its similarity to or difference from other eubacteria, a 4.9-kb dna fragment from b. aphidicola containing the gene homologous to escherichia coli dnaa (a gene involved in the initiation of chromosome replication) was cloned into e. coli and sequenced. the order of genes on this fragment, 60k-10k-rnpa-rpmh-dnaa-dnan-gyrb, was similar to that ... | 1992 | 1572539 |
| buchnera aphidicola (a prokaryotic endosymbiont of aphids) contains a putative 16s rrna operon unlinked to the 23s rrna-encoding gene: sequence determination, and promoter and terminator analysis. | the aphid schizaphis graminum is dependent on an association with buchnera aphidicola, an eubacterial endosymbiont located in specialized host cells. past studies have indicated that escherichia coli is the closest known relative of the endosymbiont which has many genetic attributes of free-living bacteria. in order to obtain information on the properties of highly expressed genes, we have chosen for study the single-copy rrs (gene encoding 16s rrna) of b. aphidicola. a 4.4-kb dna fragment was c ... | 1993 | 7507875 |
| characterization of a putative 23s-5s rrna operon of buchnera aphidicola (endosymbiont of aphids) unlinked to the 16s rrna-encoding gene. | buchnera aphidicola (ba) is an endosymbiont of the aphid schizaphis graminum. in order to obtain information on highly expressed genes, we have chosen to study ba genes coding for rrnas. previously, the single-copy rrs gene was cloned and sequenced [munson et al., gene 137 (1993) 171-178], and found to constitute a single transcription unit unlinked to rrl and rrf. in the present study, a 6.1-kb ba dna fragment containing rrl was cloned into escherichia coli (ec) and sequenced. based on sequence ... | 1995 | 7535281 |
| detection of buchnera, the primary prokaryotic endosymbiont of aphids, using the polymerase chain reaction. | members of the genus buchnera constitute a distinct prokaryotic lineage containing the primary endosymbionts of aphids (homoptera: aphidoidea). using synthetic oligonucleotides in conjunction with the polymerase chain reaction, we propose three approaches for the identification of members of this genus. the first is based on unique sequences within rrs (gene coding for 16s ribosomal rna). the second is based on a different and unique organization of the ribosomal rna operons of buchnera and the ... | 1994 | 7535631 |
| molecular analysis of the endosymbionts of tsetse flies: 16s rdna locus and over-expression of a chaperonin. | based on 16s rdna sequence comparison, intracellular mycetome-associated endosymbionts (p-endosymbionts) of tsetse flies (diptera: glossinidae) form a distinct lineage within the gamma-3 subdivision of proteobacteria, related to the free-living bacterium escherichia coli, midgut s-endosymbionts of various insects including tsetse flies, and to the p-endosymbiont lineage of aphids, buchnera aphidicola. gene organization and expression of several loci in intracellular microorganisms have revealed ... | 1995 | 7538012 |
| wigglesworthia gen. nov. and wigglesworthia glossinidia sp. nov., taxa consisting of the mycetocyte-associated, primary endosymbionts of tsetse flies. | the primary endosymbionts (p-endosymbionts) of tsetse flies (diptera: glossinidae) are harbored inside specialized cells (mycetocytes) in the anterior region of the gut, and these specialized cells form a white, u-shaped organelle called mycetome. the p-endosymbionts of five tsetse fly species belonging to the glossinidae have been characterized morphologically, and their 16s ribosomal dna sequences have been determined for phylogenetic analysis. these organisms were found to belong to a distinc ... | 1995 | 7547309 |
| discovery and molecular characterization of a plasmid localized in buchnera sp. bacterial endosymbiont of the aphid rhopalosiphum padi. | we have identified and completely sequenced a novel plasmid isolated from the aphid rhopalosiphum padi. evidence which suggests that the plasmid occurs localized within the bacterial endosymbionts is presented. the plasmid contains the four genes that constitute the entire leucine operon. this fact makes it really unique since most plasmids are dispensable and lack genes that encode essential anabolic functions. four more phloem-feeding aphid species also seem to contain homologous plasmids. alt ... | 1995 | 7608990 |
| genetics of the tryptophan biosynthetic pathway of the prokaryotic endosymbiont (buchnera) of the aphid schlechtendalia chinensis. | two dna fragments (3941 and 7152 base pairs) from the procaryotic endosymbiont (buchnera) of the aphid schlechtendalia chinensis were cloned and sequenced. the smaller fragment contained trpeg and the larger fragment contained trpdc(f)ba, genes coding for enzymes of the tryptophan biosynthetic pathway which convert chorismate to tryptophan. both of these gene clusters were present as one copy on the endosymbiont chromosome and probably constitute two transcription units. the deduced amino acid s ... | 1995 | 7742976 |
| aspects of energy-yielding metabolism in the aphid, schizaphis graminum, and its endosymbiont: detection of gene fragments potentially coding for the atp synthase beta-subunit and glyceraldehyde-3-phosphate dehydrogenase. | specialized cells within the aphid, schizaphis graminum, contain intracellular, vesicle-enclosed eubacterial endosymbionts (buchnera aphidicola). using oligonucleotide probes derived from conserved sequences of the atp synthase beta-subunit and glyceraldehyde-3-phosphate dehydrogenase, and the polymerase chain reaction (pcr), we have amplified, cloned, and sequenced three dna fragments. amino acid sequence similarity indicated that two of these fragments corresponded to endosymbiont and host gen ... | 1993 | 7763501 |
| buchnera aphidicola (aphid-endosymbiont) glyceraldehyde-3-phosphate dehydrogenase: molecular cloning and sequence analysis. | buchnera aphidicola is an endosymbiont of the aphid schizaphis graminum. a 3.9-kb b. aphidicola dna fragment was sequenced and found to contain two open reading frames (orfs). the deduced amino acid sequence of one of the orfs had an 85% identity to escherichia coli glyceraldehyde-3-phosphate dehydrogenase (gap). both of these proteins have a higher similarity to eukaryotic than to prokaryotic gaps. the second orf could not be readily identified. the sequence of the putative product indicated th ... | 1995 | 7765846 |
| aromatic amino acid biosynthesis in buchnera aphidicola (endosymbiont of aphids): cloning and sequencing of a dna fragment containing aroh-thrs-infc-rpmi-rplt. | a 4.5-kilobase dna fragment from buchnera aphidicola, the endosymbiont of the aphid schizaphis graminum, was cloned and sequenced. on the basis of homology to escherichia coli, the following genes were found in the order listed: aroh-thrs-infc-rpmi-rplt. aroh corresponds to the e. coli tryptophan-inhibited 3-deoxy-d-arabino-heptulosonate-7-phosphate (dahp) synthase. evidence was presented indicating that this is the sole gene for dahp synthase in the b. aphidicola genome. this enzyme initiates t ... | 1995 | 7766160 |
| amplification of trpeg: adaptation of buchnera aphidicola to an endosymbiotic association with aphids. | survival of aphids is dependent on an association with a prokaryotic endosymbiont (buchnera aphidicola) found in specialized cells within the aphid body cavity. recent nutritional and physiological studies have indicated that one of the functions of the endosymbionts is the synthesis of tryptophan [douglas, a. e. & prosser, w. a. (1992) j. insect physiol. 38, 565-568]. b. aphidicola resembles in many of its properties free-living prokaryotes. an adaptation to an endosymbiosis involving the overp ... | 1994 | 8170994 |
| molecular cloning and nucleotide sequence of a putative trpdc(f)ba operon in buchnera aphidicola (endosymbiont of the aphid schizaphis graminum). | a 8,392-nucleotide-long dna fragment from buchnera aphidicola (endosymbiont of the aphid schizaphis graminum) contained five genes of the tryptophan biosynthetic pathway [trpdc(f)ba] which code for enzymes converting anthranilate to tryptophan. these genes are probably arranged as a single transcription unit. downstream of the trp genes were orf-v, orf-vi, and p14, three open reading frames which in escherichia coli are also found downstream of the trp operon. upstream of the b. aphidicola trp g ... | 1993 | 8407819 |
| genetics, physiology, and evolutionary relationships of the genus buchnera: intracellular symbionts of aphids. | evolutionary studies suggest that 200-250 million years ago an aphid ancestor was infected with a free-living eubacterium. the latter became established within aphid cells. host and endosymbiont (genus buchnera) became interdependent and unable to survive without each other. the growth of buchnera became integrated with that of the aphids, which acquired the endosymbionts from their mothers before birth. speciation of host lineages was paralleled by divergence of associated endosymbiont lineages ... | 1995 | 8561471 |
| ribosomal protein s1 (rpsa) of buchnera aphidicola, the endosymbiont of aphids: characterization of the gene and detection of the product. | buchnera aphidicola is a prokaryotic endosymbiont found in specialized cells of the aphid schizaphis graminum. many of the previously cloned b. aphidicola genes are preceded by a poor ribosome-binding site. ribosomal protein s1 (rpsa) allows the translation of messenger rnas that lack or have a poor ribosome binding site. we have cloned and sequenced a 4.5-kilobase (kb) b. aphidicola dna fragment containing four open reading frames corresponding to aroa-rpsa-himd-tpia. the deduced amino acid seq ... | 1996 | 8574133 |
| the endosymbiont (buchnera sp.) of the aphid diuraphis noxia contains plasmids consisting of trpeg and tandem repeats of trpeg pseudogenes. | most aphids are dependent for their survival on prokaryotic endosymbionts assigned to the genus buchnera. among the functions of buchnera species is the synthesis of tryptophan, which is required by the aphid host. in buchnera species from the aphid diuraphis noxia, the genes for anthranilate synthase (trpeg) were found on a plasmid which consisted of seven tandem repeats of a 3.2-kb unit and one 2.6-kb unit which differed in containing a 0.6-kb deletion. one of the 3.2-kb units contained open r ... | 1996 | 8593038 |
| accelerated evolution and muller's rachet in endosymbiotic bacteria. | many bacteria live only within animal cells and infect hosts through cytoplasmic inheritance. these endosymbiotic lineages show distinctive population structure, with small population size and effectively no recombination. as a result, endosymbionts are expected to accumulate mildly deleterious mutations. if these constitute a substantial proportion of new mutations, endosymbionts will show (i) faster sequence evolution and (ii) a possible shift in base composition reflecting mutational bias. an ... | 1996 | 8610134 |
| molecular characterization of cyclic and obligate parthenogens in the aphid rhopalosiphum padi (l.). | holocyclic clones of the aphid rhopalosiphum padi (l.) reproduce by cyclic parthenogenesis, whereas anholocyclic individuals are obligate parthenogens. mitochondrial dna and (mtdna) and random amplified polymorphic dna markers in r. padi as well as plasmid dna markers of its bacterial endosymbiont, buchnera aphidicola, were examined to determine the extent of genetic divergence between clones with these differing breeding systems. these analyses revealed that cyclically parthenogenetic lineages ... | 1996 | 8637928 |
| the tryptophan biosynthetic pathway of aphid endosymbionts (buchnera): genetics and evolution of plasmid-associated anthranilate synthase (trpeg) within the aphididae. | the bacterial endosymbionts (buchnera) from the aphids rhopalosiphum padi, r. maidis, schizaphis graminum, and acyrthosiphon pisum contain the genes for anthranilate synthase (trpeg) on plasmids made up of one or more 3.6-kb units. anthranilate synthase is the first as well as the rate-limiting enzyme in the tryptophan biosynthetic pathway. the amplification of trpeg on plasmids may result in an increase of enzyme protein and overproduction of this essential amino acid, which is required by the ... | 1996 | 8642610 |
| evolution of dnaq, the gene encoding the editing 3' to 5' exonuclease subunit of dna polymerase iii holoenzyme in gram-negative bacteria. | the nucleotide sequences of the dnaq genes from salmonella typhimurium and buchnera aphidicola, encoding the epsilon-subunit of the dna polymerase iii holoenzyme, have been determined. the salmonella typhimurium dnaq protein consists of 243 amino acid residues with a calculated molecular weight of 27224. the buchnera aphidicola dnaq protein contains 233 amino acid residues with a calculated molecular weight of 27170. a multiple sequence alignment of the amino acid sequences of the dnaq proteins ... | 1997 | 9000520 |
| expression and control of an operon from an intracellular symbiont which is homologous to the groe operon. | members of the genus buchnera are intracellular symbionts harbored by the aphid bacteriocyte which selectively synthesize symbionin, a homolog of the escherichia coli groel protein, in vivo. symbionin and syms, a groes homolog, are encoded in the symsl operon. northern blotting and primer extension analyses revealed that the symsl operon invariably gives rise to a bicistronic mrna under the control of a heat shock promoter, though the amount of the symsl mrna in the isolated symbiont did not inc ... | 1997 | 9079916 |
| structure of the dnaa region of the endosymbiont, buchnera aphidicola, of aphid schizaphis graminum. | buchnera aphidicola is an intracellular prokaryote (endosymbiont) that lives in the body cavity of the aphid. phylogenetic studies indicated that it is closely related to escherichia coli and members of enterobacteria. the gene order of the region containing the dnaa gene is well conserved in many bacteria. seven genes of the endosymbiont of the aphid schizaphis graminum, gyrb, dnan, dnaa, rpmh, rnpa, yidd, and 60k. were found to be homologous in sequence and relative location to those of e. col ... | 1996 | 9097044 |
| the (f1f0) atp synthase of buchnera aphidicola (endosymbiont of aphids): genetic analysis of the putative atp operon. | buchnera aphidicola is an intracellular, non-cultivable prokaryotic symbiont of the aphid schizaphis graminum. a 6.8-kilobase fragment from b. aphidicola was cloned and sequenced and was found to contain genes encoding for proteins of the atp synthase. the order of the genes, atpbefhagdc, is identical to that found inescherichia coli and many other prokaryotes. this genetic organization is different from that observed in organelles such as mitochondria and chloroplasts, in which the genes are pa ... | 1997 | 9216881 |
| buchnera aphidicola (endosymbiont of aphids) contains nuoc(d) genes that encode subunits of nadh dehydrogenase. | a two-kilobase dna fragment from buchnera aphidicola, the endosymbiont of aphids, was cloned and sequenced. one open reading frame was detected, coding for a putative protein of 600 amino acids. the n-terminal portion of this protein corresponded to nuoc, while the c-terminal portion corresponded to nuod. these proteins are constituents of the membrane-associated nadh dehydrogenase. our results suggest that these two proteins are fused in buchnera aphidicola, a result consistent with their previ ... | 1997 | 9216887 |
| putative evolutionary origin of plasmids carrying the genes involved in leucine biosynthesis in buchnera aphidicola (endosymbiont of aphids). | an 8.5-kb plasmid encoding genes (leuabcd) involved in leucine biosynthesis and a small plasmid of 1.74 kb of yet unknown function were found in the intracellular symbiont, buchnera aphidicola, of two divergent aphid species, thelaxes suberi and tetraneura caerulescens, respectively. the leuabcd-carrying plasmid (pbts1) was amplified from total aphid dna by inverse long pcr, using outwardly oriented oligonucleotide primers specific to leua. the resulting 8.2-kb pcr fragment as well as the 1.74-k ... | 1997 | 9244264 |
| structure and expression of the dnakj operon of buchnera, an intracellular symbiotic bacteria of aphid. | buchnera sp., an intracellular symbiont of the pea aphid (acyrthosiphon pisum harris), is a close phylogenetical relative of escherichia coli, and synthesizes a large amount of symbionin, a groel homolog. the other heat shock protein homologs, which are not expressed as much as symbionin, have not been studied yet. in this study, we cloned the dnak and dnaj genes of buchnera, and revealed that its dnak and dnaj are structurally very similar to those of e. coli. amino acid residues and motifs pro ... | 1997 | 9276669 |
| evolution of the tryptophan biosynthetic pathway in buchnera (aphid endosymbionts): studies of plasmid-associated trpeg within the genus uroleucon. | aphids obtain tryptophan from prokaryotic endosymbionts assigned to the genus buchnera. the rate-limiting enzyme in tryptophan biosynthes, anthranilate synthase, is encoded by the genes trpe and trpg. in buchnera within the family aphididae, trpeg is plasmid-borne, apparently as an adaptation to overproduce tryptophan for hosts. to explore the evolution of these plasmids, sequences for trpeg, the upstream region containing the plasmid origin of replication, and chromosomal trpb were obtained for ... | 1997 | 9299222 |
| the n-terminal region of the luteovirus readthrough domain determines virus binding to buchnera groel and is essential for virus persistence in the aphid. | luteoviruses and the luteovirus-like pea enation mosaic virus (pemv; genus enamovirus) are transmitted by aphids in a circulative, nonreplicative manner. acquired virus particles persist for several weeks in the aphid hemolymph, in which a groel homolog, produced by the primary endosymbiont of the aphid, is abundantly present. six subgroup ii luteoviruses and pemv displayed a specific but differential affinity for escherichia coli groel and groel homologs isolated from the endosymbiotic bacteria ... | 1997 | 9311800 |
| potato leafroll virus binds to the equatorial domain of the aphid endosymbiotic groel homolog. | a groel homolog with a molecular mass of 60 kda, produced by the primary endosymbiotic bacterium (a buchnera sp.) of myzus persicae and released into the hemolymph, has previously been shown to be a key protein in the transmission of potato leafroll virus (plrv). like other luteoviruses and pea enation mosaic virus, plrv readily binds to extracellular buchnera groel, and in vivo interference in this interaction coincides with reduced capsid integrity and loss of infectivity. to gain more knowled ... | 1998 | 9420234 |
| characterization of ftsz, the cell division gene of buchnera aphidicola (endosymbiont of aphids) and detection of the product. | buchnera aphidicola, the endosymbiont of the aphid schizaphis graminum, contains the gene ftsz, which codes for a protein involved in the initiation of septum formation during cell division. with immunological techniques, this protein has been detected in cell-free extracts of the endosymbiont. nucleotide sequence determination of a 6.4-kilobase b. aphidicola dna fragment has indicated that, as in e. coli, ftsz is adjacent to genes coding for other cell division proteins as well as genes involve ... | 1998 | 9425245 |
| endosymbionts (buchnera) from the aphids schizaphis graminum and diuraphis noxia have different copy numbers of the plasmid containing the leucine biosynthetic genes. | the prokaryotic endosymbiont (buchnera) of the aphid schizaphis graminum contains 24 copies of a plasmid that has genes encoding enzymes of the leucine biosynthetic pathway while the endosymbiont of the related aphid diuraphis noxia has only one copy of this plasmid. these results, in conjunction with similar results for the trpeg-containing plasmids, suggest that d. noxia has a reduced demand for endosymbiont-derived essential amino acids. | 1998 | 9504992 |
| sequence analysis of a 34.7-kb dna segment from the genome of buchnera aphidicola (endosymbiont of aphids) containing groel, dnaa, the atp operon, gida, and rho. | buchnera aphidicola is a prokaryotic endosymbiont of the aphid schizaphis graminum. from past and present nucleotide sequence analyses of the b. aphidicola genome, we have assembled a 34. 7-kilobase (kb) dna segment. this segment contains genes coding for 32 open reading frames (orfs), which corresponded to 89.9% of the dna. all of these orfs could be identified with homologous regions of the escherichia coli genome. the order of the genes with established functions was groels-trme-rnpa-rpmh-dna ... | 1998 | 9516544 |
| differential display of mrnas related to amino acid metabolism in the endosymbiotic system of aphids. | bacteriocytes harbouring buchnera endosymbionts were isolated from young and old aphids, acyrthosiphon pisum, and their mrna populations were examined by the differential cdna display and quantitative reverse transcriptase-polymerase chain reaction (rt-pcr) technique. it was suggested that several gene products are produced when the symbiotic system is well organized in the young insect, whereas others are produced after the system becomes degenerate in old aphids. among the gene products that w ... | 1997 | 9569646 |
| evolutionary rates for tuf genes in endosymbionts of aphids. | the gene encoding elongation factor tu (tuf) in aphid endosymbionts (genus buchnera) evolves at rates of 1.3 x 10(-10) to 2.5 x 10(-10) nonsynonymous substitutions and 3.9 x 10(-9) to 8.0 x 10(-9) synonymous substitutions per position per year. these rates, which are at present among the most reliable substitution rates for protein-coding genes of bacteria, have been obtained by calibrating the nodes in the phylogenetic tree produced from the buchnera ef-tu sequences using divergence times for t ... | 1998 | 9580987 |
| the endosymbiont (buchnera) of the aphid diuraphis noxia contains all the genes of the tryptophan biosynthetic pathway. | previously it has been shown that the prokaryotic endosymbiont (buchnera) of the aphid diuraphis noxia contains a plasmid consisting of one copy of the gene for anthranilate synthase (trpeg) and seven trpeg pseudogenes. in the present communication we show that this endosymbiont contains the remaining genes of the tryptophan biosynthetic pathway [trpdc(f)ba] which appear to be functional in that they code for the complete enzyme proteins and are not pseudogenes. as in the case of buchnera from o ... | 1998 | 9625791 |
| molecular characterization of the principal symbiotic bacteria of the weevil sitophilus oryzae: a peculiar g + c content of an endocytobiotic dna. | the principal intracellular symbiotic bacteria of the cereal weevil sitophilus oryzae were characterized using the sequence of the 16s rdna gene (rrs gene) and g + c content analysis. polymerase chain reaction amplification with universal eubacterial primers of the rrs gene showed a single expected sequence of 1,501 bp. comparison of this sequence with the available database sequences placed the intracellular bacteria of s. oryzae as members of the enterobacteriaceae family, closely related to t ... | 1998 | 9664696 |
| sequence analysis of a dna fragment from buchnera aphidicola (aphid endosymbiont) containing the genes dapd-htra-ilvi-ilvh-ftsl-ftsi-mure | buchnera aphidicola is a prokaryotic endosymbiont of the aphid schizaphis graminum. one of the endosymbiont's functions is the synthesis of branched-chain amino acids. a 9.7-kilobase b. aphidicola chromosomal dna fragment was cloned and sequenced and found to contain genes encoding acetohydroxy acid synthase (ilvih), the first enzyme of the parallel pathway of isoleucine and valine biosynthesis. previously we have detected ilvc and ilvd, encoding the two other enzymes of this pathway. in additio ... | 1998 | 9688822 |
| buchnera aphidicola (aphid endosymbiont) contains genes encoding enzymes of histidine biosynthesis. | buchnera aphidicola is an endosymbiont of aphids. one of its functions appears to be the synthesis of essential amino acids for the aphid host. a 12.8-kilobase b. aphidicola dna fragment has been cloned and sequenced. it contains genes encoding all of the enzymes required for the biosynthesis of the essential amino acid histidine. the order of the genes, hisgdcbhafi, is the same as that found in escherichia coli and is consistent with their constituting a single transcription unit. the dna fragm ... | 1998 | 9767718 |
| structure and evolution of the leucine plasmids carried by the endosymbiont (buchnera aphidicola) from aphids of the family aphididae. | in all examined species of the family aphididae, the bacterial endosymbiont buchnera aphidicola carries a plasmid encoding the genes leuabcd (involved in leucine biosynthesis) along with repa1, repa2 and orf1. the gene organisation of the leucine plasmids was conserved, except in buchnera isolated from pterocomma populeum, where orf1 was located in a different position. an inverted repeat (lir1) located between repa2 and leua is found in all of the buchnera leucine plasmids examined. the predict ... | 1998 | 9812361 |
| detection of messenger rna transcribed from genes encoding enzymes of amino acid biosynthesis in buchnera aphidicola (endosymbiont of aphids). | the aphid schizaphis graminum is dependent on buchnera aphidicola, a prokaryotic endosymbiont. one of the functions of the endosymbiont is the synthesis of essential amino acids for the aphid host. previously we have found that b. aphidicola has many of the genes that encode enzymes of amino acid biosynthesis. using reverse transcriptase and the polymerase chain reaction, we have detected messenger rna corresponding to genes involved in the synthesis of tryptophan, isoleucine, valine, leucine, a ... | 1999 | 9871114 |
| plasmid-encoded anthranilate synthase (trpeg) in buchnera aphidicola from aphids of the family pemphigidae. | buchnera aphidicola is an obligate intracellular symbiont of aphids. one of its proposed functions is the synthesis of essential amino acids, nutrients required by aphids but deficient in their diet of plant phloem sap. the genetic organization of the tryptophan pathway in buchnera from proliferous aphids of the family aphididae has previously been shown to reflect a capacity to overproduce this essential amino acid (c.-y. lai, l. baumann, and p. baumann, proc. natl. acad. sci. usa 91:3819-3823, ... | 1999 | 9872768 |
| genetic characterization of plasmids containing genes encoding enzymes of leucine biosynthesis in endosymbionts (buchnera) of aphids. | the prokaryotic endosymbionts (buchnera) of aphids are known to provision their hosts with amino acids that are limiting in the aphid diet. buchnera from the aphids schizaphis graminum and diuraphis noxia have plasmids containing leuabcd, genes that encode enzymes of the leucine biosynthetic pathway, as well as genes encoding proteins probably involved in plasmid replication (repa1 and repa2) and an open reading frame (orf1) of unknown function. the newly reported plasmids closely resemble a pla ... | 1999 | 9873079 |
| physical and genetic map of the genome of buchnera, the primary endosymbiont of the pea aphid acyrthosiphon pisum. | the genome of buchnera, an endosymbiotic bacterium of the pea aphid acyrthosiphon pisum, was characterized by pulse-field gel electrophoresis (pfge) as a circular dna molecule of 657 kb. the enzymes i-ceui, cpoi, apai, smai, naei, sacii, mlui, fspi, and nrui were used to cleave the dna of buchnera into fragments of suitable size for pfge analysis. a physical map of the buchnera genome, including restriction fragments from seven of these enzymes, was constructed using double cutting, partial dige ... | 1999 | 9929382 |
| a groel homologue from endosymbiotic bacteria of the whitefly bemisia tabaci is implicated in the circulative transmission of tomato yellow leaf curl virus. | evidence for the involvement of a bemisia tabaci groel homologue in the transmission of tomato yellow leaf curl geminivirus (tylcv) is presented. a approximately 63-kda protein was identified in b. tabaci whole-body extracts using an antiserum raised against aphid buchnera groel. the groel homologue was immunolocalized to a coccoid-shaped whitefly endosymbiont. the 30 n-terminal amino acids of the whitefly groel homologue showed 80% homology with that from different aphid species and groel from ... | 1999 | 10087228 |
| intracellular bacterial symbionts of aphids possess many genomic copies per bacterium. | although buchnera, the endosymbiotic bacteria of aphids, are close relatives of escherichia coli, their genome size is only a seventh that of e. coli. in this study, we estimated the genomic copy number of buchnera by dot-blot hybridization and fluorimetry using a video-intensified microscope photon-counting system and obtained convincing evidence that each cell of these bacteria contains an average of 120 genomic copies. thus, the buchnera symbiont, with many copies of a small-sized genome, is ... | 1999 | 10229576 |
| evidence for genetic drift in endosymbionts (buchnera): analyses of protein-coding genes. | buchnera, the bacterial endosymbionts of aphids, undergo severe population bottlenecks during maternal transmission through their hosts. previous studies suggest an increased effect of drift within these strictly asexual, small populations, resulting in an increased fixation of slightly deleterious mutations. this study further explores sequence evolution in buchnera using three approaches. first, patterns of codon usage were compared across several homologous escherichia coli and buchnera loci, ... | 1999 | 10331254 |
| low genetic diversity among pea aphid (acyrthosiphon pisum) biotypes of different plant affiliation. | genetic diversity in the pea aphid acyrthosiphon pisum was investigated by a restriction fragment length polymorphism (rflp) analysis of three maternally inherited genomes (mitochondrial dna and plasmids of the symbiotic bacteria buchnera). twenty-nine parthenogenetic clones of three a. pisum biotypes, defined by their capacity to use the legume crops pea, alfalfa and red clover, respectively, were analysed, and a total of 67 restriction sites was scored. no restriction site variation in the mit ... | 1999 | 10383681 |
| phosphocarrier proteins in an intracellular symbiotic bacterium of aphids. | a groel homolog produced by buchnera, an intracellular symbiotic bacterium of aphids, is not only a molecular chaperone but also a novel phosphocarrier protein, suggesting that this protein plays a role in a signal transducing system specific to bacteria living in an intracellular environment. this prompted us to look into phosphocarrier proteins of buchnera that may be shared in common with other bacteria. as a result, no evidence was obtained for the presence of sensor kinases of the two-compo ... | 1999 | 10467175 |
| luteovirus interactions with aphid vector cellular components. | | 1999 | 10471260 |
| sequence evolution in bacterial endosymbionts having extreme base compositions. | a major limitation on ability to reconstruct bacterial evolution is the lack of dated ancestors that might be used to evaluate and calibrate molecular clocks. vertically transmitted symbionts that have cospeciated with animal hosts offer a firm basis for calibrating sequence evolution in bacteria, since fossils of the hosts can be used to date divergence events. sequences for a functionally diverse set of genes have been obtained for bacterial endosymbionts (buchnera) from two pairs of aphid hos ... | 1999 | 10555290 |
| gene size reduction in the bacterial aphid endosymbiont, buchnera. | | 1999 | 10605125 |
| acetone preservation: a practical technique for molecular analysis. | in attempts to establish a convenient and reliable method for field collection and archival preservation of insects and their endosymbiotic microorganisms for molecular analysis, acetone, ethanol, and other organic solvents were tested for dna preservability of the pea aphid acyrthosiphon pisum and its intracellular symbiotic bacterium buchnera sp. after 6 months' storage, not only the band of high-molecular-size dna but also the bands of rrna were well preserved in acetone, ethanol, 2-propanol, ... | 1999 | 10620236 |
| molecular characterization of the leucine plasmid from buchnera aphidicola, primary endosymbiont of the aphid acyrthosiphon pisum. | the complete sequence of the leucine plasmid of buchnera aphidicola from the aphid acyrthosiphon pisum (pleu-bap) is reported. its gene organization was concordant with those of other leucine plasmids of buchnera from aphids of the aphidini and macrosiphini tribes. three inverted repeats are present in pleu-bap. two of them are also present in pleu from the family aphididae: (i) sir1, located downstream the leucine operon, resembles a rho-independent terminator of transcription, and (ii) lir1, l ... | 2000 | 10688696 |
| genomic copy number of intracellular bacterial symbionts of aphids varies in response to developmental stage and morph of their host. | buchnera, endosymbiotic bacteria of aphids possess many genomic copies per cell. in this study, we estimated genomic copy number per buchnera cell from host insects at various developmental stages and of two different morphs, apterae and alatae, by fluorimetry and real-time quantitative pcr. the results indicated that the genomic copy number of buchnera increased during postembryonic development of insects to adulthood, and that it decreased during the host's ageing. in buchnera from alatae, the ... | 2000 | 10732993 |
| identifying the determinants in the equatorial domain of buchnera groel implicated in binding potato leafroll virus. | luteoviruses avoid degradation in the hemolymph of their aphid vector by interacting with a groel homolog from the aphid's primary endosymbiotic bacterium (buchnera sp.). mutational analysis of groel from the primary endosymbiont of myzus persicae (mpb groel) revealed that the amino acids mediating binding of potato leafroll virus (plrv; luteoviridae) are located within residues 9 to 19 and 427 to 457 of the n-terminal and c-terminal regions, respectively, of the discontinuous equatorial domain. ... | 2000 | 10775590 |
| prephenate dehydratase from the aphid endosymbiont (buchnera) displays changes in the regulatory domain that suggest its desensitization to inhibition by phenylalanine. | buchnera aphidicola, the prokaryotic endosymbiont of aphids, complements dietary deficiencies with the synthesis and provision of several essential amino acids. we have cloned and sequenced a region of the genome of b. aphidicola isolated from acyrthosiphon pisum which includes the two-domain aroq/phea gene. this gene encodes the bifunctional chorismate mutase-prephenate dehydratase protein, which plays a central role in l-phenylalanine biosynthesis. two changes involved in the overproduction of ... | 2000 | 10781569 |
| decoupling of genome size and sequence divergence in a symbiotic bacterium. | in contrast to genome size variation in most bacterial taxa, the small genome size of buchnera sp. was shown to be highly conserved across genetically diverse isolates (630 to 643 kb). this exceptional size conservation may reflect the inability of this obligate mutualist to acquire foreign dna and reduced selection for genetic novelty within a static intracellular environment. | 2000 | 10851009 |
| the secondary endosymbiotic bacterium of the pea aphid acyrthosiphon pisum (insecta: homoptera). | the secondary intracellular symbiotic bacterium (s-symbiont) of the pea aphid acyrthosiphon pisum was investigated to determine its prevalence among strains, its phylogenetic position, its localization in the host insect, its ultrastructure, and the cytology of the endosymbiotic system. a total of 14 aphid strains were examined, and the s-symbiont was detected in 4 japanese strains by diagnostic pcr. two types of eubacterial 16s ribosomal dna sequences were identified in disymbiotic strains; one ... | 2000 | 10877764 |
| polyamine composition and expression of genes related to polyamine biosynthesis in an aphid endosymbiont, buchnera. | polyamine composition in an aphid endosymbiotic bacterium, buchnera sp., was determined by high-performance liquid chromatographic analysis. we found that buchnera contained virtually only a single polyamine, spermidine. the spermidine content of buchnera was considerably higher in young aphids and tended to decrease with the age of the host. expression of sped and spee, whose gene products are key enzymes in the synthesis of spermidine, was analyzed by real-time quantitative reverse transcripti ... | 2000 | 10919785 |
| cospeciation between bacterial endosymbionts (buchnera) and a recent radiation of aphids (uroleucon) and pitfalls of testing for phylogenetic congruence. | previous studies of phylogenetic congruence between aphids and their symbiotic bacteria (buchnera) supported long-term vertical transmission of symbionts. however, those studies were based on distantly related aphids and would not have revealed horizontal transfer of symbionts among closely related hosts. aphid species of the genus uroleucon are closely related phylogenetically and overlap in geographic ranges, habitats, and parasitoids. to examine support for congruence of phylogenies of buchne ... | 2000 | 10937228 |
| accelerated evolution in bacterial endosymbionts of aphids. | when compared with free living bacteria, it is proposed that there are at least two endosymbiotic processes in aphids based on the a + t content as well as the increased evolutionary rate of the beta-subunit of the f-atpase complex in different endosymbiotic bacteria. the first well established process corresponds to the integration of buchnera aphidicola more than 150 million years ago. the other is postulated to correspond to new endosymbiotic processes in which the bacteria involved contain l ... | 1999 | 10943385 |
| decay of mutualistic potential in aphid endosymbionts through silencing of biosynthetic loci: buchnera of diuraphis. | buchnera, the primary bacterial endosymbiont of aphids, is known to provision essential amino acids lacking in the hosts' diet of plant sap. the recent discovery of silenced copies of genes for tryptophan biosynthesis (trpeg) in certain buchnera lineages suggests a decay in symbiotic functions in some aphid species. however, neither the distribution of pseudogenes among lineages nor the impact of this gene silencing on amino-acid availability in hosts has been assessed. in buchnera of the aphid ... | 2000 | 10983826 |
| postsymbiotic plasmid acquisition and evolution of the repa1-replicon in buchnera aphidicola. | buchnera aphidicola is an obligate, strictly vertically transmitted, bacterial symbiont of aphids. it supplies its host with essential amino acids, nutrients required by aphids but deficient in their diet of plant phloem sap. several lineages of buchnera show adaptation to their nutritional role in the form of plasmid-mediated amplification of key-genes involved in the biosynthesis of tryptophan (trpeg) and leucine (leuabcd). phylogenetic analyses of these plasmid-encoded functions have thus far ... | 2000 | 10984505 |
| genome sequence of the endocellular bacterial symbiont of aphids buchnera sp. aps. | almost all aphid species (homoptera, insecta) have 60-80 huge cells called bacteriocytes, within which are round-shaped bacteria that are designated buchnera. these bacteria are maternally transmitted to eggs and embryos through host generations, and the mutualism between the host and the bacteria is so obligate that neither can reproduce independently. buchnera is a close relative of escherichia coli, but it contains more than 100 genomic copies per cell, and its genome size is only a seventh o ... | 2000 | 10993077 |
| evolutionary genomics: is buchnera a bacterium or an organelle? | the first genome sequence of an intracellular bacterial symbiont of a eukaryotic cell has been determined. the buchnera genome shares features with the genomes of both intracellular pathogenic bacteria and eukaryotic organelles, and it may represent an intermediate between the two. | 2000 | 11114534 |
| vertical transmission of biosynthetic plasmids in aphid endosymbionts (buchnera). | this study tested for horizontal transfer of plasmids among buchnera aphidicola strains associated with ecologically and phylogenetically related aphid hosts (uroleucon species). phylogenetic congruence of buchnera plasmid (trpeg and leuabc) and chromosomal (dnan and trpb) genes supports strictly vertical long-term transmission of plasmids, which persist due to their contributions to host nutrition rather than capacity for infectious transfer. synonymous divergences indicate elevated mutation on ... | 2001 | 11133977 |
| quantifying nutrient production by the microbial symbionts in an aphid. | the symbiotic bacteria buchnera sp. provide aphids with essential amino acids, nutrients in short supply in the aphid diet of plant phloem sap. the contribution of buchnera-derived amino acids to net protein growth of the aphid aphis fabae was quantified from the protein growth of aphids reared on chemically defined diets lacking individual amino acids. the amino acid production rates varied among the nine essential amino acids over the range 8-156 pmol microg(-1)protein day(-1) (for tryptophan ... | 2001 | 11136620 |
| intraspecific variation in symbiont genomes: bottlenecks and the aphid-buchnera association. | buchnera are maternally transmitted bacterial endosymbionts that synthesize amino acids that are limiting in the diet of their aphid hosts. previous studies demonstrated accelerated sequence evolution in buchnera compared to free-living bacteria, especially for nonsynonymous substitutions. two mechanisms may explain this acceleration: relaxed purifying selection and increased fixation of slightly deleterious alleles under drift. here, we test the divergent predictions of these hypotheses for int ... | 2001 | 11156972 |
| intraspecific phylogenetic congruence among multiple symbiont genomes. | eukaryotes often form intimate endosymbioses with prokaryotic organisms. cases in which these symbionts are transmitted cytoplasmically to host progeny create the potential for co-speciation or congruent evolution among the distinct genomes of these partners. if symbionts do not move horizontally between different eukaryotic hosts, strict phylogenetic congruence of their genomes is predicted and should extend to relationships within a single host species. conversely, even rare 'host shifts' amon ... | 2000 | 11197128 |
| degenerative minimalism in the genome of a psyllid endosymbiont. | psyllids, like aphids, feed on plant phloem sap and are obligately associated with prokaryotic endosymbionts acquired through vertical transmission from an ancestral infection. we have sequenced 37 kb of dna of the genome of carsonella ruddii, the endosymbiont of psyllids, and found that it has a number of unusual properties revealing a more extreme case of degeneration than was previously reported from studies of eubacterial genomes, including that of the aphid endosymbiont buchnera aphidicola. ... | 2001 | 11222582 |
| expression of host s-adenosylmethionine decarboxylase gene and polyamine composition in aphid bacteriocytes. | differential cdna display and quantitative rt-pcr revealed that mrna of host s-adenosylmethionine decarboxylase (samdc) was abundant only in the aphid endosymbiotic system well organized in young hosts, suggesting that samdc plays some important roles in the system. samdc is a key enzyme to synthesize polyamines that are known to be involved in a large array of biological events including protein synthesis, dna stabilization, dna replication, and cell proliferation. as the first step to investig ... | 2001 | 11222959 |
| independent origins and horizontal transfer of bacterial symbionts of aphids. | many insect groups have obligate associations with primary endosymbionts: mutualistic bacteria that are maternally transmitted and derived from an ancient infection. often, the same insects are hosts to 'secondary' bacterial symbionts which are maternally transmitted but relatively labile within host lineages. to explore the dynamics of secondary symbiont associations in aphids, we characterized bacteria infecting 15 species of macrosiphine aphids using dna sequencing, diagnostic polymerase chai ... | 2001 | 11251800 |
| parallel acceleration of evolutionary rates in symbiont genes underlying host nutrition. | the overproduction of essential amino acids by buchnera aphidicola, the primary bacterial mutualist of aphids, is considered an adaptation for increased production of nutrients that are lacking in aphids' diet of plant sap. given their shared role in host nutrition, amino acid biosynthetic genes of buchnera are expected to experience parallel changes in selection that depend on host diet quality, growth rate, and population structure. this study evaluates the hypothesis of parallel selection acr ... | 2001 | 11399154 |
| mutualists and parasites: how to paint yourself into a (metabolic) corner. | eukaryotes have developed an elaborate series of interactions with bacteria that enter their bodies and/or cells. genome evolution of symbiotic and parasitic bacteria multiplying inside eukaryotic cells results in both convergent and divergent changes. the genome sequences of the symbiotic bacteria of aphids, buchnera aphidicola, and the parasitic bacteria of body louse and humans, rickettsia prowazekii, provide insights into these processes. convergent genome characteristics include reduction i ... | 2001 | 11412844 |
| molecular systematics of aphids and their primary endosymbionts. | aphids constitute a monophyletic group within the order homoptera (i.e., superfamily aphidoidea). the aphidoidea originated in the jurassic about 150 my ago from some aphidiform ancestor whose origin can be traced back to about 250 my ago. they exhibit a mutualistic association with intracellular bacteria (buchnera sp.) related to escherichia coli. buchnera is usually considered the aphids' primary endosymbiont. the association is obligate for both partners. the 16s rdna-based phylogeny of buchn ... | 2001 | 11527469 |
| regulation of aromatic amino acid biosynthesis in gamma-proteobacteria. | computational comparative techniques were applied to analysis of the aromatic amino acid regulons in gamma-proteobacteria. this resulted in characterization of the trpr and tyrr regulons in the genomes of yersinia pestis, haemophilus influenzae, vibrio cholerae and other bacteria and identification of new members of the phhr regulon in the genome of pseudomonas aeruginosa. candidate attenuators were constructed for all studied genomes, including the trpba operon of the very distantly related bac ... | 2001 | 11545272 |
| comparative genomics and evolution of genes encoding bacterial (p)ppgpp synthetases/hydrolases (the rel, rela and spot proteins). | in the gram-negative model organism escherichia coli, the effector molecule of the stringent response, (p)ppgpp, is synthesized by two different enzymes, rela and spot, whereas in the gram-positive model organism bacillus subtilis only one enzyme named rel is responsible for this activity. rel and spot also possess (p)ppgpp hydrolase activity. blast searches were used to identify orthologous genes in databases. the construction and bootstrapping of phylogenetic trees allowed classification of th ... | 2001 | 11545276 |
| the impact of host plant on the abundance and function of symbiotic bacteria in an aphid. | the black-bean aphid aphis fabae bears populations of coccoid symbiotic bacteria buchnera spp. at 2.0-3.2 x 10(7)cells mg(-1)aphid mass and rod-shaped secondary symbionts of uncertain taxonomic affiliation at 0.1-0.6 x 10(7)cells mg(-1)aphid mass. buchnera provides essential amino acids, supplementing the poor supply in the aphid diet of plant phloem sap. comparison of the performance of a. fabae containing and experimentally deprived of their bacteria showed that the bacteria caused increased l ... | 2001 | 11551991 |
| genome size reduction through multiple events of gene disintegration in buchnera aps. | the evolution of the endosymbiont buchnera during its adaptation to intracellular life involved a massive reduction in its genome. by comparing the orthologous genes of buchnera, escherichia coli and vibrio cholerae, we show that the minimal genome size of buchnera arose from multiple events of gene disintegration dispersed over the whole genome. the elimination of the genes was a continuous process that began with gene inactivation and progressed until the dna corresponding to the pseudogenes w ... | 2001 | 11672844 |
| accumulation of species-specific amino acid replacements that cause loss of particular protein functions in buchnera, an endocellular bacterial symbiont. | endosymbiotic bacteria live in animal cells and are transmitted vertically at the time of the host's reproduction. in view of their small and asexual populations with infrequent chances of recombination, these endocellular bacteria are expected to accumulate mildly deleterious mutations. previous studies showed that the dna sequences of these bacteria evolved faster than those of free-living bacteria. in this study, we compared all the orfs of buchnera, an endocellular bacterial symbiont of aphi ... | 2001 | 11675597 |
| secondary intracellular symbiotic bacteria in aphids of the genus yamatocallis (homoptera: aphididae: drepanosiphinae). | a novel secondary intracellular symbiotic bacterium from aphids of the genus yamatocallis (subfamily drepanosiphinae) was characterized by using molecular phylogenetic analysis, in situ hybridization, and diagnostic pcr detection. in the aphid tissues, this bacterium (tentatively designated ysms [yamatocallis secondary mycetocyte symbiont]) was found specifically in large cells surrounded by primary mycetocytes harboring buchnera cells. of nine drepanosiphine aphids examined, ysms was detected i ... | 2001 | 11679361 |
| the phylogenetic distribution of frataxin indicates a role in iron-sulfur cluster protein assembly. | much has been learned about the cellular pathology of friedreich's ataxia, a recessive neurodegenerative disease resulting from insufficient expression of the mitochondrial protein frataxin. however, the biochemical function of frataxin has remained obscure, hampering attempts at therapeutic intervention. to predict functional interactions of frataxin with other proteins we investigated whether its gene specifically co-occurs with any other genes in sequenced genomes. in 56 available genomes we ... | 2001 | 11689493 |
| reduction of bacterial genome size and expansion resulting from obligate intracellular lifestyle and adaptation to soil habitat. | prokaryotic organisms are exposed in the course of evolution to various impacts, resulting often in drastic changes of their genome size. depending on circumstances, the same lineage may diverge into species having substantially reduced genomes, or such whose genomes have undergone considerable enlargement. genome reduction is a consequence of obligate intracellular lifestyle rendering numerous genes expendable. another consequence of intracellular lifestyle is reduction of effective population ... | 2001 | 11732608 |
| the process of genome shrinkage in the obligate symbiont buchnera aphidicola. | very small genomes have evolved repeatedly in eubacterial lineages that have adopted obligate associations with eukaryotic hosts. complete genome sequences have revealed that small genomes retain very different gene sets, raising the question of how final genome content is determined. to examine the process of genome reduction, the tiny genome of the endosymbiont buchnera aphidicola was compared to the larger ancestral genome, reconstructed on the basis of the phylogenetic distribution of gene o ... | 2001 | 11790257 |
| genome interdependence in insect-bacterium symbioses. | symbioses between unicellular and multicellular organisms have contributed significantly to the evolution of life on earth. as exemplified by several studies of bacterium-insect symbioses, modern genomic techniques are providing exciting new information about the molecular basis and the biological roles of these complex relationships, revealing for instance that symbionts have lost many genes for functions that are provided by the host, but that they can provide amino acids that the host cannot ... | 2001 | 11790259 |
| an experimental validation of orphan genes of buchnera, a symbiont of aphids. | although buchnera sp. aps, an intracellular symbiont of pea aphids, is a close relative of escherichia coli, its genome has been extensively modified because of its prolonged intracellular life. in our previous studies on the buchnera genome, computer analysis predicted three "orphan" genes, yba2, yba3, and yba4, which are open reading frames (orfs) with no homologs in the database. in this paper, we successfully validated all these orphan genes by rt-pcr and northern hybridization. the present ... | 2002 | 11890702 |
| extreme genome reduction in buchnera spp.: toward the minimal genome needed for symbiotic life. | buchnera is a mutualistic intracellular symbiont of aphids. their association began about 200 million years ago, with host and symbiont lineages evolving in parallel since that time. during this coevolutionary process, buchnera has experienced a dramatic decrease of genome size, retaining only essential genes for its specialized lifestyle. previous studies reported that genome size in buchnera spp. is very uniform, suggesting that genome shrinkage occurred early in evolution, and that modern lin ... | 2002 | 11904373 |
| molecular characterization of the leucine cluster in buchnera sp. strain psy, a primary endosymbiont of the aphid pemphigus spyrothecae. | buchnera strains from most aphid subfamilies studied to date have been found to carry the leucine gene cluster (leua, -b, -c, and -d) on a plasmid, an organization unique among bacteria. here, however, we demonstrate a classical chromosomal location of the cluster in buchnera sp. strain psy from the aphid pemphigus spyrothecae (subfamily pemphiginae). the genes that flank leuabcd in buchnera sp. strain psy appear to be adjacent in the genome of buchnera sp. strain aps, a strain carrying a leucin ... | 2002 | 11976137 |
| the evolution of the heat-shock protein groel from buchnera, the primary endosymbiont of aphids, is governed by positive selection. | the heat-shock protein groel is a double-ring-structured chaperonin that assists the folding of many newly synthesized proteins in escherichia coli and the refolding in vitro, with the cochaperonin groes, of conformationally damaged proteins. this protein is constitutively overexpressed in the primary symbiotic bacteria of many insects, constituting approximately 10% of the total protein in buchnera, the primary endosymbiont of aphids. in the present study, we perform a maximum likelihood (ml) a ... | 2002 | 12082135 |
| estimating population size and transmission bottlenecks in maternally transmitted endosymbiotic bacteria. | many species of bacterial endosymbionts are acquired by animal hosts before birth, through direct transmission from mothers to eggs or embryos. this vertical transmission imposes a reduction in numbers or "bottleneck," and the size of this bottleneck affects the population structure and evolution of symbiotic lineages. we have estimated the size of the transmission bottleneck in buchnera, the bacterial symbiont of aphids, using basic light and electron microscopy techniques. by serial-sectioning ... | 2002 | 12087426 |
| the genetic properties of the primary endosymbionts of mealybugs differ from those of other endosymbionts of plant sap-sucking insects. | mealybugs (hemiptera, coccoidea, pseudococcidae), like aphids and psyllids, are plant sap-sucking insects that have an obligate association with prokaryotic endosymbionts that are acquired through vertical, maternal transmission. we sequenced two fragments of the genome of tremblaya princeps, the endosymbiont of mealybugs, which is a member of the beta subdivision of the proteobacteria. each of the fragments (35 and 30 kb) contains a copy of 16s-23s-5s rrna genes. a total of 37 open reading fram ... | 2002 | 12088995 |
| 50 million years of genomic stasis in endosymbiotic bacteria. | comparison of two fully sequenced genomes of buchnera aphidicola, the obligate endosymbionts of aphids, reveals the most extreme genome stability to date: no chromosome rearrangements or gene acquisitions have occurred in the past 50 to 70 million years, despite substantial sequence evolution and the inactivation and loss of individual genes. in contrast, the genomes of their closest free-living relatives, escherichia coli and salmonella spp., are more than 2000-fold more labile in content and g ... | 2002 | 12089438 |
| comparative molecular evolution of primary (buchnera) and secondary symbionts of aphids based on two protein-coding genes. | a+t content, phylogenetic relationships, codon usage, evolutionary rates, and ratio of synonymous versus non-synonymous substitutions have been studied in partial sequences of the atpd and aroq/phea genes of primary ( buchnera) and secondary symbionts of aphids and a set of selected non-symbiotic bacteria, belonging to the five subdivisions of the proteobacteria. compared to the homologous genes of the last group, both genes belonging to buchnera behave in a similar way, showing a higher a+t con ... | 2002 | 12107590 |
| searching for clues. | | 2002 | 12160625 |
| genome deterioration: loss of repeated sequences and accumulation of junk dna. | a global survey of microbial genomes reveals a correlation between genome size, repeat content and lifestyle. free-living bacteria have large genomes with a high content of repeated sequences and self-propagating dna, such as transposons and bacteriophages. in contrast, obligate intracellular bacteria have small genomes with a low content of repeated sequences and no or few genetic parasites. in extreme cases, such as in the 650 kb-genomes of aphid endosymbionts of the genus buchnera all repeate ... | 2002 | 12188042 |
| a strong effect of at mutational bias on amino acid usage in buchnera is mitigated at high-expression genes. | the advent of full genome sequences provides exceptionally rich data sets to explore molecular and evolutionary mechanisms that shape divergence among and within genomes. in this study, we use multivariate analysis to determine the processes driving genome-wide patterns of amino usage in the obligate endosymbiont buchnera and its close free-living relative escherichia coli. in the at-rich buchnera genome, the primary source of variation in amino acid usage differentiates high- and low-expression ... | 2002 | 12200484 |
| acceleration of genomic evolution caused by enhanced mutation rate in endocellular symbionts. | endosymbionts, which are widely observed in nature, have undergone reductive genome evolution because of their long-term intracellular lifestyle. here we compared the complete genome sequences of two different endosymbionts, buchnera and a protist mitochondrion, with their close relatives to study the evolutionary rates of functional genes in endosymbionts. the results indicate that the rate of amino acid substitution is two times higher in symbionts than in their relatives. this rate increase w ... | 2002 | 12235368 |
| diversity and geographic distribution of secondary endosymbiotic bacteria in natural populations of the pea aphid, acyrthosiphon pisum. | in addition to the essential intracellular symbiotic bacterium buchnera, several facultative endosymbiotic bacteria called collectively secondary symbionts (s-symbionts) have been identified from the pea aphid acyrthosiphon pisum. we conducted an extensive and systematic survey of s-symbionts in japanese local populations of a. pisum using a specific pcr detection technique. five s-symbionts of a. pisum, pass, paus, pabs, rickettsia and spiroplasma, and two facultative endosymbionts universally ... | 2002 | 12296954 |