Publications
| Title | Abstract | Year Filter | PMID(sorted descending) Filter |
|---|
| evolutionary relationships of "candidatus riesia spp.," endosymbiotic enterobacteriaceae living within hematophagous primate lice. | the primary endosymbiotic bacteria from three species of parasitic primate lice were characterized molecularly. we have confirmed the characterization of the primary endosymbiont (p-endosymbiont) of the human head/body louse pediculus humanus and provide new characterizations of the p-endosymbionts from pediculus schaeffi from chimpanzees and pthirus pubis, the pubic louse of humans. the endosymbionts show an average percent sequence divergence of 11 to 15% from the most closely related known ba ... | 2007 | 17220259 |
| role of host nutrition in symbiont regulation: impact of dietary nitrogen on proliferation of obligate and facultative bacterial endosymbionts of the pea aphid acyrthosiphon pisum. | the impact of host nutrition on symbiont regulation in the pea aphid acyrthosiphon pisum was investigated. the population density of the obligate symbiont buchnera aphidicola positively correlated with dietary nitrogen levels. in contrast, the population density of the facultative symbiont serratia symbiotica increased in aphids reared on low-nitrogen diets, indicating distinct regulatory mechanisms in the same insect host. | 2007 | 17158610 |
| dynamics of reductive genome evolution in mitochondria and obligate intracellular microbes. | reductive evolution in mitochondria and obligate intracellular microbes has led to a significant reduction in their genome size and guanine plus cytosine content (gc). we show that genome shrinkage during reductive evolution in prokaryotes follows an exponential decay pattern and provide a method to predict the extent of this decay on an evolutionary timescale. we validated predictions by comparison with estimated extents of genome reduction known to have occurred in mitochondria and buchnera ap ... | 2007 | 17108184 |
| genome reduction of the aphid endosymbiont buchnera aphidicola in a recent evolutionary time scale. | genome reduction, a typical feature of symbiotic bacteria, was analyzed in the last stages of evolution of buchnera aphidicola, the primary aphid endosymbiont, in two neutrally evolving regions: the pseudogene cmk and an intergenic region. these two regions were examined in endosymbionts from several lineages of their aphid host rhopalosiphum padi, and different species of the same genus, whose divergence times ranged from 0.62 to 19.51 million years. estimates of nucleotide substitution rates w ... | 2007 | 17098378 |
| selection acts on dna secondary structures to decrease transcriptional mutagenesis. | single-stranded dna is more subject to mutation than double stranded. during transcription, dna is transiently single stranded and therefore subject to higher mutagenesis. however, if local intra-strand secondary structures are formed, some bases will be paired and therefore less sensitive to mutation than unpaired bases. using complete genome sequences of escherichia coli, we show that local intra-strand secondary structures can, as a consequence, be used to define an index of transcription-dri ... | 2006 | 17083275 |
| different levels of transcriptional regulation due to trophic constraints in the reduced genome of buchnera aphidicola aps. | symbiotic associations involving intracellular microorganisms and animals are widespread, especially for species feeding on poor or unbalanced diets. buchnera aphidicola, the obligate intracellular bacterium associated with most aphid species, provides its hosts with essential amino acids (eaas), nutrients in short supply in the plant phloem sap. the buchnera genome has undergone severe reductions during intracellular evolution. genes for eaa biosynthesis are conserved, but most of the transcrip ... | 2006 | 17041159 |
| the reach of the genome signature in prokaryotes. | with the increased availability of sequenced genomes there have been several initiatives to infer evolutionary relationships by whole genome characteristics. one of these studies suggested good congruence between genome synteny, shared gene content, 16s ribosomal dna identity, codon usage and the genome signature in prokaryotes. here we rigorously test the phylogenetic signal of the genome signature, which consists of the genome-specific relative frequencies of dinucleotides, on 334 sequenced pr ... | 2006 | 17040564 |
| a small microbial genome: the end of a long symbiotic relationship? | intracellular bacteria are characterized by genome reduction. the 422,434-base pair genome of buchnera aphidicola bcc, primary endosymbiont of the aphid cinara cedri, is approximately 200 kilobases smaller than the previously sequenced b. aphidicola genomes. b. aphidicola bcc has lost most metabolic functions, including the ability to synthesize the essential amino acid tryptophan and riboflavin. in addition, most retained genes are evolving rapidly. possibly, b. aphidicola bcc is losing its sym ... | 2006 | 17038625 |
| genetics. the bacterial world gets smaller. | 2006 | 17038609 | |
| strict host-symbiont cospeciation and reductive genome evolution in insect gut bacteria. | host-symbiont cospeciation and reductive genome evolution have been identified in obligate endocellular insect symbionts, but no such example has been identified from extracellular ones. here we first report such a case in stinkbugs of the family plataspidae, wherein a specific gut bacterium is vertically transmitted via "symbiont capsule." in all of the plataspid species, females produced symbiont capsules upon oviposition and their gut exhibited specialized traits for capsule production. phylo ... | 2006 | 17032065 |
| codon usage bias and trna over-expression in buchnera aphidicola after aromatic amino acid nutritional stress on its host acyrthosiphon pisum. | codon usage bias and relative abundances of trna isoacceptors were analysed in the obligate intracellular symbiotic bacterium, buchnera aphidicola from the aphid acyrthosiphon pisum, using a dedicated 35mer oligonucleotide microarray. buchnera is archetypal of organisms living with minimal metabolic requirements and presents a reduced genome with high-evolutionary rate. codonusage in buchnera has been overcome by the high mutational bias towards at bases. however, several lines of evidence for c ... | 2006 | 16963497 |
| hundreds of flagellar basal bodies cover the cell surface of the endosymbiotic bacterium buchnera aphidicola sp. strain aps. | buchnera aphidicola is the endosymbiotic bacterium of the pea aphid. due to its small genome size, buchnera lacks many essential genes for autogenous life but obtains nutrients from the host. although the buchnera cell is nonmotile, it retains clusters of flagellar genes that lack the late genes necessary for motility, including the flagellin gene. in this study, we show that the flagellar genes are actually transcribed and translated and that the buchnera cell surface is covered with hundreds o ... | 2006 | 16952945 |
| muller's ratchet in symbiont populations. | muller's ratchet, the inevitable accumulation of deleterious mutations in asexual populations, has been proposed as a major factor in genome degradation of obligate symbiont organisms. essentially, if left unchecked the ratchet will with certainty cause extinction due to the ever increasing mutational load. this paper examines the evolutionary fate of insect symbionts, using mathematical modelling to simulate the accumulation of deleterious mutations. we investigate the effects of a hierarchical ... | 2007 | 16924405 |
| tempo and mode of early gene loss in endosymbiotic bacteria from insects. | understanding evolutionary processes that drive genome reduction requires determining the tempo (rate) and the mode (size and types of deletions) of gene losses. in this study, we analysed five endosymbiotic genome sequences of the gamma-proteobacteria (three different buchnera aphidicola strains, wigglesworthia glossinidia, blochmannia floridanus) to test if gene loss could be driven by the selective importance of genes. we used a parsimony method to reconstruct a minimal ancestral genome of in ... | 2006 | 16848891 |
| costs and benefits of a superinfection of facultative symbionts in aphids. | symbiotic associations between animals and inherited micro-organisms are widespread in nature. in many cases, hosts may be superinfected with multiple inherited symbionts. acyrthosiphon pisum (the pea aphid) may harbour more than one facultative symbiont (called secondary symbionts) in addition to the obligate primary symbiont, buchnera aphidicola. previously we demonstrated that, in a controlled genetic background, a. pisum infected with either serratia symbiotica or hamiltonella defensa (calle ... | 2006 | 16720402 |
| functional genomics of buchnera and the ecology of aphid hosts. | in many animal groups, mutualistic bacterial symbionts play a central role in host ecology, by provisioning rare nutrients and thus enabling specialization on restricted diets. among such symbionts, genomic studies are most advanced for buchnera, the obligate symbiont of aphids, which feed on phloem sap. the contents of the highly reduced buchnera genomes have verified its role in aphid nutrition. comparisons of buchnera gene sets indicate ongoing, irreversible gene losses that are expected to a ... | 2006 | 16626452 |
| chance and necessity in the evolution of minimal metabolic networks. | it is possible to infer aspects of an organism's lifestyle from its gene content. can the reverse also be done? here we consider this issue by modelling evolution of the reduced genomes of endosymbiotic bacteria. the diversity of gene content in these bacteria may reflect both variation in selective forces and contingency-dependent loss of alternative pathways. using an in silico representation of the metabolic network of escherichia coli, we examine the role of contingency by repeatedly simulat ... | 2006 | 16572170 |
| a dual-genome microarray for the pea aphid, acyrthosiphon pisum, and its obligate bacterial symbiont, buchnera aphidicola. | the best studied insect-symbiont system is that of aphids and their primary bacterial endosymbiont buchnera aphidicola. buchnera inhabits specialized host cells called bacteriocytes, provides nutrients to the aphid and has co-speciated with its aphid hosts for the past 150 million years. we have used a single microarray to examine gene expression in the pea aphid, acyrthosiphon pisum, and its resident buchnera. very little is known of gene expression in aphids, few studies have examined gene exp ... | 2006 | 16536873 |
| partitioning of symbiotic bacteria between generations of an insect: a quantitative study of a buchnera sp. in the pea aphid (acyrthosiphon pisum) reared at different temperatures. | the population of symbiotic buchnera bacteria in parthenogenetic females of the pea aphid acyrthosiphon pisum was determined by quantitative hybridization of a dna probe (groesl) to aphid homogenates. the aphids bore 1 x 10(sup7) to 2 x 10(sup7) bacterial cells per mg (fresh weight). in teneral aphids (i.e., aphids that had moulted to adulthood but that had not initiated reproduction), >75% of the bacteria were in the embryos, and the density of bacteria in the embryos was consistently greater t ... | 1997 | 16535678 |
| mutualistic associations of aphids and prokaryotes: biology of the genus buchnera. | 1995 | 16534896 | |
| strong asymmetric mutation bias in endosymbiont genomes coincide with loss of genes for replication restart pathways. | a large majority of bacterial genomes show strand asymmetry, such that g and t preferentially accumulate on the leading strand. the mechanisms are unknown, but cytosine deaminations are thought to play an important role. here, we have examined dna strand asymmetry in three strains of the aphid endosymbiont buchnera aphidicola. these are phylogenetically related, have similar genomic gc contents, and conserved gene order structures, yet b. aphidicola (bp) shows a fourfold higher replication-induc ... | 2006 | 16476690 |
| phloem-sap feeding by animals: problems and solutions. | the incidence of phloem sap feeding by animals appears paradoxical. although phloem sap is nutrient-rich compared with many other plant products and generally lacking in toxins and feeding deterrents, it is consumed as the dominant or sole diet by a very restricted range of animals, exclusively insects of the order hemiptera. these insects display two sets of adaptations. first, linked to the high ratio of non-essential:essential amino acids in phloem sap, these insects contain symbiotic micro-o ... | 2006 | 16449374 |
| plasmids in the aphid endosymbiont buchnera aphidicola with the smallest genomes. a puzzling evolutionary story. | buchnera aphidicola, the primary endosymbiont of aphids, has undergone important genomic and biochemical changes as an adaptation to intracellular life. the most important structural changes include a drastic genome reduction and the amplification of genes encoding key enzymes for the biosynthesis of amino acids by their translocation to plasmids. molecular characterization through different aphid subfamilies has revealed that the genes involved in leucine and tryptophan biosynthesis show a vari ... | 2006 | 16413149 |
| buchnerabase: a post-genomic resource for buchnera sp. aps. | summary: buchnerabase is a bioinformatic research tool for the genome of the symbiotic bacterium buchnera sp. aps that includes an improved genome annotation, comparative information about related insect symbiont genomes and a complete mapping of metabolic reactions to an escherichia coli in silico model. the database is designed to accommodate genome-wide post-genomic datasets that are becoming available for this organism. availability: buchnerabase is available at http://www.buchnera.org/. | 2006 | 16397006 |
| occurrence of nitric oxide synthase in megoura viciae buckton (homoptera, aphididae): an histochemical and immunohistochemical localisation. | nitric oxide (no) is known to be involved in many physiological reactions of insects. we analysed nos localisation in aphids of the species megoura viciae by means of histochemical reaction for the nadph-diaphorase activity and immunohistochemical methods for unos, nnos and inos. the obtained data provided a complex and peculiar pattern of nos distribution in cells and tissue of m. viciae. the histochemical reaction for nadph-diaphorase was an indicative, but not exact marker of nos localisation ... | 2005 | 16377581 |
| growth kinetics of the endosymbiont buchnera aphidicola in the aphid schizaphis graminum. | the aphid schizaphis graminum is dependent on its prokaryotic endosymbiont, buchnera aphidicola. as a means of determining b. aphidicola numbers during the growth cycle of the aphid we have used the quantitative pcr to measure the number of copies of rrs (the gene coding for 16s rrna, which is present as one copy in the b. aphidicola genome). in addition we have measured the aphid wet weight and the dna and protein content. the results indicate an approximately parallel (23- to 31-fold) increase ... | 1994 | 16349393 |
| the players in a mutualistic symbiosis: insects, bacteria, viruses, and virulence genes. | aphids maintain mutualistic symbioses involving consortia of coinherited organisms. all possess a primary endosymbiont, buchnera, which compensates for dietary deficiencies; many also contain secondary symbionts, such as hamiltonella defensa, which confers defense against natural enemies. genome sequences of uncultivable secondary symbionts have been refractory to analysis due to the difficulties of isolating adequate dna samples. by amplifying dna from hemolymph of infected pea aphids, we obtai ... | 2005 | 16195380 |
| chromosomal stasis versus plasmid plasticity in aphid endosymbiont buchnera aphidicola. | the study of three genomes of the aphid endosymbiont buchnera aphidicola has revealed an extraordinary stasis: conservation of gene order and genetic composition of the chromosome, while the chromosome size and number of genes has reduced. the reduction in genome size appears to be ongoing since some lineages we now know to have even smaller chromosomes than the first b. aphidicola analysed. the current sequencing by our group of one of these smaller genomes with an estimated size of 450 kb, and ... | 2005 | 16118664 |
| genome sequence of blochmannia pennsylvanicus indicates parallel evolutionary trends among bacterial mutualists of insects. | the distinct lifestyle of obligately intracellular bacteria can alter fundamental forces that drive and constrain genome change. in this study, sequencing the 792-kb genome of blochmannia pennsylvanicus, an obligate endosymbiont of camponotus pennsylvanicus, enabled us to trace evolutionary changes that occurred in the context of a bacterial-ant association. comparison to the genome of blochmannia floridanus reveals differential loss of genes involved in cofactor biosynthesis, the composition an ... | 2005 | 16077009 |
| the roles of positive and negative selection in the molecular evolution of insect endosymbionts. | the evolutionary rate acceleration observed in most endosymbiotic bacteria may be explained by higher mutation rates, changes in selective pressure, and increased fixation of deleterious mutations by genetic drift. here, we explore the forces influencing molecular evolution in blochmannia, an obligate endosymbiont of camponotus and related ant genera. our goals were to compare rates of sequence evolution in blochmannia with related bacteria, to explore variation in the strength and efficacy of n ... | 2005 | 16039807 |
| rickettsia symbiont in the pea aphid acyrthosiphon pisum: novel cellular tropism, effect on host fitness, and interaction with the essential symbiont buchnera. | in natural populations of the pea aphid acyrthosiphon pisum, a facultative bacterial symbiont of the genus rickettsia has been detected at considerable infection frequencies worldwide. we investigated the effects of the rickettsia symbiont on the host aphid and also on the coexisting essential symbiont buchnera. in situ hybridization revealed that the rickettsia symbiont was specifically localized in two types of host cells specialized for endosymbiosis: secondary mycetocytes and sheath cells. e ... | 2005 | 16000822 |
| regulation of transcription in a reduced bacterial genome: nutrient-provisioning genes of the obligate symbiont buchnera aphidicola. | buchnera aphidicola, the obligate symbiont of aphids, has an extremely reduced genome, of which about 10% is devoted to the biosynthesis of essential amino acids needed by its hosts. most regulatory genes for these pathways are absent, raising the question of whether and how transcription of these genes responds to the major shifts in dietary amino acid content encountered by aphids. using full-genome microarrays for b. aphidicola of the host schizaphis graminum, we examined transcriptome respon ... | 2005 | 15937185 |
| gene expression levels influence amino acid usage and evolutionary rates in endosymbiotic bacteria. | most endosymbiotic bacteria have extremely reduced genomes, accelerated evolutionary rates, and strong at base compositional bias thought to reflect reduced efficacy of selection and increased mutational pressure. here, we present a comparative study of evolutionary forces shaping five fully sequenced bacterial endosymbionts of insects. the results of this study were three-fold: (i) stronger conservation of high expression genes at not just nonsynonymous, but also synonymous, sites. (ii) variati ... | 2005 | 15935576 |
| endosymbiosis: past and present. | 2005 | 15931237 | |
| comparative study of overlapping genes in bacteria, with special reference to rickettsia prowazekii and rickettsia conorii. | overlapping genes have been proposed as a means of achieving genome reduction by compressing the maximum amount of information in limited sequence space. in this report, comparative analyses of the overlapping genes of genomes of nine bacteria with different lifestyles were performed. the results clearly suggest that overlapping genes may be a result of evolutionary pressure to minimize genome size. the genomes of two closely related obligatory intracellular parasites - rickettsia prowazekii and ... | 2005 | 15879256 |
| transcriptome analysis of the aphid bacteriocyte, the symbiotic host cell that harbors an endocellular mutualistic bacterium, buchnera. | aphids possess bacteriocytes, cells specifically differentiated to harbor obligatory mutualistic bacteria of the genus buchnera, which have lost many genes that are essential for common bacterial functions. to understand the host's role in maintaining the symbiotic relationship, bacteriocytes were isolated from the pea aphid, acyrthosiphon pisum, and the host transcriptome was investigated by using est analysis and real-time quantitative rt-pcr. a number of genes were highly expressed specifical ... | 2005 | 15800043 |
| genome rearrangement distances and gene order phylogeny in gamma-proteobacteria. | genome rearrangements have been studied in 30 gamma-proteobacterial complete genomes by comparing the order of a reduced set of genes on the chromosome. this set included those genes fulfilling several characteristics, the main ones being that an ortholog was present in every genome and that none of them had been acquired by horizontal gene transfer. genome rearrangement distances were estimated based on either the number of breakpoints or the minimal number of inversions separating two genomes. ... | 2005 | 15772379 |
| comparative analysis of two genomic regions among four strains of buchnera aphidicola, primary endosymbiont of aphids. | preliminary analysis of two selected genomic regions of buchnera aphidicola bcc, the primary endosymbiont of the cedar aphid cinara cedri, has revealed a number of interesting features when compared with the corresponding homologous regions of the three b. aphidicola genomes previously sequenced, that are associated with different aphid species. both regions exhibit a significant reduction in length and gene number in b. aphidicola bcc, as it could be expected since it possess the smallest bacte ... | 2004 | 15716086 |
| mutation exposed: a neutral explanation for extreme base composition of an endosymbiont genome. | the influence of neutral mutation pressure versus selection on base composition evolution is a subject of considerable controversy. yet the present study represents the first explicit population genetic analysis of this issue in prokaryotes, the group in which base composition variation is most dramatic. here, we explore the impact of mutation and selection on the dynamics of synonymous changes in buchnera aphidicola, the at-rich bacterial endosymbiont of aphids. specifically, we evaluated three ... | 2004 | 15599516 |
| metabolic interdependence of obligate intracellular bacteria and their insect hosts. | mutualistic associations of obligate intracellular bacteria and insects have attracted much interest in the past few years due to the evolutionary consequences for their genome structure. however, much less attention has been paid to the metabolic ramifications for these endosymbiotic microorganisms, which have to compete with but also to adapt to another metabolism--that of the host cell. this review attempts to provide insights into the complex physiological interactions and the evolution of m ... | 2004 | 15590782 |
| nonhomogeneous model of sequence evolution indicates independent origins of primary endosymbionts within the enterobacteriales (gamma-proteobacteria). | standard methods of phylogenetic reconstruction are based on models that assume homogeneity of nucleotide composition among taxa. however, this assumption is often violated in biological data sets. in this study, we examine possible effects of nucleotide heterogeneity among lineages on the phylogenetic reconstruction of a bacterial group that spans a wide range of genomic nucleotide contents: obligately endosymbiotic bacteria and free-living or commensal species in the gamma-proteobacteria. we f ... | 2005 | 15525700 |
| coexistence of wolbachia with buchnera aphidicola and a secondary symbiont in the aphid cinara cedri. | intracellular symbiosis is very common in the insect world. for the aphid cinara cedri, we have identified by electron microscopy three symbiotic bacteria that can be characterized by their different sizes, morphologies, and electrodensities. pcr amplification and sequencing of the 16s ribosomal dna (rdna) genes showed that, in addition to harboring buchnera aphidicola, the primary endosymbiont of aphids, c. cedri harbors a secondary symbiont (s symbiont) that was previously found to be associat ... | 2004 | 15375144 |
| the evolutionary fate of nonfunctional dna in the bacterial endosymbiont buchnera aphidicola. | reduction of the genome size in endosymbiotic bacteria is the main feature linked to the adaptation to a host-associated lifestyle. we have analyzed the fate of the nonfunctional dna in buchnera aphidicola, the primary endosymbiont of aphids. at least 164 gene losses took place during the recent evolution of three b. aphidicola strains, symbionts of the aphids acyrthosiphon pisum (bap), schizaphis graminum (bsg), and baizongia pistacia (bbp). a typical pattern starts with the inactivation of a g ... | 2004 | 15317875 |
| evolutionary relatedness between glycolytic enzymes most frequently occurring in genomes. | more than 100 sequenced genomes were searched for genes coding for the enzymes involved in glycolysis in an effort to find the most frequently occurring ones. triosephosphate isomerase (tim), glyceraldehyde-3-phosphate dehydrogenase (gapd), phosphoglycerate kinase (pgk) and enolase (enol) were found to be present in 90 investigated genomes all together. the final set consisted of 80 prokaryotic and 10 eukaryotic genomes. of the 80 prokaryotic genomes, 73 were from bacteria, 7 from archaea. two m ... | 2004 | 15259764 |
| evolution of the leucine gene cluster in buchnera aphidicola: insights from chromosomal versions of the cluster. | in buchnera aphidicola strains associated with the aphid subfamilies thelaxinae, lachninae, pterocommatinae, and aphidinae, the four leucine genes (leua, -b, -c, and -d) are located on a plasmid. however, these genes are located on the main chromosome in b. aphidicola strains associated with the subfamilies pemphiginae and chaitophorinae. the sequence of the chromosomal fragment containing the leucine cluster and flanking genes has different positions in the chromosome in b. aphidicola strains a ... | 2004 | 15090505 |
| assessment of 35mer amino-modified oligonucleotide based microarray with bacterial samples. | parallel quantification of a large number of messenger rna transcripts, using microarray technology, promises to provide unsuspected information about many cellular processes. although experimental protocols on microarray applications are available, only limited methodological information on glass-slide manufacturing and signal interpretation has been published. the aim of this paper is to provide new insights into the practical aspects of the construction and hybridization of oligonucleotide-ba ... | 2004 | 15063061 |
| use of the genomic signature in bacterial classification and identification. | in this study we investigated the correlation between dinucleotide relative abundance values (the genomic signature) obtained from bacterial whole-genome sequences and two parameters widely used for bacterial classification, 16s rdna sequence similarity and dna-dna hybridisation values. twenty-eight completely sequenced bacterial genomes were included in the study. the correlation between the genomic signature and dna-dna hybridisation values was high and taxa that showed less than 30% dna-dna b ... | 2004 | 15046306 |
| the relationship between palindrome avoidance and intragenic codon usage variations: a monte carlo study. | several studies have shown that codon usage within genes varies, as it seems dependent on both codon context and codon position within the gene. given that palindromes in addition often are avoided in genomes, this study aimed at finding out if intragenic variations in codon usage may be a way to control the amount and location of palindromes. a monte carlo algorithm was written which resampled the codons in genes while keeping the amino acid sequence of the translation product constant. on the ... | 2004 | 15033465 |
| molecular systematics of aphids (homoptera: aphididae): new insights from the long-wavelength opsin gene. | viviparous aphids (aphididae) constitute a monophyletic group within the homoptera with more than 4000 extant species worldwide but higher diversity in temperate regions. several aspects of their biology account for attention paid to this group of insects. their plant-sap-sucking way of feeding with many species transmitting viruses to crop plants has important implications on crop management strategies. cyclical parthenogenesis associated in many groups to host alternation and elaborate polyphe ... | 2004 | 15022755 |
| a phylogenomic study of endosymbiotic bacteria. | endosymbiotic bacteria of aphids, buchnera aphidicola, and tsetse flies, wigglesworthia glossinidia, are descendents of free-living gamma-proteobacteria. the acceleration of sequence evolution in the endosymbiont genomes is here estimated from a phylogenomic analysis of the gamma-proteobacteria. the tree topologies associated with the most highly conserved genes suggest that the endosymbionts form a sister group with escherichia coli, salmonella sp., and yersinia pestis. our results indicate tha ... | 2004 | 15014155 |
| nutritional interactions in insect-microbial symbioses: aphids and their symbiotic bacteria buchnera. | most aphids possess intracellular bacteria of the genus buchnera. the bacteria are transmitted vertically via the aphid ovary, and the association is obligate for both partners: bacteria-free aphids grow poorly and produce few or no offspring, and buchnera are both unknown apart from aphids and apparently unculturable. the symbiosis has a nutritional basis. specifically, bacterial provisioning of essential amino acids has been demonstrated. nitrogen recycling, however, is not quantitatively impo ... | 1998 | 15012383 |
| host-symbiont stability and fast evolutionary rates in an ant-bacterium association: cospeciation of camponotus species and their endosymbionts, candidatus blochmannia. | bacterial endosymbionts are widespread across several insect orders and are involved in interactions ranging from obligate mutualism to reproductive parasitism. candidatus blochmannia gen. nov. (blochmannia) is an obligate bacterial associate of camponotus and related ant genera (hymenoptera: formicidae). the occurrence of blochmannia in all camponotus species sampled from field populations and its maternal transmission to host offspring suggest that this bacterium is engaged in a long-term, sta ... | 2004 | 14965905 |
| changing partners in an obligate symbiosis: a facultative endosymbiont can compensate for loss of the essential endosymbiont buchnera in an aphid. | almost all aphids harbour an endosymbiotic bacterium, buchnera aphidicola, in bacteriocytes. buchnera synthesizes essential nutrients and supports growth and reproduction of the host. over the long history of endosymbiosis, many essential genes have been lost from the buchnera genome, resulting in drastic genome reduction and the inability to live outside the host cells. in turn, when deprived of buchnera, the host aphid suffers retarded growth and sterility. buchnera and the host aphid are ofte ... | 2003 | 14728775 |
| a conservative test of genetic drift in the endosymbiotic bacterium buchnera: slightly deleterious mutations in the chaperonin groel. | the obligate endosymbiotic bacterium buchnera aphidicola shows elevated rates of sequence evolution compared to free-living relatives, particularly at nonsynonymous sites. because buchnera experiences population bottlenecks during transmission to the offspring of its aphid host, it is hypothesized that genetic drift and the accumulation of slightly deleterious mutations can explain this rate increase. recent studies of intraspecific variation in buchnera reveal patterns consistent with this hypo ... | 2003 | 14704156 |
| evolution of minimal-gene-sets in host-dependent bacteria. | several attempts have been made to identify the minimal set of genes that is required for life using computational approaches or studies of deletion mutants. these experiments resemble those already performed by nature; a few hundred million years ago an ancestor of escherichia coli was domesticated by aphids, which resulted in the elimination of 70-75% of the original bacterial genome. amazingly, the small genomes of these imprisoned bacteria are more stable than those of their free-living rela ... | 2004 | 14700550 |
| mutational and selective pressures on codon and amino acid usage in buchnera, endosymbiotic bacteria of aphids. | we have explored compositional variation at synonymous (codon usage) and nonsynonymous (amino acid usage) positions in three complete genomes of buchnera, endosymbiotic bacteria of aphids, and also in their orthologs in escherichia coli, a close free-living relative. we sought to discriminate genes of variable expression levels in order to weigh the relative contributions of mutational bias and selection in the genomic changes following symbiosis. we identified clear strand asymmetries, distribu ... | 2004 | 14672975 |
| diversity of bacteria associated with natural aphid populations. | the bacterial communities of aphids were investigated by terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis analysis of 16s rrna gene fragments generated by pcr with general eubacterial primers. by both methods, the gamma-proteobacterium buchnera was detected in laboratory cultures of six parthenogenetic lines of the pea aphid acyrthosiphon pisum and one line of the black bean aphid aphis fabae, and one or more of four previously described bacterial tax ... | 2003 | 14660369 |
| chaos game representation of protein sequences based on the detailed hp model and their multifractal and correlation analyses. | similar to the chaos game representation (cgr) of dna sequences proposed by jeffrey (nucleic acid res. 18 (1990) 2163), a new cgr of protein sequences based on the detailed hp model is proposed. multifractal and correlation analyses of the measures based on the cgr of protein sequences from complete genomes are performed. the dq spectra of all organisms studied are multifractal-like and sufficiently smooth for the cq curves to be meaningful. the cq curves of bacteria resemble a classical phase t ... | 2004 | 14643648 |
| automatic annotation of protein function based on family identification. | although genomes are being sequenced at an impressive rate, the information generated tells us little about protein function, which is slow to characterize by traditional methods. automatic protein function annotation based on computational methods has alleviated this imbalance. the most powerful current approach for inferring the function of new proteins is by studying the annotations of their homologues, since their common origin is assumed to be reflected in their structure and function. unfo ... | 2003 | 14579359 |
| tracing the evolution of gene loss in obligate bacterial symbionts. | the gamma-proteobacterial symbionts of insects are a model group for comparative studies of genome reduction. the phylogenetic proximity of these reduced genomes to the larger genomes of well-studied free-living bacteria has enabled reconstructions of the process by which genes and dna are lost. three genome sequences are now available for buchnera aphidicola. analyses of buchnera genomes in comparison with those of related enteric bacteria suggest that extensive changes including large deletion ... | 2003 | 14572545 |
| developmental origin and evolution of bacteriocytes in the aphid-buchnera symbiosis. | symbiotic relationships between bacteria and insect hosts are common. although the bacterial endosymbionts have been subjected to intense investigation, little is known of the host cells in which they reside, the bacteriocytes. we have studied the development and evolution of aphid bacteriocytes, the host cells that contain the endosymbiotic bacteria buchnera aphidicola. we show that bacteriocytes of acyrthosiphon pisum express several gene products (or their paralogues): distal-less, ultrabitho ... | 2003 | 14551917 |
| a genomic perspective on nutrient provisioning by bacterial symbionts of insects. | many animals show intimate interactions with bacterial symbionts that provision hosts with limiting nutrients. the best studied such association is that between aphids and buchnera aphidicola, which produces essential amino acids that are rare in the phloem sap diet. genomic studies of buchnera have provided a new means for inferring metabolic capabilities of the symbionts and their likely contributions to hosts. despite evolutionary reduction of genome size, involving loss of most ancestral gen ... | 2003 | 14527994 |
| host-based divergence in populations of the pea aphid: insights from nuclear markers and the prevalence of facultative symbionts. | in north america, the pea aphid acyrthosiphon pisum encompasses ecologically and genetically distinct host races that offer an ideal biological system for studies on sympatric speciation. in addition to its obligate symbiont buchnera, pea aphids harbour several facultative and phylogenetically distant symbionts. we explored the relationships between host races of a. pisum and their symbiotic microbiota to gain insights into the historical process of ecological specialization and symbiotic acquis ... | 2003 | 12964998 |
| [identification of the horizontal gene transfer based on phylogenetic data]. | we suggest a new procedure to search for the genes with horizontal transfer events in their evolutionary history. the search is based on analysis of topology difference between the phylogenetic trees of gene (protein) groups and the corresponding phylogenetic species trees. numeric values are introduced to measure the discrepancy between the trees. this approach was applied to analyze 40 prokaryotic genomes classified into 132 classes of orthologs. this resulted in a list of the candidate genes ... | 2003 | 12942641 |
| the genome sequence of blochmannia floridanus: comparative analysis of reduced genomes. | bacterial symbioses are widespread among insects, probably being one of the key factors of their evolutionary success. we present the complete genome sequence of blochmannia floridanus, the primary endosymbiont of carpenter ants. although these ants feed on a complex diet, this symbiosis very likely has a nutritional basis: blochmannia is able to supply nitrogen and sulfur compounds to the host while it takes advantage of the host metabolic machinery. remarkably, these bacteria lack all known ge ... | 2003 | 12886019 |
| increased rates of sequence evolution in endosymbiotic bacteria and fungi with small effective population sizes. | mutualistic, maternally transmitted endosymbiotic microorganisms undergo severe population bottlenecks at each host generation, resulting in a reduction in effective population size (ne). previous studies of buchnera, the primary endosymbiont of aphids, and of several other species of endosymbiotic bacteria have shown that these species exhibit an increase in the rate of substitution of slightly deleterious mutations, among other predicted effects of increased drift due to small ne, such as redu ... | 2003 | 12832648 |
| consequences of reductive evolution for gene expression in an obligate endosymbiont. | the smallest cellular genomes are found in obligate symbiotic and pathogenic bacteria living within eukaryotic hosts. in comparison with large genomes of free-living relatives, these reduced genomes are rearranged and have lost most regulatory elements. to test whether reduced bacterial genomes incur reduced regulatory capacities, we used full-genome microarrays to evaluate transcriptional response to environmental stress in buchnera aphidicola, the obligate endosymbiont of aphids. the 580 genes ... | 2003 | 12791133 |
| provision of riboflavin to the host aphid, acyrthosiphon pisum, by endosymbiotic bacteria, buchnera. | differential cdna display and quantitative rt-pcr suggested that the riboflavin synthase complex of the aphid endosymbiont, buchnera, is active only when the symbiotic system is maintained and well organized in young hosts. since this finding suggested the provision of riboflavin by buchnera, we examined the effect of dietary riboflavin on the performance of symbiotic and aposymbiotic aphids using chemically-defined diets. our results indicate: (1) dietary riboflavin is slightly detrimental to y ... | 1999 | 12770389 |
| nutritional enhancement of host plants by aphids - a comparison of three aphid species on grasses. | three aphid species were compared with respect to ability of enhancing the nutritional quality of their host plants. rhopalosiphum padi, which does not induce macroscopic changes in its host plants, was compared with schizaphis graminum and diuraphis noxia, both of which induce distinctive types of chlorotic lesions. phloem sap samples were collected from severed stylets of feeding aphids and from exudates of cut leaves of plants uninfested or infested with each aphid species. samples were analy ... | 2000 | 12770256 |
| metabolic and symbiotic interactions in amino acid pools of the pea aphid, acyrthosiphon pisum, parasitized by the braconid aphidius ervi. | aphidius ervi haliday (hymenoptera, braconidae) is an endophagous parasitoid of the pea aphid, acyrthosiphon pisum (harris) (homoptera, aphididae). this parasitoid strongly redirects host reproduction and metabolism to favour nutrition and development of its juvenile stages. parasite-regulated biosynthesis and mobilization of nitrogen metabolites determine a significant increase of host nutritional suitability. the aim of the present study was mainly to investigate the temporal changes of a. pis ... | 2002 | 12770078 |
| host cell allometry and regulation of the symbiosis between pea aphids, acyrthosiphon pisum, and bacteria, buchnera. | the symbiotic bacteria buchnera in aphids are borne in cells, called bacteriocytes, in the insect haemocoel. the number and median volume of bacteriocytes in pre-reproductive adult insects varied significantly among 14 parthenogenetic clones of the pea aphid acyrthosiphon pisum. after logarithmic transformation of the data, the relationship of both number and median volume of bacteriocytes with aphid weight for the clones could be described by common regression lines with slopes significantly gr ... | 1998 | 12769945 |
| low and homogeneous copy number of plasmid-borne symbiont genes affecting host nutrition in buchnera aphidicola of the aphid uroleucon ambrosiae. | the bacterial endosymbiont of aphids, buchnera aphidicola, often provides amino acids to its hosts. plasmid amplification of leucine (leuabcd) and tryptophan (trpeg) biosynthesis genes may be a mechanism by which some buchnera over-produce these nutrients. we used quantitative polymerase chain reaction to assess the leuabcd/trpeg copy variability within uroleucon ambrosiae, an aphid with a wide diet breadth and range. both leuabcd and trpeg abundances are: (i) similar for aphids across 15 popula ... | 2003 | 12753227 |
| an appraisal of the potential for illegitimate recombination in bacterial genomes and its consequences: from duplications to genome reduction. | an exhaustive search for shortly spaced repeats in 74 bacterial chromosomes reveals that they are much more numerous than is usually acknowledged. these repeats were divided into five classes: close repeats (crs), tandem repeats (trs), simple sequence repeats (ssrs), spaced interspersed direct repeats, and "others." crs are widespread and constitute the most abundant class, particularly in coding sequences. the other classes are less frequent, but each individual element shows a higher potential ... | 2003 | 12743022 |
| why are the genomes of endosymbiotic bacteria so stable? | the comparative analysis of three strains of the endosymbiotic bacterium buchnera aphidicola has revealed high genome stability associated with an almost complete absence of chromosomal rearrangements and horizontal gene transfer events during the past 150 million years. the loss of genes involved in dna uptake and recombination in the initial stages of endosymbiosis probably underlies this stability. gene loss, which was extensive during the initial steps of buchnera evolution, has continued in ... | 2003 | 12683967 |
| extraordinary proliferation of microorganisms in aposymbiotic pea aphids, acyrthosiphon pisum. | aposymbiotic pea aphids, which were deprived of their intracellular symbiotic bacterium, buchnera, exhibit growth retardation and no fecundity. high performance liquid chromatographic (hplc) analysis revealed that these aposymbiotic aphids, when reared on broad bean plants, accumulated a large amount of histamine. to assess the possibility of extraordinary proliferation of microorganisms other than buchnera, we enumerated eubacteria and fungi in aphids using the real-time quantitative pcr method ... | 2003 | 12676551 |
| a matter of fitness. | 2003 | 12648939 | |
| facultative bacterial symbionts in aphids confer resistance to parasitic wasps. | symbiotic relationships between animals and microorganisms are common in nature, yet the factors controlling the abundance and distributions of symbionts are mostly unknown. aphids have an obligate association with the bacterium buchnera aphidicola (the primary symbiont) that has been shown to contribute directly to aphid fitness. in addition, aphids sometimes harbor other vertically transmitted bacteria (secondary symbionts), for which few benefits of infection have been previously documented. ... | 2003 | 12563031 |
| [cloning and prokaryotic expression of viral binding protein(vbp) gene from endosybiotic bacterium of rhopalosiphum padi]. | viral binding protein gene from rhopalosiphum padi yangling biotype was amplified by pcr method and then cloned. the complete nucleotide sequence of the gene was determined, it has 1647 nucleotides encoding 548 amino acids. comparison showed this gene has 97% identity on nucleotide level with buchnera groel-am gene of rhopalosiphum padi american biotype, while has 97.4% identity on amino acid level was found between this two genes. the vbp gene was ligated into pbv221 and pet30a expression vecto ... | 2002 | 12557551 |
| reductive genome evolution in buchnera aphidicola. | we have sequenced the genome of the intracellular symbiont buchnera aphidicola from the aphid baizongia pistacea. this strain diverged 80-150 million years ago from the common ancestor of two previously sequenced buchnera strains. here, a field-collected, nonclonal sample of insects was used as source material for laboratory procedures. as a consequence, the genome assembly unveiled intrapopulational variation, consisting of approximately 1,200 polymorphic sites. comparison of the 618-kb (kbp) g ... | 2003 | 12522265 |
| extremely low levels of genetic polymorphism in endosymbionts (buchnera) of aphids (pemphigus). | molecular evolutionary studies have suggested that vertically transmitted endosymbionts are subject to accumulation of deleterious mutations through genetic drift. predictions of this hypothesis for patterns of intraspecific polymorphism were borne out in the single relevant study available, on the symbiont buchnera aphidicola of uroleucon ambrosiae. in order to examine the generality of this result, we surveyed dna sequence variation in buchnera of the distantly related aphid, pemphigus obesiny ... | 2002 | 12453247 |
| genome evolution in bacterial endosymbionts of insects. | many insect species rely on intracellular bacterial symbionts for their viability and fecundity. large-scale dna-sequence analyses are revealing the forces that shape the evolution of these bacterial associates and the genetic basis of their specialization to an intracellular lifestyle. the full genome sequences of two obligate mutualists, buchnera aphidicola of aphids and wigglesworthia glossinidia of tsetse flies, reveal substantial gene loss and an integration of host and symbiont metabolic f ... | 2002 | 12415315 |
| comparative genomics of microbial pathogens and symbionts. | we are interested in quantifying the contribution of gene acquisition, loss, expansion and rearrangements to the evolution of microbial genomes. here, we discuss factors influencing microbial genome divergence based on pair-wise genome comparisons of closely related strains and species with different lifestyles. a particular focus is on intracellular pathogens and symbionts of the genera rickettsia, bartonella and buchnera: extensive gene loss and restricted access to phage and plasmid pools may ... | 2002 | 12385978 |
| 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 |
| 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 |
| 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 |
| 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 |
| searching for clues. | 2002 | 12160625 | |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 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 |
| 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 |