Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
|---|
| cooperative organization of bacterial colonies: from genotype to morphotype. | in nature, bacteria must often cope with difficult environmental conditions. to do so they have developed sophisticated cooperative behavior and intricate communication pathways. utilizing these elements, motile microbial colonies frequently develop complex patterns in response to adverse growth conditions on hard surfaces under conditions of energy limitation. we employ the term morphotype to refer to specific properties of colonial development. the morphologies we discuss include a tip-splitti ... | 1998 | 9891813 |
| a dnak homolog in myxococcus xanthus is involved in social motility and fruiting body formation. | myxococcus xanthus is a gram-negative soil bacterium which exhibits a complex life cycle and social behavior. in this study, two developmental mutants of m. xanthus were isolated through tn5 transposon mutagenesis. the mutants were found to be defective in cellular aggregation as well as in sporulation. further phenotypic characterization indicated that the mutants were defective in social motility but normal in directed cell movements. both mutations were cloned by a transposon-tagging method. ... | 1998 | 9440508 |
| myxococcus xanthus displays frz-dependent chemokinetic behavior during vegetative swarming. | myxococcus xanthus has been shown to utilize both directed (tactic) and undirected (kinetic) movements during different stages of its complex life cycle. we have used time-lapse video microscopic analysis to separate tactic and kinetic behaviors associated specifically with vegetatively swarming cells. isolated individual cells separated by a thin agar barrier from mature swarms showed significant increases in gliding velocity compared to that of similar cells some distance from the swarm. this ... | 1998 | 9440539 |
| genetic determinants of immunity and integration of temperate myxococcus xanthus phage mx8. | an 8.1-kb fragment of the temperate myxococcus xanthus phage mx8 genome, when cloned into a plasmid vector, permits site-specific integration of the plasmid and confers superinfection immunity. sequence analysis of a 9.5-kb region of mx8 dna containing this fragment reveals 19 densely packed open reading frames, four of which have predicted products with known or suspected activities. the mx8 imm gene, required for superinfection immunity, has a sequence similar to that of arabidopsis thaliana g ... | 1998 | 9457865 |
| contact stimulation of tgl and type iv pili in myxococcus xanthus. | myxococcus xanthus tgl mutants lack social motility and type iv pili but can be transiently stimulated to swarm and to make pili by contacting tgl+ cells. the absence of pili in tgl mutants is shown not to be due to the absence of pilin. the rate of pilus elongation after tgl stimulation is shown to be similar to the rate of pilus elongation in wild-type cells, using a new more rapid assay for stimulation. | 1998 | 9457887 |
| alignment enhances the cell-to-cell transfer of pilus phenotype. | social gliding motility of myxococcus xanthus requires polar type iv pili. tgl mutants lack pili and lack social motility. however, both defects can be rescued phenotypically, but not genotypically, when tgl+ donor and tgl- recipient cells make physical contact with each other. what is the cellular and molecular basis of this transfer of phenotype, which is called stimulation? stimulation does not occur in liquid nor in soft (0.5%) agar; however, on a more firm surface (1.0% agar) cells stimulat ... | 1998 | 9501214 |
| the guanosine nucleotide (p)ppgpp initiates development and a-factor production in myxococcus xanthus. | guanosine 3'-di-5'-(tri)di-phosphate nucleotides [(p)ppgpp], synthesized in response to amino acid limitation, induce early gene expression leading to multicellular fruiting body formation in myxococcus xanthus. a mutant (dk527) that fails to accumulate (p)ppgpp in response to starvation was found to be blocked in development prior to aggregation. by use of a series of developmentally regulated tn5lac transcriptional fusion reporters, the time of developmental arrest in dk527 was narrowed to wit ... | 1998 | 9531539 |
| identification of the omega4400 regulatory region, a developmental promoter of myxococcus xanthus. | omega4400 is the site of a tn5 lac insertion in the myxococcus xanthus genome that fuses lacz expression to a developmentally regulated promoter. cell-cell interactions that occur during development, including c signaling, are required for normal expression of tn5 lac omega4400. the dna upstream of the omega4400 insertion has been cloned, the promoter has been localized, and a partial open reading frame has been identified. from the deduced amino acid sequence of the partial open reading frame, ... | 1998 | 9555878 |
| identification of an fad superfamily containing protoporphyrinogen oxidases, monoamine oxidases, and phytoene desaturase. expression and characterization of phytoene desaturase of myxococcus xanthus. | a large number of fad-containing proteins have previously been shown to contain a signature sequence that is referred to as the dinucleotide binding motif. protoporphyrinogen oxidase (ppo), the penultimate enzyme of the heme biosynthetic pathway, is an fad-containing protein that catalyzes the six electron oxidation of protoporphyrinogen ix. sequence analysis demonstrates the presence of the dinucleotide binding motif at the amino-terminal end of the protein. analysis of the current data base re ... | 1998 | 9593705 |
| bacterial motility: secretory secrets of gliding bacteria. | many bacteria glide over surfaces without the aid of flagella. gliding is still somewhat mysterious, but recent studies show that it involves specialized secretory systems that assemble membrane-associated filaments, and the recognition of extracellular components that trigger movement via transmembrane transducers. | 1998 | 9637910 |
| molecular analysis of the dna gyrb gene from myxococcus xanthus. | dna gyrase, an essential type ii topoisomerase, mediates negative supercoiling of the bacterial chromosome, thereby affecting the processes of dna replication, transcription, recombination and repair. the gyrb gene from the gram-negative soil bacterium myxococcus xanthus was sequenced. the sequence predicts a protein of 815 amino acid residues displaying significant homology to all known gyrb proteins. a 6-his-gyrb fusion protein was overexpressed in escherichia coli and purified to near homogen ... | 1998 | 9639935 |
| the extracytoplasmic function sigma factors: role and regulation. | alternative sigma factors provide a means of regulating gene expression in response to various extracellular changes. one such class of sigma factors appears to control a variety of functions, including expression of heat-shock genes in escherichia coli, biosynthesis of alginates and carotenoids in pseudomonas aeruginosa and myxococcus xanthus, respectively, iron uptake in e. coli and pseudomonas spp., nickel and cobalt efflux in alcaligenes europhus, plant pathogenicity in pseudomonas syringae ... | 1998 | 9680198 |
| propionyl-coa carboxylase of myxococcus xanthus: catalytic properties and function in developing cells. | an acyl-coenzyme a carboxylase that carboxylates acetyl-coa, butyryl-coa, propionyl-coa, and succinyl-coa was purified from myxococcus xanthus. since the enzyme showed maximal rates of carboxylation with propionyl-coa, the enzyme is thought to be propionyl-coa carboxylase. the apparent km values for acetyl-coa, butyryl-coa, propionyl-coa, and succinyl-coa were found to be 0.2, 0. 2, 0.03, and 1.0 mm, respectively. the native enzyme has a molecular mass of 605-615 kda and is composed of nonidenti ... | 1998 | 9683657 |
| mgla and mglb are required for the intramacrophage growth of francisella novicida. | francisella novicida is a facultative intracellular pathogen capable of growing in macrophages. a spontaneous mutant of f. novicida defective for growth in macrophages was isolated on lb media containing the chromogenic phosphatase substrate 5-bromo-4-chloro-3-indolyl phosphate (x-p) and designated gb2. using an in cis complementation strategy, four strains were isolated that are restored for growth in macrophages. a locus isolated from one of these strains complements gb2 for both the intracell ... | 1998 | 9701818 |
| pilt mutations lead to simultaneous defects in competence for natural transformation and twitching motility in piliated neisseria gonorrhoeae. | neisseria gonorrhoeae, the gram-negative aetiological agent of gonorrhoeae, is one of many mucosal pathogens of man that expresses competence for natural transformation. expression of this phenotype by gonococci appears to rely on the expression of type iv pili (tfp), but the mechanistic basis for this relationship remains unknown. during studies of gonococcal pilus biogenesis, a homologue of the pilt family of proteins, required for tfp-dependent twitching motility in pseudomonas aeruginosa and ... | 1998 | 9701824 |
| sdek is required for early fruiting body development in myxococcus xanthus. | myxococcus xanthus cells carrying the omega4408 tn5lac insertion at the sde locus show defects in fruiting body development and sporulation. our analysis of sde expression patterns showed that this locus is induced early in the developmental program (0 to 2 h) and that expression increases approximately fivefold after 12 h of development. further studies showed that expression of sde is induced as growing cells enter stationary phase, suggesting that activation of the sde locus is not limited to ... | 1998 | 9721305 |
| a new sigma factor, sigd, essential for stationary phase is also required for multicellular differentiation in myxococcus xanthus. | myxococcus xanthus is a gram-negative bacterium that undergoes spectacular development to form multicellular fruiting bodies under nutrient deprivation. inside a fruiting body, vegetative cells differentiate into spores. a number of sigma factors have been shown to play roles in the regulation of gene expression in the m. xanthus life cycle. additional sigma factors were searched to further explore the m. xanthus life cycle. | 1998 | 9734783 |
| myxococcus xanthus spore coat protein s, a stress-induced member of the betagamma-crystallin superfamily, gains stability from binding of calcium ions. | protein s, a calcium-binding spore coat protein from the soil bacterium myxococcus xanthus, belongs to a group of structurally related proteins, the betagamma-crystallin superfamily. common features of this protein family are the greek-key structural motif or crystallin fold, and the fact that all members are extremely stable long term. to investigate the correlation between the stability and greek-key topology, protein s was cloned, expressed in escherichia coli and purified to homogeneity. ca2 ... | 1998 | 9738899 |
| growth medium-dependent regulation of myxococcus xanthus fatty acid content is controlled by the esg locus. | we compared the cellular fatty acid profiles of myxococcus xanthus cells grown in either a casitone-based complex medium or a chemically defined medium. the cells grown in the complex medium had a much higher content of the abundant branched-chain fatty acid iso-15:0 and several other branched-chain species. the higher branched-chain fatty acid content of the cells grown in the complex medium was dependent on the esg locus, which encodes the e1alpha and e1beta components of a branched-chain keto ... | 1998 | 9748468 |
| chemotaxis in a gliding bacterium. | myxococcus xanthus cells exhibit directed motility up phosphatidylethanolamine (pe) gradients, and we suggest that pe behaves as a chemoattractant. computer-assisted stop-motion digital microscopy was used to record cell movements in slide culture. pe decreased cellular reversal frequency with molecular specificity that was correlated with the fatty acid composition. synthetic dilauroyl (di c12:0) pe and dioleoyl (di c18:1 omega9c) pe suppressed direction reversals and stimulated movement up the ... | 1998 | 9751772 |
| a chaperone in the hsp70 family controls production of extracellular fibrils in myxococcus xanthus. | three independent tn5-lac insertions in the s1 locus of myxococcus xanthus inactivate the sglk gene, which is nonessential for growth but required for social motility and multicellular development. the sequence of sglk reveals that it encodes a homologue of the chaperone hsp70 (dnak). the sglk gene is cotranscribed with the upstream grps gene, which encodes a grpe homologue. unlike sglk, grps is not required for social motility or development. wild-type m. xanthus is encased in extracellular pol ... | 1998 | 9765567 |
| regulation of the expression of a gene encoding beta-endoglucanase secreted by myxococcus xanthus during growth: role of genes involved in developmental regulation. | an endoglucanase, cela, is secreted by myxococcus xanthus only during exponential growth. the production of this enzyme is decreased by mutations in 5 different genes (exc +/- phenotype), three of which correspond to asg genes which regulate the production of an early cell-to-cell signal in development. transcription of cela is decreased in two of these exc +/- mutants, whereas a post-transcriptional step is affected in two other exc- mutants. thus, asg genes, in addition to regulating the onset ... | 1998 | 9766232 |
| crl stimulates rpos activity during stationary phase. | rpos, an alternative primary sigma factor, has been shown to be regulated at multiple levels, including transcription, translation and protein stability. here, we present evidence that suggests that rpos is regulated at yet another level by the product of the crl gene. the crl gene was first thought to encode the major curlin subunit of curli (curli are surface structures that are induced by growth into stationary phase under conditions of low osmolarity and low temperature). later, it was deter ... | 1998 | 9767590 |
| the pilh gene encodes an abc transporter homologue required for type iv pilus biogenesis and social gliding motility in myxococcus xanthus. | type iv pilus genes have been shown to be required for social gliding motility in myxococcus xanthus. we report the discovery of four additional pil genes: pild, a homologue of type iv prepilin leader peptidases; and pilg, pilh and pili, which have no known homologues in other type iv pilus systems. pilh encodes an atp-binding cassette (abc) transporter homologue, the first such homologue to be required for the biogenesis of any bacterial pilus type. pilg and pili are co-transcribed with pilh an ... | 1998 | 9767592 |
| loss of social behaviors by myxococcus xanthus during evolution in an unstructured habitat. | social behaviors are often targets of natural selection among higher organisms, but quantifying the effects of such selection is difficult. we have used the bacterium myxococcus xanthus as a model system for studying the evolution of social interactions. changes in the social behaviors of 12 m. xanthus populations were quantified after 1,000 generations of evolution in a liquid habitat, in which interactions among individuals were continually hindered by shaking and low cell densities. derived l ... | 1998 | 9770494 |
| purification of and kinetic studies on a cloned protoporphyrinogen oxidase from the aerobic bacterium bacillus subtilis. | the previously cloned and expressed protoporphyrinogen oxidase from bacillus subtilis has been purified to homogeneity by ni2+ affinity chromatography using a his6 tag and characterized. the enzyme has a molecular weight of approximately 56,000 daltons, a pi of 7.5, a ph optimum (protoporphyrinogen) of 8.7, and a noncovalently bound flavine adenine dinucleotide cofactor. the michaelis constants (km) for protoporphyrinogen-ix, coproporphyrinogen-iii, and mesoporphyrinogen-ix are 1.0, 5.29, and 4. ... | 1998 | 9784236 |
| protein w, a spore-specific protein in myxococcus xanthus, formation of a large electron-dense particle in a spore. | the gene for the major spore-specific protein, termed protein w, was cloned, and it was found that protein w is composed of 426 amino acid residues including 31% charged (133 residues) and 39% hydrophobic (166 residues) amino acids. in the protein, a motif consisting of five amino acid residues [(v/l/i)-r-e-r-(v/l/i)] is repeated 28 times, and another motif [m-m-(p/g)-q-g] five times. protein w is synthesized during a very late stage of development, forming a single, large electron-dense particl ... | 1998 | 9786185 |
| regulation of motility behavior in myxococcus xanthus may require an extracytoplasmic-function sigma factor. | using interaction trap technology, we identified a putative extracytoplasmic-function (ecf) sigma factor (rpoe1) in myxococcus xanthus, a bacterium which has a complex life cycle that includes fruiting body formation. the first domain of the response regulator protein frzz, a component of the frz signal transduction system, was used as bait. although the rpoe1 protein displayed no interactions with control proteins presented as bait, a weak interaction with a second m. xanthus response regulator ... | 1998 | 9791117 |
| an abc transporter plays a developmental aggregation role in myxococcus xanthus. | myxococcus xanthus is a gram-negative bacterium which has a complex life cycle. autochemotaxis, a process whereby cells release a self-generated signaling molecule, may be the principal mechanism facilitating directed motility in both the vegetative swarming and developmental aggregation stages of this life cycle. the process requires the frz signal transduction system, including frzz, a protein which is composed of two domains, both showing homology to the enteric chemotaxis response regulator ... | 1998 | 9791121 |
| methylation of frzcd defines a discrete step in the developmental program of myxococcus xanthus. | myxococcus xanthus is a gram-negative soil bacterium which undergoes fruiting body formation during starvation. the frz signal transduction system has been found to play an important role in this process. frzcd, a methyl-accepting taxis protein homologue, shows modulated methylation during cellular aggregation, which is thought to be part of an adaptation response to an aggregation signal. in this study, we assayed frzcd methylation in many known and newly isolated mutants defective in fruiting ... | 1998 | 9791131 |
| the myxococcus xanthus lipopolysaccharide o-antigen is required for social motility and multicellular development. | the gliding bacterium myxococcus xanthus aggregates to form spore-filled fruiting bodies when nutrients are limiting. defective fruiting-body formation and sporulation result from mutations in the sasa locus, which encodes the wzm wzt wbga (formerly rfbabc) lipopolysaccharide (lps) o-antigen biosynthesis genes. mutants carrying these same sasa mutations are defective in social motility and form small glossy colonies. we report here that the developmental and motility phenotypes of four mutants e ... | 1998 | 9791173 |
| targeted mutagenesis of sigma54 activator proteins in myxococcus xanthus. | myxococcus xanthus dna segments related to the highly conserved central sequence of sigma54 activator proteins have been investigated. a genetic technique designed to inactivate a gene that encodes such an activator by inserting a plasmid-borne internal fragment of the putative gene has been tested. when the internal fragment inserted by homologous recombination into the corresponding chromosomal locus, the expected duplication of the gene was observed by southern hybridization. the single restr ... | 1998 | 9811647 |
| kinetic stabilisation of a modular protein by domain interactions. | protein s, a two-domain spore coat protein from myxococcus xanthus, is structurally related to eye-lens pr crystallins. no natural monomeric one-domain member of this protein superfamily is known. to determine the stability of the single domains and to explain the ubiquitous domain duplication, the isolated domains of protein s were constructed. the n-domain is thermodynamically more stable than the c-domain. in intact protein s, domain interactions lead to an apparent decrease in stability of t ... | 1998 | 9821973 |
| myxococcus xanthus sasn encodes a regulator that prevents developmental gene expression during growth. | myxococcus xanthus multicellular fruiting body development is initiated by nutrient limitation at high cell density. five clustered point mutations (sasb5, -14, -15, -16, and -17) can bypass the starvation and high-cell-density requirements for expression of the 4521 developmental reporter gene. these mutants express 4521 at high levels during growth and development in an asgb background, which is defective in generation of the cell density signal, a signal. a 1.3-kb region of the sasb locus clo ... | 1998 | 9829930 |
| identification and characterization of the myxococcus xanthus arge gene. | the chromosomal acetylornithine deacetylase (arge) gene of myxococcus xanthus was identified via homology to acetylornithine deacetylases from other bacterial species. a mutant carrying a disruption in arge was unable to grow on minimal media lacking supplemental arginine and formed fruiting bodies and spores in response to arginine starvation at high cell density. | 1998 | 9829957 |
| the strategy of myxococcus xanthus for group cooperative behavior. | new evidence has been presented from our laboratory that the gliding bacterium, myxococcus xanthus, does not home by chemotaxis toward a nutrient source. our experiments, those of others, and the theory presented here combine to suggest a model, called the 'pied piper' model. it hypothesizes a gene that has a high mutation rate forward and back (say something in excess 10(-4) mutations per cell generation) which leads to switching between two motility states. occasionally rare organisms become g ... | 1998 | 9850416 |
| inhibition of development of myxococcus xanthus by eukaryotic protein kinase inhibitors. | myxococcus xanthus is a social bacterium that lives in the soil and undergoes spectacular development to form multicellular fruiting bodies. it contains a large family of eukaryote-like serine/threonine protein kinases. we found that a number of inhibitors for eukaryotic protein serine, threonine, and tyrosine kinases could inhibit the development and sporulation of m. xanthus to various degrees. these results suggest that serine/threonine and tyrosine phosphorylation may be involved in developm ... | 1998 | 9851997 |
| the aada gene of plasmid r100 confers resistance to spectinomycin and streptomycin in myxococcus xanthus. | plasmids with the aada gene from plasmid r100, which confers resistance to the aminoglycosides spectinomycin and streptomycin in escherchia coli, can be introduced into wild-type myxococcus xanthus, strain dk1622, by electroporation. recombinant m. xanthus strains with integrated plasmids carrying the aada gene acquire resistance to high levels of these antibiotics. selection for aada in m. xanthus can be carried out independently of, or simultaneously with, selection for resistance to kanamycin ... | 1998 | 9852026 |
| why and how bacteria communicate. | 1997 | 9000763 | |
| biochemical characterization of pkn2, a protein ser/thr kinase from myxococcus xanthus, a gram-negative developmental bacterium. | pkn2, a protein ser/thr kinase, from the developmental bacterium myxococcus xanthus was expressed under a t7 promoter in escherichia coli and purified. purified pkn2 retained the autophosphorylation activity with the km value of 177 microm for atp and 73 nmol/min/mg for vmax. the optimum ph and temperature were determined to be 7.5 and 35 degrees c, respectively. the autophosphorylation activity was inhibited by staurosporine with the ic50 value of 400 nm while h-7 and genistein had little effec ... | 1997 | 9001395 |
| the myxococcus xanthus pilt locus is required for social gliding motility although pili are still produced. | social gliding motility in myxococcus xanthus depends on the presence of type iv pili. to begin to examine the role of pili in social motility, 17 mutants were identified which had lost social motility, but still expressed pili. four of these mutants carry point mutations which mapped to a locus upstream of the recently identified pils, pilr, and pila genes. sequencing of this locus revealed a gene with homology to pilt from pseudomonas aeruginosa. sequencing of the four point mutations revealed ... | 1997 | 9004225 |
| characterization of csga, a new member of the forespore-expressed sigmag-regulon from bacillus subtilis. | a new locus, csga, has been identified in a search for developmental genes transcribed by e sigmag in bacillus subtilis. csga has the potential to encode three small proteins, csgaa, csgab and csgac. the latter two would be encoded by overlapping orfs. csga is expressed in the spore chamber of the differentiating cell and is under the control of sigmag and the transcriptional regulatory protein spovt. mutation of csga did not affect spore formation but produced a subtle defect in the ability of ... | 1997 | 9016963 |
| further characterization and in situ localization of chain-like aggregates of the gliding bacteria myxococcus fulvus and myxococcus xanthus. | for the first time, chain-like aggregates, called "strands," have been enriched from crude cell wall preparations of liquid-grown vegetative cells of two strains of myxococcus xanthus. these strands are highly isomorphic to macromolecular structures, previously described for myxococcus fulvus (lünsdorf and reichenbach, j. gen. microbiol. 135:1633-1641, 1989). the strands are morphologically composed of ring elements, consisting of six or more peripheral protein masses and possibly three small ce ... | 1997 | 9023208 |
| adp-ribosylation by the extracellular fibrils of myxococcus xanthus. | the isolated, extracellular fibrils of the myxobacterium, myxococcus xanthus, are capable of carrying out adp-ribosylation. the substrate for the adp-ribosylation is reactive with monoclonal antibody 2105, which has been shown to be directed specifically against the integral fibril proteins. the extracellular fibrils thus contain both the adp-ribosyl transferase and the substrate for the ribosylation. this process may play a role in the contact-mediated cell-cell interactions that are an importa ... | 1997 | 9044257 |
| pkn9, a ser/thr protein kinase involved in the development of myxococcus xanthus. | the myxococcus xanthus gene, pkn9, encodes a protein that contains significant homology with eukaryotic ser/thr protein kinases. the pkn9 gene was singled out of a previously identified family of kinase genes by amplification techniques that displayed differences in kinase gene expression during selected periods of the m. xanthus life cycle. pkn9 was constitutively expressed during vegetative growth and upregulated during the aggregation stage of early development. it consists of 589 amino acids ... | 1997 | 9044280 |
| sigma54, a vital protein for myxococcus xanthus. | the rpon gene encoding the transcription factor sigma54 in myxococcus xanthus has been cloned using a heterologous rpon probe. the sequence of the cross-hybridizing dna confirmed the existence of an orf 1518 bp long that encodes a well conserved member of the sigma54 family of sigma factors. low- as well as high-stringency hybridizations detected only a single rpon gene in the m. xanthus chromosome. in other bacteria, sigma54 is an alternative sigma, and null mutants are viable. however, all att ... | 1997 | 9050890 |
| a gene involved in both protein secretion during growth and starvation-induced development encodes a subunit of the nadh:ubiquinone oxidoreductase in myxococcus xanthus. | the secretion of numerous proteins during vegetative growth of myxococcus xanthus, and the multicellular development cycle induced upon starvation of these bacteria, are partially interrelated in so far as mutants impaired in extracellular protein production are unable to undergo development. we have cloned and sequenced a gene in which a tn5 insertion leads to a decrease in the production of most, if not all, extracellular proteins, and prevents development and sporulation. the deduced protein ... | 1997 | 9076740 |
| identification and characterization of myxococcus xanthus mutants deficient in calcofluor white binding. | calcofluor white is a fluorescent dye that binds to glycans and can be used to detect extracellular polysaccharide in myxococcus xanthus and many other bacteria. we observed that an esg mutant showed less binding to calcofluor white than wild-type cells. unlike s-motility mutants that share this phenotypic characteristic, the esg mutant exhibited s motility. this led us to identify a collection of nine new transposon insertion mutants, designated cds (for calcofluor white binding deficient and s ... | 1997 | 9139901 |
| starvation-independent sporulation in myxococcus xanthus involves the pathway for beta-lactamase induction and provides a mechanism for competitive cell survival. | myxococcus xanthus is a gram-negative, soil-dwelling bacterium with a complex life cycle which includes fruiting body formation and sporulation in response to starvation. this developmental process is slow, requiring a minimum of 24-48 h, and requires cells to be at high cell density on a solid surface. it is known that, in the absence of starvation, vegetatively growing cell suspensions can form 'glycerol spores' when exposed to high levels of glycerol, usually 0.5 m. the cells differentiate fr ... | 1997 | 9194710 |
| temperate myxococcus xanthus phage mx8 encodes a dna adenine methylase, mox. | temperate bacteriophage mx8 of myxococcus xanthus encapsidates terminally repetitious dna, packaged as circular permutations of its 49-kbp genome. during both lytic and lysogenic development, mx8 expresses a nonessential dna methylase, mox, which modifies adenine residues in occurrences of xhoi and psti recognition sites, ctcgag and ctgcag, respectively, on both phage dna and the host chromosome. the mox gene is necessary for methylase activity in vivo, because an amber mutation in the mox gene ... | 1997 | 9209041 |
| the tgl gene: social motility and stimulation in myxococcus xanthus. | mutations in the tgl locus inactivate social gliding motility in myxococcus xanthus and block production of pili. the tgl locus is distinctive among the genes for social motility because social gliding and pili can be restored transiently to tgl mutant cells by mixing them with tgl+ cells, a process known as stimulation. the tgl locus was cloned with a linked insertion of transposon tn5 by using the kanamycin resistance encoded by that transposon. a 16-kb segment of chromosomal dna complemented ... | 1997 | 9209055 |
| identification and localization of the tgl protein, which is required for myxococcus xanthus social motility. | tgl protein is required for the production of the type iv pili found at a pole of the myxococcus xanthus cell. these pili are essential for social motility. evidence is presented that tgl is a membrane protein, based on experiments with polyclonal antibody specific for tgl that was raised against the fusion proteins beta-galactosidase-tgl and trpe-tgl. immunoaffiity-purified antibody reacted with a protein in m. xanthus having an apparent molecular mass of 27.5 kda as measured by sodium dodecyl ... | 1997 | 9209056 |
| regulation of directed motility in myxococcus xanthus. | myxococcus xanthus is a gram-negative bacterium that exhibits a complex life cycle. during vegetative growth, cells move as large swarms. however, when starved, cells aggregate into fruiting bodies and sporulate. both vegetative swarming and developmental aggregation require gliding motility, which involves the slow movement of cells on a solid surface in the absence of flagella. the frequency of cell reversals controls the direction of movement and is regulated by the frz genes, which encode th ... | 1997 | 9219997 |
| molecular genetic analysis of type-4 pilus biogenesis and twitching motility using pseudomonas aeruginosa as a model system--a review. | genetic analysis of pseudomonas aeruginosa pilus biogenesis and twitching motility has revealed the requirement for several pil loci which have been localized to different regions of the chromosome. one pil locus, designated pile, resides at approx. 71 min on the pao genetic map, a region of the chromosome previously shown to harbor a number of genes required for pilus assembly (i.e., pila, -b, -c, -d, -r and -s). the pile protein shows significant sequence identity to the n-terminal domain of p ... | 1997 | 9224880 |
| complementation of sporulation and motility defects in a prokaryote by a eukaryotic gtpase. | the complex prokaryote, myxococcus xanthus, undergoes a program of multicellular development when starved for nutrients, culminating in sporulation. m. xanthus makes mgla, a 22-kda, soluble protein that is required for both multicellular development and gliding motility. mgla is similar in sequence to the saccharomyces cerevisiae sar1 protein, a member of the ras/rab/rho superfamily of small eukaryotic gtpases. the sar1 gene, when integrated into the m. xanthus genome, complements the sporulatio ... | 1997 | 9275220 |
| a crtb homolog essential for photochromogenicity in mycobacterium marinum: isolation, characterization, and gene disruption via homologous recombination. | a gene essential for light-induced pigment production was isolated from the photochromogen mycobacterium marinum by heterologous complementation of an m. marinum cosmid library in the nonchromogen mycobacterium smegmatis. this gene is part of an operon and homologous to the streptomyces griseus and myxococcus xanthus crtb genes encoding phytoene synthase. gene replacement at this locus was achieved via homologous recombination, demonstrating that its expression is essential for photochromogenici ... | 1997 | 9294446 |
| in vitro transcription of myxococcus xanthus genes with rna polymerase containing sigmaa, the major sigma factor in growing cells. | myxococcus xanthus is a gram-negative bacterium that undergoes multicellular development upon starvation. we have developed a simple and rapid procedure for partial purification of rna polymerase from growing m. xanthus cells, using heparin-agarose and dna-cellulose chromatographies. in addition to core subunits, the enzyme contains one fairly abundant polypeptide of approximately 105 kda. we have shown by western blot analysis and protein sequencing that the 105-kda polypeptide is sigmaa, the p ... | 1997 | 9302009 |
| picture story. an eye on crystallins. | 1997 | 9302991 | |
| sequence of the bacillus subtilis genome region in the vicinity of the lev operon reveals two new extracytoplasmic function rna polymerase sigma factors sigv and sigz. | two regions with sizes 18,900 and 25,400 bp, which join previously known contigs containing levrdefg, aadk and blt genes near 235 degrees of the bacillus subtilis chromosome, were sequenced. among others, two genes, which encode proteins homologous to rna polymerase sigma-factors, were identified within this region. the gene products designated sigv and sigz, show the highest homology with sigma-factors encoded by the gene carq of myxococcus xanthus and sigx (formerly orfx20) of b. subtilis, cor ... | 1997 | 9308178 |
| trans-acting regulation of antibiotic ta genes in myxococcus xanthus. | two regulatory mutations of myxococcus xanthus, which cause an increase in the transcription of genes required for antibiotic ta synthesis, were mapped by transduction and their effect on transcription of four ta genes examined. the two regulatory mutations were closely linked and located within the 40-kb ta gene cluster on the m. xanthus chromosome. recombinants were constructed which contained one of the regulatory mutations and promoter probes in the four different ta genes. both regulatory m ... | 1997 | 9351195 |
| cloning and sequencing of two genes, prta and prtb, from myxococcus xanthus, encoding prta and prtb proteases, both of which are required for the protease activity. | the sequence of a 1955-bp taqi dna fragment from myxococcus xanthus was determined. this fragment contains two complete genes, designated prta and prtb. the prta and prtb orfs extend over 828 and 798 bp, respectively. they are separated only by 3 nt and appear to be present in a polycistronic transcriptional unit. a typical lipoprotein signal sequence is present at the n terminus of the two deduced polypeptides. the aa sequence of prta shows a high degree of identity to the region adjacent to th ... | 1997 | 9370274 |
| propionyl coenzyme a carboxylase is required for development of myxococcus xanthus. | a dcm-1 mutant, obtained by transposon mutagenesis of myxococcus xanthus, could aggregate and form mounds but was unable to sporulate under nutrient starvation. a sequence analysis of the site of insertion of the transposon showed that the insertion lies within the 3' end of a 1,572-bp open reading frame (orf) designated the m. xanthus pccb orf. the wild-type form of the m. xanthus pccb gene, obtained from a lambdaembl library of m. xanthus, shows extensive similarity to a beta subunit of propio ... | 1997 | 9371458 |
| comparative heavy metal biosorption study of brewery yeast and myxococcus xanthus biomass. | the biosorption for la2+, co2+, mn2+, uo2(2+), pb2+, ag+, zn2+, cd2+ and cr2+ by wet and dry biomass form myxococcus xanthus obtained from laboratory cultures and saccharomyces cerevisiae from the brewing industry has been studied. m. xanthus biomass was found to be the most efficient biosorbent for all of the metals assayed. however, due to the fact that s. cerevisiae is a low cost residual by-product from the brewing industry, and at the same time yields good levels of biosorption, it is consi ... | 1997 | 9375355 |
| rapid purification and characterization of nucleoside diphosphate kinase isoforms using atp-sepharose affinity column chromatography. | nucleoside diphosphate kinases (ndp kinases), products of the nm23 gene, catalyze the transfer of the terminal phosphate group of the nucleoside triphosphate to the corresponding diphosphate and may be involved in tumor metastasis suppression, development, and signal transduction. ndp kinase from various sources including human erythrocytes, rat brain tissue and e. coli strain bl21 transformed with pet3c expression plasmids containing nm23-h1 or nm23-h2, were purified in one step to homogeneity ... | 1997 | 9387150 |
| a regulatory locus, pehsr, controls polygalacturonase production and other virulence functions in ralstonia solanacearum. | we previously identified a locus that regulates production of polygalacturonase (pg), an extracellular plant cell wall-degrading enzyme important in bacterial wilt of plants caused by ralstonia (pseudomonas) solanacearum. the dna sequence of this locus, called pehsr, was determined and two consecutive open reading frames (orfs) of 1,905 and 1,680 bp were identified. the amino acid sequences predicted to be encoded by these orfs are similar to those of regulators of pilin synthesis in pseudomonas ... | 1997 | 9390420 |
| regulation of expression of the pila gene in myxococcus xanthus. | type iv pili are required for social gliding motility in myxococcus xanthus. in this work, the expression of pilin (the pila gene product) during vegetative growth and fruiting-body development was examined. a polyclonal antibody against the pila gene product (prepilin) was prepared, along with a pila-lacz fusion, and was used to assay expression of pila in m. xanthus in different mutant backgrounds. pila expression required the response regulator pilr but was negatively regulated by the putativ ... | 1997 | 9401034 |
| myxococcus xanthus sass encodes a sensor histidine kinase required for early developmental gene expression. | initiation of myxococcus xanthus multicellular development requires integration of information concerning the cells' nutrient status and density. a gain-of-function mutation, sasb7, that bypasses both the starvation and high cell density requirements for developmental expression of the 4521 reporter gene, maps to the sass gene. the wild-type sass gene was cloned and sequenced. this gene is predicted to encode a sensor histidine protein kinase that appears to be a key element in the transduction ... | 1997 | 9401035 |
| a mutation that affects fibril protein, development, cohesion and gene expression in myxococcus xanthus. | extracellular matrix fibrils are involved in the cell-cell interactions of the social prokaryote, myxococcus xanthus. the fibrils are composed of a carbohydrate backbone and a set of five integral fibrillar proteins (ifps) ranging from 14 to 66 kda. as part of an attempt to understand the function(s) of the ifps, a mutant (ifp-1:20) was generated that lacks ifp-1:20, one of the fibril proteins, as shown by western blot analysis of both whole cells and isolated fibrils. unlike those of the parent ... | 1997 | 9421894 |
| secretion kinetics of endo-n-acetyl-beta-d-glucosaminidase during vegetative growth of myxococcus xanthus. | it was recently demonstrated that endo-n-acetyl-beta-d-glucosaminidases (engase) acting on n-glycosylproteins are produced by myxobacteria. in this study, it was shown that the secretion of engase during vegetative growth of myxococcus xanthus was cell-density-dependent. the activity produced per cell increased up to 6 x 10(8) cells/ml and stabilized thereafter (maximum level). two of the developmental mutants used in this study (bsga and csga) were locked for engase secretion into the maximum l ... | 1996 | 8763609 |
| integration of bacteriophage mx8 into the myxococcus xanthus chromosome causes a structural alteration at the c-terminal region of the intp protein. | mx8 is a generalized transducing phage that infects myxococcus xanthus cells. this phage is lysogenized in m. xanthus cells by the integration of its dna into the host chromosome through site-specific recombination. here, we characterize the mechanism of mx8 integration into the m. xanthus chromosome. the mx8 attachment site, attp, the m. xanthus chromosome attachment site, attb, and two phage-host junctions, attl and attr, were cloned and sequenced. sequence alignments of attp, attb, attl, and ... | 1996 | 8763924 |
| tyrosine phosphorylation in myxococcus xanthus, a multicellular prokaryote. | tyrosine phosphorylation is an extremely rare event in prokaryotes, occurring almost exclusively in multicellular eukaryotes. we have identified, for the first time, by the use of antiphosphotyrosine monoclonal antibody and western blot (immunoblot) analysis, two tyrosine-phosphorylated membrane proteins in the multicellular prokaryote myxococcus xanthus. the pattern of tyrosine phosphorylation was shown to change during development, indicating a possible role for this regulatory modification du ... | 1996 | 8763935 |
| light-induced carotenogenesis in myxococcus xanthus: light-dependent membrane sequestration of ecf sigma factor carq by anti-sigma factor carr. | light-induced carotenogenesis in myxococcus xanthus is under the control of the carqrs operon. carq, a proposed extracytoplasmic (ecf) rna polymerase sigma factor, is required for expression of the operon and the carc gene that encodes phytoene dehydrogenase. carr, an inner membrane protein in escherichia coli, is essential for carqrs promoter inactivation in the dark. cars is required for the light-dependent expression of the promoter of the carb gene cluster that encodes the rest of the struct ... | 1996 | 8821946 |
| propagation of traveling waves in excitable media. | 1996 | 8824584 | |
| markerless deletions of pil genes in myxococcus xanthus generated by counterselection with the bacillus subtilis sacb gene. | in-frame deletions of pila and pils were constructed in myxococcus xanthus with a plasmid integration-excision strategy facilitated by sacb. sacb conferred sucrose sensitivity upon its m. xanthus host only when it lay in the same orientation as adjacent m. xanthus genes. gene orientation also affected the efficiency of sucrose counterselection in the sucrose-sensitive strains. the deltapila mutant lacked pili and social motility, while the deltapils mutant showed no defect in either phenotype. | 1996 | 8824635 |
| defect in export and synthesis of the periplasmic galactose receptor mglb in dnak mutants of escherichia coli, and decreased stability of the mglb mrna. | the high-affinity galactose permease, which comprises the periplasmic galactose receptor mglb, the membrane translocator mglc and the membrane-associated atpase mgla, displayed a reduced activity in a dnak temperature-sensitive mutant of escherichia coli. this reduced transport activity correlated with a reduction in the quantity of mglb. at 42 degrees c, an accumulation of pre-mglb in the dnak temperature-sensitive mutant reflected a defect in mglb export. in addition, an accumulation of pre-mg ... | 1996 | 8828228 |
| sequence and analysis of a 33 kb fragment from the right arm of chromosome xv of the yeast saccharomyces cerevisiae. | we have determined the nucleotide sequence of a cosmid (peoa423) from chromosome xv of saccharomyces cerevisiae. analysis of the 33,173 bp sequence reveals the presence of 20 putative open reading frames (orfs). five of them correspond to previously known genes (mgm1, ste4, cdc44, ste13, rpb8). the previously published nucleotide sequences are in perfect agreement with our sequence except for ste4 and mgm1. in the latter case, 59 amino acids were truncated from the published protein at its n-ter ... | 1996 | 8840505 |
| bacterial signalling involving eukaryotic-type protein kinases. | protein ser, thr and tyr kinases play essential roles in signal transduction in organisms ranging from yeast to mammals, where they regulate a variety of cellular activities. during the last few years, a number of genes that encode eukaryotic-type protein kinases have also been identified in four different bacterial species, suggesting that such enzymes are also widespread in prokaryotes. although many of them have yet to be fully characterized, several studies indicate that eukaryotic-type prot ... | 1996 | 8861199 |
| a mgl-like operon in treponema pallidum, the syphilis spirochete. | a 38-kda lipoprotein of treponema pallidum subsp. pallidum (t. pallidum), the syphilis spirochete, previously was identified as a putative homolog of e. coli mglb [becker et al. (1994) infect. immun. 62, 1381-1391]. in the present study, genome walking in regions adjacent to the t. pallidum 38-kda lipoprotein gene has identified three contiguous genes (tp-mglb [formerly tpp38], tp-mgla, and tp-mglc) which appear to comprise a mgl-like operon in t. pallidum. a prominent transcript corresponding t ... | 1996 | 8921855 |
| the myxococcus xanthus developmentally expressed asgb-dependent genes can be targets of the a signal-generating or a signal-responding pathway. | functional myxococcus xanthus a signal-generating and a signal-responding pathways are required for the progression through early multicellular development. to identify genes responsive to these pathways, the expression of eight early developmental genes was analyzed. this examination identified one gene as a target of the a signal-generating pathway and four genes as targets of the a signal-responding pathway. | 1996 | 8932321 |
| effects of overexpression of pkn2, a transmembrane protein serine/threonine kinase, on development of myxococcus xanthus. | pkn2 is a putative transmembrane protein serine/threonine kinase required for normal development of myxococcus xanthus. the effect of pkn2 overexpression on development of m. xanthus was examined by expressing pkn2 under the control of a kanamycin promoter. pkn2 was clearly detected by western blot (immunoblot) analysis in the overexpression strain (the pkm/pkn2 strain) but could not be detected in the wild-type strain. overexpressed pkn2 was located almost exclusively in the membrane fraction, ... | 1996 | 8932326 |
| two multifunctional peptide synthetases and an o-methyltransferase are involved in the biosynthesis of the dna-binding antibiotic and antitumour agent saframycin mx1 from myxococcus xanthus. | saframycin mx1 is a dna-binding antibiotic and antitumour agent produced by myxococcus xanthus. it is a heterocyclic quinone, thought to be synthesized via the linear peptide intermediate alaglytyrtyr. analysis of 14.1 kb dna sequence involved in saframycin production revealed genes for two large multifunctional peptide synthetases of 1770 and 2605 amino acids, respectively, and a putative o-methyltransferase of 220 amino acids. the three orfs read in the same direction and are separated by shor ... | 1996 | 8936303 |
| frua, a putative transcription factor essential for the development of myxococcus xanthus. | a new developmental gene, frua, of myxococcus xanthus was cloned using a one-step cloning vector, tnv. dna sequencing of the wild-type allele of the frua gene indicated that the frua gene encodes a protein of 229 amino acid residues with a calculated molecular weight of 24672. the deduced amino acid sequence of frua protein showed similarity to those of many bacterial regulatory proteins carrying a dna-binding helix-turn-helix motif. the transcription-initiation site of the frua gene was determi ... | 1996 | 8951822 |
| identification and sequences of the treponema pallidum mgla and mglc genes. | treponema pallidum, the agent of syphilis, cannot be continuously cultivated in vitro. to identify treponemal genes encoding exported proteins, we performed tnphoa mutagenesis of a t. pallidum genomic dna library in escherichia coli. clone 6d2 was chosen for further study based on partial nucleotide sequence obtained from p6d2 containing a tnphoa insertion. a complete open reading frame (orf1) and a truncated orf (orf2) were identified in the treponemal dna of p6d2. orf1 encodes a hydrophobic pr ... | 1996 | 8988365 |
| positive-negative kg cassettes for construction of multi-gene deletions using a single drug marker. | positive-negative kg cassettes were developed in order to create a number of independent deletion mutations on the bacterial chromosome using a single drug marker. these cassettes consist of a kanamycin-resistant (kmr) gene for positive screening and a galactokinase gene (galk) for negative screening. both genes are in an operon driven by the native kmr promoter and are flanked by identical fragments of yeast chromosomal dna approximately one kb in size. an internal region of a cloned target gen ... | 1996 | 8996101 |
| behavioral analysis of single cells of myxococcus xanthus in response to prey cells of escherichia coli. | myxococcus xanthus cells move over surfaces by gliding motility. the frz signal transduction system is used to control the reversal frequency, and thus the overall direction of movement of m. xanthus cells. we analyzed the behavior of wild-type and frz mutant cells in response to prey bacteria (escherichia coli). wild-type cells of m. xanthus did not respond to microcolonies of e. coli until they made physical contact. cells which penetrated a colony remained in the colony until all of the prey ... | 1996 | 8998990 |
| purification and in vitro phosphorylation of myxococcus xanthus asga protein. | the deduced amino acid sequence of the myxococcus xanthus asga protein contains an n-terminal domain that is homologous to the receiver of response regulators and a c-terminal domain that is homologous to the transmitter of histidine protein kinases. we overexpressed affinity-tagged asga in escherichia coli, purified the recombinant protein, and showed that asga has autokinase activity in vitro. the results of chemical-stability assays suggest that asga is phosphorylated on a histidine and provi ... | 1996 | 8550431 |
| mutants of myxococcus xanthus dsp defective in fibril binding. | the dsp mutant of myxococcus xanthus lacks extracellular fibrils and as a result is unable to undergo cohesion, group motility, or development (j. w. arnold and l. j. shimkets, j. bacteriol. 170:5765-5770, 1983; j. w. arnold and l. j. shimkets, j. bacteriol. 170:5771-5777, 1983; r. m. behmlander and m. dworkin, j. bacteriol. 173:7810-7821, 1991; l. j. shimkets, j. bacteriol. 166:837-841, 1986; l. j. shimkets, j. bacteriol. 166:842-848, 1986). however, cohesion and development can be phenotypical ... | 1996 | 8550502 |
| suppression of a signaling defect during myxococcus xanthus development. | the csga gene encodes an extracellular protein that is essential for cell-cell communication (c-signaling) during fruiting body development of myxococcus xanthus. two transposon insertions in the socabc operon, soc-560 and socc559, restore development to csga null mutants. mixing soc-560 csga cells or socc559 csga cells with csga cells at a ratio of 1:1 stimulated the development of csga cells, suggesting that soc mutations allow cells to produce the c-signal or a similar molecule via a csga-ind ... | 1996 | 8576071 |
| intercellular c-signaling in myxococcus xanthus involves a branched signal transduction pathway. | c-factor, the product of the csga gene, is a cell-surface associated short-range intercellular signaling protein in myxococcus xanthus. c-factor is required for at least four responses during starvation-induced fruiting body morphogenesis: rippling, aggregation, sporulation, and full expression of the csga gene, all of which fail in a csga mutant. to analyze the c-factor signaling pathway, eight tn5 lac insertion mutants that began but failed to complete fruiting body aggregation were characteri ... | 1996 | 8598300 |
| c factor, a cell-surface-associated intercellular signaling protein, stimulates the cytoplasmic frz signal transduction system in myxococcus xanthus. | c factor, an intercellular signaling protein, is required for aggregation and sporulation of the social bacterium, myxococcus xanthus. we report that c factor, which normally is associated with the cell surface, provides input to the frz signal transduction cascade. elements of this cascade have sequence homology to bacterial chemotaxis systems and are known to control the frequency of gliding reversal. exposure of developing cells of a c-factor-less mutant (csga) to purified c factor increases ... | 1996 | 8610100 |
| protoporphyrinogen oxidase of myxococcus xanthus. expression, purification, and characterization of the cloned enzyme. | protoporphyrinogen oxidase (ec 1.3.3.4) catalyzes the six electron oxidation of protoporphyrinogen ix to protoporphyrin ix. the enzyme from the bacterium myxococcus xanthus has been cloned, expressed, purified, and characterized. the protein has been expressed in escherichia coli using a tac promoter-driven expression plasmid and purified to apparent homogeneity in a rapid procedure that yields approximately 10 mg of purified protein per liter of culture. based upon the deduced amino acid sequen ... | 1996 | 8621504 |
| the myxococcus xanthus rfbabc operon encodes an atp-binding cassette transporter homolog required for o-antigen biosynthesis and multicellular development. | a wild-type sasa locus is critical for myxococcus xanthus multicellular development. mutations in the sasa locus cause defective fruiting body formation, reduce sporulation, and restore developmental expression of the early a-signal-dependent gene 4521 in the absence of a signal. the wild-type sasa locus has been located on a 14-kb cloned fragment of the m. xanthus chromosome. the nucleotide sequence of a 7-kb region containing the complete sasa locus was determined. three open reading frames en ... | 1996 | 8626291 |
| characterization of the regulatory region of a cell interaction-dependent gene in myxococcus xanthus. | omega 4403 is the site of a tn5 lac insertion in the myxococcus xanthus genome that fuses lacz expression to a developmentally regulated promoter. cell-cell interactions that occur during development, including c-signaling, are required for expression of tn5 lac omega 4403. we have cloned dna upstream of the omega 4403 insertion site, localized the promoter, and identified a potential open reading frame. from the deduced amino acid sequence, the gene disrupted by tn5 lac omega 4403 appears to en ... | 1996 | 8626320 |
| photolyase of myxococcus xanthus, a gram-negative eubacterium, is more similar to photolyases found in archaea and "higher" eukaryotes than to photolyases of other eubacteria. | we report the identification of the gene encoding a dna photolyase (phra) from the gram-negative eubacterium myxococcus xanthus. the deduced amino acid sequence of m. xanthus photolyase indicates that the protein contains 401 amino acids (mr 45,071). by comparison of the amino acid and dna sequences with those of other known photolyases, it has been found that it is more similar to the deduced amino acid sequences of the photolyases of "higher" eukaryotes than to the photolyases of other eubacte ... | 1996 | 8626418 |
| cell density regulates cellular reversal frequency in myxococcus xanthus. | myxococcus xanthus is a gram-negative bacterium that aggregates to form fruiting bodies when nutrients are limiting. previous studies showed that the frz mutants that are defective in chemotaxis exhibited irregular and infrequent patterns of cellular reversal. in contrast, wild-type cells, when examined individually, reverse relatively frequently, about once every 6 min. it is not known how the change of reversal frequency effects cellular aggregation during fruiting body formation in m. xanthus ... | 1996 | 8633030 |
| a method for the selective isolation of myxococcus directly from soil. | a new method is described for the selective isolation of species of myxococcus directly from soil by dilution plating. the method involves suppression of competing microorganisms with antibiotics combined with air drying and wet heat treatment of soils. fungi were eliminated by supplementing the plating medium with cycloheximide and nystatin. non-sporulating bacteria were controlled by air drying soils and then heating aqueous soil dilutions for 10 min at 56 degrees c. the predominant sporulatin ... | 1996 | 8652116 |
| gliding motility in slide cultures of myxococcus xanthus in stable and steep chemical gradients. | a method was devised to construct stable and steep chemical gradients in slide cultures to study the movements of gliding cells. the movement of myxococcus xanthus individual cells and small swarms was studied in these gradients. there was no response to gradients of casitone and yeast extract that were previously reported to stimulate a positive chemotactic response with m. xanthus. | 1996 | 8655544 |
| molecular cloning and characterization of ddcad-1, a ca2+-dependent cell-cell adhesion molecule, in dictyostelium discoideum. | dictyostelium discoideum expresses edta-sensitive cell-cell adhesion sites soon after the initiation of development, and a ca2+-binding protein of mr 24,000 (designated ddcad-1) has been implicated in this type of adhesiveness. we have previously purified ddcad-1 to homogeneity and characterized its cell binding activity (brar, s. k., and siu, c.-h. (1993) j. biol. chem. 268, 24902-24909). in this report, we describe the cloning of ddcad-1 cdnas. dna sequencing revealed a single open reading fra ... | 1996 | 8663243 |
| a r59w mutation in human protoporphyrinogen oxidase results in decreased enzyme activity and is prevalent in south africans with variegate porphyria. | variegate porphyria (vp), a low-penetrant autosomal dominant inherited disorder of haem metabolism, is characterised by photosensitivity (fig. 1) and a propensity to develop acute neuropsychiatric attacks with abdominal pain, vomiting, constipation, tachycardia, hypertension, psychiatric symptoms and, in the worst cases, quadriplegia. acute attacks, often precipitated by inappropriate drug therapy, are potentially fatal. while earlier workers thought the distal haem biosynthetic enzyme ferrochel ... | 1996 | 8673113 |
| a myxococcus xanthus cell density-sensing system required for multicellular development. | progression through early myxococcus xanthus multicellular fruiting body development requires the generation of and response to extracellular a signal. extracellular a signal is a specific set of amino acids at an extracellular concentration greater than 10 mum. it functions as a cell density signal during starvation that allows the cells to sense that a minimal cell density has been reached and development can proceed. the generation of extracellular a signal requires the products of three asg ... | 1996 | 8674994 |