Publications

evolutionary diversity of ketoacyl synthases in cellulolytic myxobacterium sorangium.	the diversity of type i polyketide synthases (pkss) in cellulolytic myxobacterium sorangium was explored by assaying the ketoacyl synthases (kss) in 10 sorangium strains with two degenerate primer sets and 64 different ks fragments were obtained. for their deduced amino acid sequences, eight were identical to three known kss from sorangium and magnetospirillum, while the others showed 54-83% identities to the modular ks domains reported from various microorganisms. parts of the sorangium kss tig ...	2007	16899349
genome evolution and the emergence of fruiting body development in myxococcus xanthus.	lateral gene transfer (lgt) is thought to promote speciation in bacteria, though well-defined examples have not been put forward.	2007	18159227
social interactions in myxobacterial swarming.	swarming, a collective motion of many thousands of cells, produces colonies that rapidly spread over surfaces. in this paper, we introduce a cell-based model to study how interactions between neighboring cells facilitate swarming. we chose to study myxococcus xanthus, a species of myxobacteria, because it swarms rapidly and has well-defined cell-cell interactions mediated by type iv pili and by slime trails. the aim of this paper is to test whether the cell contact interactions, which are inhere ...	2007	18166072
xanthusbase: adapting wikipedia principles to a model organism database.	xanthusbase (http://www.xanthusbase.org) is the official model organism database (mod) for the social bacterium myxococcus xanthus. in many respects, m.xanthus represents the pioneer model organism (mo) for studying the genetic, biochemical, and mechanistic basis of prokaryotic multicellularity, a topic that has garnered considerable attention due to the significance of biofilms in both basic and applied microbiology research. to facilitate its utility, the design of xanthusbase incorporates ope ...	2007	17090585
aggregation during fruiting body formation in myxococcus xanthus is driven by reducing cell movement.	when starved, myxococcus xanthus cells assemble themselves into aggregates of about 10(5) cells that grow into complex structures called fruiting bodies, where they later sporulate. here we present new observations on the velocities of the cells, their orientations, and reversal rates during the early stages of fruiting body formation. most strikingly, we find that during aggregation, cell velocities slow dramatically and cells orient themselves in parallel inside the aggregates, while later cel ...	2007	17098901
strict specificity for high-mannose type n-glycans and primary structure of a red alga eucheuma serra lectin.	we have elucidated the carbohydrate-binding profile of a non-monosaccharide-binding lectin named eucheuma serra lectin (esa)-2 from the red alga eucheuma serra using a lectin-immobilized column and a centrifugal ultrafiltration-high performance liquid chromatography method with a variety of fluorescence-labeled oligosaccharides. in both methods, esa-2 exclusively bound with high-mannose type (hm) n-glycans, but not with any of other n-glycans including complex type, hybrid type and core pentasac ...	2007	17259190
maintenance of endemicity in urban environments: a hypothesis linking risk, network structure and geography.	in industrialised countries, a rapid epidemic phase of hiv transmission has largely given way to more moderated endemic transmission. the dynamics of endemic transmission may differ substantially from those generating epidemic spread. we hypothesise that three elements play an important role in maintaining endemicity in high prevalence urban environments. first, persons are likely to be subject to multiple risks from multiple sources rather than engaging in a single, hierarchically classified, r ...	2007	17283360
microbiology. bright insight into bacterial gliding.		2007	17289965
evidence that focal adhesion complexes power bacterial gliding motility.	the bacterium myxococcus xanthus has two motility systems: s motility, which is powered by type iv pilus retraction, and a motility, which is powered by unknown mechanism(s). we found that a motility involved transient adhesion complexes that remained at fixed positions relative to the substratum as cells moved forward. complexes assembled at leading cell poles and dispersed at the rear of the cells. when cells reversed direction, the a-motility clusters relocalized to the new leading poles toge ...	2007	17289998
identification of major sporulation proteins of myxococcus xanthus using a proteomic approach.	myxococcus xanthus is a soil-dwelling, gram-negative bacterium that during nutrient deprivation is capable of undergoing morphogenesis from a vegetative rod to a spherical, stress-resistant spore inside a domed-shaped, multicellular fruiting body. to identify proteins required for building stress-resistant m. xanthus spores, we compared the proteome of liquid-grown vegetative cells with the proteome of mature fruiting body spores. two proteins, protein s and protein s1, were differentially expre ...	2007	17293425
lipolytic enzymes in myxococcus xanthus.	the genome of myxococcus xanthus encodes lipolytic enzymes in three different families: patatin lipases, alpha/beta hydrolases, and gdsl lipases. one member of each family was characterized. the protein encoded by mxan_3852 contains motifs characteristic of patatins. mxan_5522 encodes a protein with the g-x-s-x-g motif characteristic of the lipase subfamily of alpha/beta hydrolases. mxan_4569 encodes a member of the gdsl family of lipolytic enzymes. strains with deletions of mxan_5522 and mxan_4 ...	2007	17307851
primary structure and carbohydrate binding specificity of a potent anti-hiv lectin isolated from the filamentous cyanobacterium oscillatoria agardhii.	the primary structure of a lectin, designated oscillatoria agardhii agglutinin (oaa), isolated from the freshwater cyanobacterium o. agardhii nies-204 was determined by the combination of edman degradation and electron spray ionization-mass spectrometry. oaa is a polypeptide (mr 13,925) consisting of two tandem repeats. interestingly, each repeat sequence of oaa showed a high degree of similarity to those of a myxobacterium, myxococcus xanthus hemagglutinin, and a marine red alga eucheuma serra ...	2007	17314091
heat-shock sigma factor rpoh from geobacter sulfurreducens.	recent studies with myxococcus xanthus have suggested that homologues of the escherichia coli heat-shock sigma factor, rpoh, may not be involved in the heat-shock response in this delta-proteobacterium. the genome of another delta-proteobacterium, geobacter sulfurreducens, which is considered to be a representative of the fe(iii)-reducing geobacteraceae that predominate in a diversity of subsurface environments, contains an rpoh homologue. characterization of the g. sulfurreducens rpoh homologue ...	2007	17322204
bithiazole metabolites from the myxobacterium myxococcus fulvus.	two new bithiazole metabolites (3, 4) along with the previously reported compounds (1, 2) were isolated from the culture broth of the gliding bacterium myxococcus fulvus collected from a korean soil. the structures of these compounds were determined to be analogous to myxothiazole a on the basis of combined spectroscopic analyses. the new compounds exhibited significant cytotoxicity and moderate antifungal activity against the mouse fibloblast cell-line l929 and candida albicans, respectively. t ...	2007	17329897
the structure of the escherichia coli nucleoside diphosphate kinase reveals a new quaternary architecture for this enzyme family.	nucleoside diphosphate kinase (ndpk) catalyzes the transfer of gamma-phosphate from nucleoside triphosphates to nucleoside diphosphates. the subunit folding and the dimeric basic structural unit are remarkably the same for available structures but, depending on species, dimers self-associate to form hexamers or tetramers. the crystal structure of the escherichia coli ndpk reveals a new tetrameric quaternary structure for this protein family. the two tetramers differ by the relative orientation o ...	2007	17330300
3-hydroxy-3-methylglutaryl-coa-like synthases direct the formation of methyl and ethyl side groups in the biosynthesis of the antibiotic myxovirescin a.		2007	17330904
regulation of dev, an operon that includes genes essential for myxococcus xanthus development and crispr-associated genes and repeats.	expression of dev genes is important for triggering spore differentiation inside myxococcus xanthus fruiting bodies. dna sequence analysis suggested that dev and cas (crispr-associated) genes are cotranscribed at the dev locus, which is adjacent to crispr (clustered regularly interspaced short palindromic repeats). analysis of rna from developing m. xanthus confirmed that dev and cas genes are cotranscribed with a short upstream gene and at least two repeats of the downstream crispr, forming the ...	2007	17369305
genome-wide high-throughput mining of natural-product biosynthetic gene clusters by phage display.	we have developed a phage-display method for high-throughput mining of bacterial gene clusters encoding the natural-product biosynthetic enzymes, polyketide synthases (pkss) and nonribosomal peptide synthetases (nrpss). this method uses the phosphopantetheinyl transferase activity of sfp to specifically biotinylate nrps and pks carrier-protein domains expressed from a library of random genome fragments fused to a gene encoding a phage coat protein. subsequently, the biotinylated phages are enric ...	2007	17379145
a scaleable manufacturing process for pro-ep-b2, a cysteine protease from barley indicated for celiac sprue.	celiac sprue is an inflammatory disease of the small intestine triggered by ingestion of dietary gluten, a family of glutamine and proline rich proteins found in common foodgrains such as wheat, rye, and barley. one potential therapy for this lifelong disease anticipates using an oral protease to detoxify gluten in vivo. recent studies have shown that ep-b2 (endoprotease b, isoform 2) from barley is a promising example of such a glutenase, thus warranting its large-scale production for animal sa ...	2007	17385743
ecological variables affecting predatory success in myxococcus xanthus.	the feeding efficiency of microbial predators depends on both the availability of various prey species and abiotic variables. myxococcus xanthus is a bacterial predator that searches for microbial prey by gliding motility, and then kills and lyses its prey with secreted compounds. we manipulated three ecological variables to examine their effects on the predatory performance of m. xanthus to better understand its behavior and how it affects prey populations. experiments were designed to determin ...	2007	17410395
consolidation of degraded ornamental porous limestone stone by calcium carbonate precipitation induced by the microbiota inhabiting the stone.	although it has already been shown that calcareous stone can be consolidated by using a bacterially inoculated culture medium, a more user-friendly method is the in situ application of a sterile culture medium that is able to activate, among the microbial community of the stone, those bacteria with a potential for calcium carbonate precipitation. in order to test this new method for stone consolidation, non-sterilized decayed porous limestone was immersed in sterile nutritional media. results we ...	2007	17418886
biology by numbers: mathematical modelling in developmental biology.	in recent years, mathematical modelling of developmental processes has earned new respect. not only have mathematical models been used to validate hypotheses made from experimental data, but designing and testing these models has led to testable experimental predictions. there are now impressive cases in which mathematical models have provided fresh insight into biological systems, by suggesting, for example, how connections between local interactions among system components relate to their wide ...	2007	17440530
characterization of safc, a catechol 4-o-methyltransferase involved in saframycin biosynthesis.	members of the saframycin/safracin/ecteinascidin family of peptide natural products are potent antitumor agents currently under clinical development. saframycin mx1, from myxococcus xanthus, is synthesized by a nonribosomal peptide synthetase, safab, and an o-methyltransferase, safc, although other proteins are likely involved in the pathway. safc was overexpressed in escherichia coli, purified to homogeneity, and assayed for its ability to methylate a variety of substrates. safc was able to cat ...	2007	17449703
combinatorial regulation of genes essential for myxococcus xanthus development involves a response regulator and a lysr-type regulator.	myxococcus xanthus is a bacterium that undergoes multicellular development. c-signaling influences gene expression and movement of cells into aggregates. expression of the dev operon, which includes genes essential for efficient sporulation, depends in part on c-signaling and reaches its highest level in cells within aggregates, ensuring that spores form within fruiting bodies. here, an upstream dna element was found to be essential for dev promoter activity and was bound by frua, a response reg ...	2007	17470804
differential expression of the three multicopper oxidases from myxococcus xanthus.	myxococcus xanthus is a soil bacterium that undergoes a unique life cycle among the prokaryotes upon starvation, which includes the formation of macroscopic structures, the fruiting bodies, and the differentiation of vegetative rods into coccoid myxospores. this peculiarity offers the opportunity to study the copper response in this bacterium in two different stages. in fact, m. xanthus vegetative rods exhibit 15-fold-greater resistance against copper than developing cells. however, cells pre-ad ...	2007	17483223
multicellular development in myxococcus xanthus is stimulated by predator-prey interactions.	myxococcus xanthus is a predatory bacterium that exhibits complex social behavior. the most pronounced behavior is the aggregation of cells into raised fruiting body structures in which cells differentiate into stress-resistant spores. in the laboratory, monocultures of m. xanthus at a very high density will reproducibly induce hundreds of randomly localized fruiting bodies when exposed to low nutrient availability and a solid surface. in this report, we analyze how m. xanthus fruiting body deve ...	2007	17513469
an atypical receiver domain controls the dynamic polar localization of the myxococcus xanthus social motility protein frzs.	the myxococcus xanthus frzs protein transits from pole-to-pole within the cell, accumulating at the pole that defines the direction of movement in social (s) motility. here we show using atomic-resolution crystallography and nmr that the frzs receiver domain (rd) displays the conserved switch tyr102 in an unusual conformation, lacks the conserved asp phosphorylation site, and fails to bind mg(2+) or the phosphoryl analogue, mg(2+) x bef(3). mutation of asp55, closest to the canonical site of rd ...	2007	17573816
frzz, a dual chey-like response regulator, functions as an output for the frz chemosensory pathway of myxococcus xanthus.	myxococcus xanthus utilizes two distinct motility systems for movement (gliding) on solid surfaces: adventurous motility (a-motility) and social motility (s-motility). both systems are regulated by the frz signal transduction pathway, which controls cell reversals required for directed motility and fruiting body formation. the frz chemosensory system, unlike the escherichia coli chemotaxis system, contains proteins with multiple response regulator domains: frze, a chea-chey hybrid protein, and f ...	2007	17581122
mutational analysis of the myxovirescin biosynthetic gene cluster reveals novel insights into the functional elaboration of polyketide backbones.	it has been proposed that two acyl carrier proteins (acps)-tab and tae--and two 3-hydroxy-3-methylglutaryl synthases (hmgss)--tac and taf--could constitute two functional acp-hmgs pairs (tab/tac and tae/taf) responsible for the incorporation of acetate and propionate units into the myxovirescin a scaffold, leading to the formation of beta-methyl and beta-ethyl groups, respectively. it has been suggested that three more proteins--tax and tay, which are members of the superfamily of enoyl-coa hydr ...	2007	17583882
two localization motifs mediate polar residence of frzs during cell movement and reversals of myxococcus xanthus.	myxococcus xanthus utilizes two motility systems for surface locomotion: a-motility and s-motility. s-motility is mediated by extension and retraction of type iv pili. cells exhibiting s-motility periodically reverse by switching the assembly of type iv pili from the old leading pole to the new leading pole. these cellular reversals involve regulated pole-to-pole oscillations of the frzs protein. we constructed and characterized in-frame deletion mutations in several frzs domains to determine th ...	2007	17590236
the elusive engine in myxococcus xanthus gliding motility.	bacterial motility is essential for chemotaxis, virulence and complex social interactions leading to biofilm and fruiting body formation. although bacterial swimming in liquids with a flagellum is well understood, little is known regarding bacterial movements across solid surfaces. gliding motility, one such mode of locomotion, has remained largely mysterious because cells move smoothly along their long axis in the absence of any visible organelle. in this review, i discuss recent evidence that ...	2007	17653507
incorporation of nonmethyl branches by isoprenoid-like logic: multiple beta-alkylation events in the biosynthesis of myxovirescin a1.	several polyketide secondary metabolites are predicted to undergo isoprenoid-like beta-alkylations during biosynthesis. one such secondary metabolite is myxovirescin a1, produced by myxococcus xanthus. myxovirescin is of special interest in that it appears to undergo two distinct beta-alkylations. additionally, the myxovirescin biosynthetic gene cluster lacks tandem thiolation domains required in the synthesis of other beta-branched secondary metabolites. to probe the origins of the beta-branche ...	2007	17656320
triple mutants uncover three new genes required for social motility in myxococcus xanthus.	the bacterium myxococcus xanthus glides over surfaces using two different locomotive mechanisms, called s (social) and a (adventurous) motility that enable cells to move both as groups and as individuals. neither mechanism involves flagella. the functions of these two motors are coordinated by the activity of a small ras-like protein, encoded by the mgla gene. the results of previous studies of a second-site suppressor of the mgla-8 missense mutation mask-815 indicate that mgla interacts with a ...	2007	17660550
cooperation of two carotene desaturases in the production of lycopene in myxococcus xanthus.	in myxococcus xanthus, all known carotenogenic genes are grouped together in the gene cluster carb-cara, except for one, crtib (previously named carc). we show here that the first three genes of the carb operon, crte, crtia, and crtb, encode a geranygeranyl synthase, a phytoene desaturase, and a phytoene synthase, respectively. we demonstrate also that crtia possesses cis-to-trans isomerase activity, and is able to dehydrogenate phytoene, producing phytofluene and zeta-carotene. unlike the major ...	2007	17662111
the motors powering a-motility in myxococcus xanthus are distributed along the cell body.	two models have been proposed to explain the adventurous gliding motility of myxococcus xanthus: (i) polar secretion of slime and (ii) an unknown motor that uses cell surface adhesion complexes that form periodic attachments along the cell length. gliding movements of the leading poles of cephalexin-treated filamentous cells were observed but not equivalent movements of the lagging poles. this demonstrates that the adventurous-motility motors are not confined to the rear of the cell.	2007	17704221
the structure of the carbohydrate backbone of the lps from myxococcus xanthus strain dk1622.	gram-negative rod shaped bacterium myxococcus xanthus dk1622 produces a smooth-type lps. the structure of the polysaccharide o-chain and the core-lipid a region of the lps has been determined by chemical and spectroscopic methods. the o-chain was built up of disaccharide repeating units having the following structure: -->6)-alpha-d-glcp-(1-->4)-alpha-d-galpnac6ome*-(1--> with partially methylated galnac residue. the core region consisted of a phosphorylated hexasaccharide, containing one kdo res ...	2007	17709100
new locus important for myxococcus social motility and development.	the mts locus in salt-tolerant myxococcus fulvus hw-1 was found to be critical for gliding motility, fruiting-body formation, and sporulation. the homologous genes in myxococcus xanthus are also important for social motility and fruiting-body development. the mts genes were determined to be involved in cell-cell cohesion in both myxobacterial species.	2007	17720782
proteins associated with the myxococcus xanthus extracellular matrix.	fruiting body formation of myxococcus xanthus, like biofilm formation of many other organisms, involves the production of an extracellular matrix (ecm). while the polysaccharide component has been studied, the protein component has been largely unexplored. proteins associated with the ecm were solubilized from purified ecm by boiling with sodium dodecyl sulfate and were identified by liquid chromatography-tandem mass spectrometry of tryptic fragments. the ecm is enriched in proteins of novel fun ...	2007	17766415
the myxococcus xanthus developmental program can be delayed by inhibition of dna replication.	under conditions of nutrient deprivation, myxococcus xanthus undergoes a developmental process that results in the formation of a fruiting body containing environmentally resistant myxospores. we have shown that myxospores contain two copies of the genome, suggesting that cells must replicate the genome prior to or during development. to further investigate the role of dna replication in development, a temperature-sensitive dnab mutant, dnab(a116v), was isolated from m. xanthus. unlike what happ ...	2007	17905977
the myxococcus xanthus nla4 protein is important for expression of stringent response-associated genes, ppgpp accumulation, and fruiting body development.	changes in gene expression are important for the landmark morphological events that occur during myxococcus xanthus fruiting body development. enhancer binding proteins (ebps), which are transcriptional activators, play prominent roles in the coordinated expression of developmental genes. a mutation in the ebp gene nla4 affects the timing of fruiting body formation, the morphology of mature fruiting bodies, and the efficiency of sporulation. in this study, we showed that the nla4 mutant accumula ...	2007	17905995
spatial organization of myxococcus xanthus during fruiting body formation.	microcinematography was used to examine fruiting body development of myxococcus xanthus. wild-type cells progress through three distinct phases: a quiescent phase with some motility but little aggregation (0 to 8 h), a period of vigorous motility leading to raised fruiting bodies (8 to 16 h), and a period of maturation during which sporulation is initiated (16 to 48 h). fruiting bodies are extended vertically in a series of tiers, each involving the addition of a cell monolayer on top of the upp ...	2007	17921303
chemosensory pathways, motility and development in myxococcus xanthus.	the complex life cycle of myxococcus xanthus includes predation, swarming, fruiting-body formation and sporulation. the genome of m. xanthus is large and comprises an estimated 7,400 open reading frames, of which approximately 605 code for regulatory genes. these include eight clusters of chemotaxis-like genes that define eight chemosensory pathways, most of which have dedicated functions. although many of these chemosensory pathways have a role in controlling motility, at least two of these pat ...	2007	17922045
coupling of protein localization and cell movements by a dynamically localized response regulator in myxococcus xanthus.	myxococcus xanthus cells harbor two motility machineries, type iv pili (tfp) and the a-engine. during reversals, the two machineries switch polarity synchronously. we present a mechanism that synchronizes this polarity switching. we identify the required for motility response regulator (romr) as essential for a-motility. romr localizes in a bipolar, asymmetric pattern with a large cluster at the lagging cell pole. the large romr cluster relocates to the new lagging pole in parallel with cell rev ...	2007	17932488
mutasynthesis-derived myxalamids and origin of the isobutyryl-coa starter unit of myxalamid b.	myxalamids are potent inhibitors of the eukaryotic electron transport chain produced by different myxobacteria. here, we describe the identification of the myxalamid biosynthesis gene cluster from myxococcus xanthus. additionally, new myxalamids (5-13) have been obtained by mutasynthesis from bkd mutants of m. xanthus and stigmatella aurantiaca. moreover, as these bkd mutants are still able to produce myxalamid b (2), the origin of the isobutyryl-coa (ib-coa) starter unit required for its biosyn ...	2007	17955482
complete genome sequence of the myxobacterium sorangium cellulosum.	the genus sorangium synthesizes approximately half of the secondary metabolites isolated from myxobacteria, including the anti-cancer metabolite epothilone. we report the complete genome sequence of the model sorangium strain s. cellulosum so ce56, which produces several natural products and has morphological and physiological properties typical of the genus. the circular genome, comprising 13,033,779 base pairs, is the largest bacterial genome sequenced to date. no global synteny with the genom ...	2007	17965706
polarity of motility systems in myxococcus xanthus.	myxococcus xanthus is a gliding bacterium that contains two motility systems: s-motility, powered by polar type iv pili, and a-motility, powered by uncharacterized motors and adhesion complexes. the localization and coordination of the two motility engines is essential for directed motility as cells move forward and reverse. during cell reversals, the polarity and localization of motility proteins are rapidly inverted, rendering this system a fascinating example of dynamic protein localization.	2007	17981496
transposon insertions of magellan-4 that impair social gliding motility in myxococcus xanthus.	myxococcus xanthus has two different mechanisms of motility, adventurous (a) motility, which permits individual cells to glide over solid surfaces, and social (s) motility, which permits groups of cells to glide. to identify the genes involved in s-gliding motility, we mutagenized a delta aglu (a-) strain with the defective transposon, magellan-4, and screened for s- mutants that form nonmotile colonies. sequence analysis of the sites of the magellan-4 insertions in these mutants and the alignme ...	2006	16299386
myxococcus xanthus twin-arginine translocation system is important for growth and development.	the twin-arginine translocation (tat) system serves to export fully folded proteins across the cytoplasmic membrane. in many bacteria, three major components, tata, tatb and tatc, are the functionally essential constituents of the tat system. a myxococcus xanthus tatb-tatc deletion mutant could aggregate and form mounds, but was unable to form fruiting bodies under nutritionally limiting conditions. when tatb-tatc mutant vegetative cells were cultured with 0.5 m glycerol, the cell morphology cha ...	2006	16331440
differential effects of chemoreceptor methylation-domain mutations on swarming and development in the social bacterium myxococcus xanthus.	the soil bacterium myxococcus xanthus is a model organism for the study of multicellular behaviour and development in bacteria. m. xanthus cells move on solid surfaces by gliding motility, periodically reversing their direction of movement. motility is co-ordinated to allow cells to effectively feed on macromolecules or prey bacteria when nutrients are plentiful and to form developmental fruiting bodies when nutrients are limiting. the frz signal transduction pathway regulates cellular movements ...	2006	16359317
mutational analysis of the myxococcus xanthus omega4406 promoter region reveals an upstream negative regulatory element that mediates c-signal dependence.	c signaling plays a key role in coordinating cell movement and differentiation during the multicellular developmental process of myxococcus xanthus. c signaling regulates expression of genes induced after about 6 h into development, when cells are forming mounds. one gene whose expression depends absolutely on c signaling was identified by insertion of a transposable element at site omega4406 which generated a transcriptional fusion between lacz and an upstream promoter. we have investigated reg ...	2006	16385042
contribution of the cyclic nucleotide phosphodiesterases pdea and pdeb to adaptation of myxococcus xanthus cells to osmotic or high-temperature stress.	a tblastn search of the myxococcus xanthus genome database at the institute for genomic research (tigr) identified three genes (pdea, pdeb, and pdec) that encode proteins homologous to 3',5'-cyclic nucleotide phosphodiesterase. pdea, pdeb, and pdec mutants, constructed by replacing a part of the gene with the kanamycin or tetracycline resistance gene, showed normal growth, development, and germination under nonstress conditions. however, the spores of mutants, especially the pdea and pdeb mutant ...	2006	16385075
role of sigmad in regulating genes and signals during myxococcus xanthus development.	starvation-induced development of myxococcus xanthus is an excellent model for biofilm formation because it involves cell-cell signaling to coordinate formation of multicellular mounds, gene expression, and cellular differentiation into spores. the role of sigma(d), an alternative sigma factor important for viability in stationary phase and for stress responses, was investigated during development by measuring signal production, gene expression, and sporulation of a sigd null mutant alone and up ...	2006	16621817
genetic population structure of the soil bacterium myxococcus xanthus at the centimeter scale.	myxococcus xanthus is a gram-negative soil bacterium best known for its remarkable life history of social swarming, social predation, and multicellular fruiting body formation. very little is known about genetic diversity within this species or how social strategies might vary among neighboring strains at small spatial scales. to investigate the small-scale population structure of m. xanthus, 78 clones were isolated from a patch of soil (16 by 16 cm) in tübingen, germany. among these isolates, 2 ...	2006	16672510
a myxobacterial s-motility protein dances with poles.	coordinated movement of packs of s-motile myxococcus xanthus cells relies on extrusion and retraction of pili that are located at one cell pole. at regular intervals the pili switch their polar location and cells reverse direction. recently, the frzs s-motility protein was observed to localize predominantly to the piliated pole. in time, frzs was redeployed to the opposite pole and its sequestration at the new site coincided with cell reversal. the c-terminal region of frzs, a response regulator ...	2006	16677816
a protein ser/thr kinase cascade negatively regulates the dna-binding activity of mrpc, a smaller form of which may be necessary for the myxococcus xanthus development.	the developmental process of myxococcus xanthus is achieved by the expression of a specific set of genes under the influence of developmental signals. mrpc is a member of the crp family of transcription regulators, essential for frua expression during development. the pkn8-pkn14 protein kinase cascade negatively regulates mrpc expression (h. nariya and s. inouye, 2005. mol microbiol 58: 367-379). elevated levels of mrpc in pkn8 and pkn14 deletion strains (deltapkn8 and deltapkn14) induce untimel ...	2006	16689796
comprehensive mutation identification in an evolved bacterial cooperator and its cheating ancestor.	precise characterization of the mutation histories of evolutionary lineages is crucial for understanding the evolutionary process, yet mutation identification has been constrained by traditional techniques. we sought to identify all accumulated mutations in an experimentally evolved lineage of the cooperative bacterium myxococcus xanthus, which constructs fruiting bodies by a process of social multicellular development in response to starvation. this lineage had undergone two major transitions i ...	2006	16707573
sociobiology: the phoenix effect.		2006	16710402
evolution of an obligate social cheater to a superior cooperator.	obligate relationships have evolved many times and can be parasitic or mutualistic. obligate organisms rely on others to survive and thus coevolve with their host or partner. an important but little explored question is whether obligate status is an evolutionarily terminal condition or whether obligate lineages can evolve back to an autonomous lifestyle. the bacterium myxococcus xanthus survives starvation by the social development of spore-bearing fruiting bodies. some m. xanthus genotypes defe ...	2006	16710413
the response regulator phop4 is required for late developmental events in myxococcus xanthus.	phosphate regulation is complex in the developmental prokaryote myxococcus xanthus, and requires at least four two-component systems (tcss). here, the identification and characterization of a member of one tcs, designated phop4, is reported. phop4 insertion and in-frame deletion strains caused spore viability to be decreased by nearly two orders of magnitude, and reduced all three development-specific phosphatase activities by 80-90 % under phosphate-limiting conditions. microarray and quantitat ...	2006	16735725
the orphan response regulator digr is required for synthesis of extracellular matrix fibrils in myxococcus xanthus.	in myxococcus xanthus, two-component systems have crucial roles in regulating motility behavior and development. here we describe an orphan response regulator, consisting of an n-terminal receiver domain and a c-terminal dna binding domain, which is required for a and type iv pilus-dependent gliding motility. genetic evidence suggests that phosphorylation of the conserved, phosphorylatable aspartate residue in the receiver domain is required for digr activity. consistent with the defect in type ...	2006	16740945
cohesion-defective mutants of myxococcus xanthus.	cohesion of myxococcus xanthus cells involves interaction of a cell surface cohesin with a component of the extracellular matrix. in this work, two previously isolated cohesion-defective (fbd) mutants were characterized. the fbda and fbdb genes do not encode the cohesins but are necessary for their production. both mutants produce type iv pili, suggesting that pila is not a major cohesin.	2006	16740967
a novel regulation on developmental gene expression of fruiting body formation in myxobacteria.	myxobacteria are gram-negative soil microorganisms that prey on other microorganisms. myxobacteria have significant potential for applications in biotechnology because of their extraordinary ability to produce natural products such as secondary metabolites. myxobacteria also stand out as model organisms for the study of cell-cell interactions and multicellular development during their complex life cycle. cellular morphogenesis during multicellular development in myxobacteria is very similar to t ...	2006	16791590
rational design of combination enzyme therapy for celiac sprue.	celiac sprue (also known as celiac disease) is an inheritable, gluten-induced enteropathy of the upper small intestine with an estimated prevalence of 0.5%-1% in most parts of the world. the ubiquitous nature of food gluten, coupled with inadequate labeling regulations in most countries, constantly poses a threat of disease exacerbation and relapse for patients. here, we demonstrate that a two-enzyme cocktail comprised of a glutamine-specific cysteine protease (ep-b2) that functions under gastri ...	2006	16793522
two ser/thr protein kinases essential for efficient aggregation and spore morphogenesis in myxococcus xanthus.	myxococcus xanthus has a complex life cycle that involves vegetative growth and development. previously, we described the espab locus that is involved in timing events during the initial stages of fruiting body formation. deletion of espa caused early aggregation and sporulation, whereas deletion of espb caused delayed aggregation and sporulation resulting in reduced spore yields. in this study, we describe two genes, pkta5 and pktb8, that flank the espab locus and encode ser/thr protein kinase ...	2006	16796678
two continuum models for the spreading of myxobacteria swarms.	we analyze the phenomenon of spreading of a myxococcus xanthus bacterial colony on plates coated with nutrient. the bacteria spread by gliding on the surface. in the first few hours, cell growth is irrelevant to colony spread. in this case, bacteria spread through peninsular protrusions from the edge of the initial colony. we analyze the diffusion through the narrowing reticulum of cells on the surface mathematically and derive formulae for the spreading rates. on the time scale of tens of hours ...	2006	16802086
unidirectional movement of flares of cells of myxococcus xanthus.	amongst other modes, myxococcal cells move in swarms that are flares or columns of cells. it has been argued that this is a strategy allowing a large enough number of them to encounter food bacteria. then, the combined large amount of extracellular lytic enzymes from the mass of cells can provide adequate nutrient resources from the food bacteria for all the myxococci of the swarm. however, how they move as a coherent column has not been adequately explained. here based on the idea that a rare c ...	2006	16809232
regulation of the myxococcus xanthus c-signal-dependent omega4400 promoter by the essential developmental protein frua.	the bacterium myxococcus xanthus employs extracellular signals to coordinate aggregation and sporulation during multicellular development. extracellular, contact-dependent signaling that involves the csga protein (called c-signaling) activates frua, a putative response regulator that governs a branched signaling pathway inside cells. one branch regulates cell movement, leading to aggregation. the other branch regulates gene expression, leading to sporulation. c-signaling is required for full exp ...	2006	16816188
a microbial genetic journey.	fortunately, i began research in 1950 when the basic concepts of microbial genetics could be explored experimentally. i began with bacteriophage lambda and tried to establish the colinearity of its linkage map with its dna molecule. my students and i worked out the regulation of lambda repressor synthesis for the establishment and maintenance of lysogeny. we also investigated the proteins responsible for assembly of the phage head. using cell extracts, we discovered how to package dna inside the ...	2006	16824011
[induction of bacillus anthracis hemolytic activity with the use of myxococcus xanthus].	the development of a new method for the induction of the b. anthracis hemolytic activity with the use of m. xanthus and the differentiation of pure cultures of the causative agent of anthrax from those contaminated with myxobacteria is presented. to demonstrate the induction of the hemolytic acivity of b. anthracis with the use of m. xanthus, conditions for the symbiosis of b. anthracis cells sti, exhibiting no hemolytic activity, with m. xanthus non-hemolytic cells were created by mixing them a ...	2006	16830581
myxovirescin a biosynthesis is directed by hybrid polyketide synthases/nonribosomal peptide synthetase, 3-hydroxy-3-methylglutaryl-coa synthases, and trans-acting acyltransferases.	myxococcus xanthus dk1622 is shown to be a producer of myxovirescin (antibiotic ta) antibiotics. the myxovirescin biosynthetic gene cluster spans at least 21 open reading frames (orfs) and covers a chromosomal region of approximately 83 kb. in silico analysis of myxovirescin orfs in conjunction with genetic studies suggests the involvement of four type i polyketide synthases (pkss; tai, tal, tao, and tap), one major hybrid pks/nrps (ta-1), and a number of monofunctional enzymes similar to the on ...	2006	16835859
distinguishing features of delta-proteobacterial genomes.	we analyzed several features of five currently available delta-proteobacterial genomes, including two aerobic bacteria exhibiting predatory behavior and three anaerobic sulfate-reducing bacteria. the delta genomes are distinguished from other bacteria by several properties: (i) the delta genomes contain two "giant" s1 ribosomal protein genes in contrast to all other bacterial types, which encode a single or no s1; (ii) in most delta-proteobacterial genomes the major ribosomal protein (rp) gene c ...	2006	16844781
straight-chain fatty acids are dispensable in the myxobacterium myxococcus xanthus for vegetative growth and fruiting body formation.	inactivation of the mxan_0853 gene blocked the production in myxococcus xanthus of straight-chain fatty acids which otherwise represent 30% of total fatty acids. despite this drastic change in the fatty acid profile, no change in phenotype could be observed, which contrasts with previous interpretations of the role of straight-chain fatty acids in the organism's development.	2006	16855254
type iv pili function upstream of the dif chemotaxis pathway in myxococcus xanthus eps regulation.	the developmental bacterium myxococcus xanthus utilizes gliding motility to aggregate during the formation of multicellular fruiting bodies. the social (s) component of m. xanthus gliding motility requires at least two extracellular surface structures, type iv pili (tfp) and the fibril polysaccharide or exopolysaccharide (eps). retraction of tfp is proposed to power s motility and eps from neighbouring cells is suggested to provide an anchor and trigger for tfp retraction. the production of eps ...	2006	16856943
recruitment of a novel zinc-bound transcriptional factor by a bacterial hmga-type protein is required for regulating multiple processes in myxococcus xanthus.	enhanceosome assembly in eukaryotes often requires high mobility group a (hmga) proteins. in prokaryotes, the only known transcriptional regulator with hmga-like physical, structural and dna-binding properties is myxococcus xanthus card. here, we report that every card-regulated process analysed also requires the product of gene carg, located immediately downstream of and transcriptionally coupled to card. carg has the zinc-binding h/c-rich metallopeptidase motif found in archaemetzincins, but w ...	2006	16879646
rippling is a predatory behavior in myxococcus xanthus.	cells of myxococcus xanthus will, at times, organize their movement such that macroscopic traveling waves, termed ripples, are formed as groups of cells glide together on a solid surface. the reason for this behavior has long been a mystery, but we demonstrate here that rippling is a feeding behavior which occurs when m. xanthus cells make direct contact with either prey or large macromolecules. rippling has been observed during two fundamentally distinct environmental conditions: (i) starvation ...	2006	16885457
genetic control for light-induced carotenoid production in non-phototrophic bacteria.	carotenoids are naturally occurring yellow or orange pigments that serve as a protectant against photo-oxidative damages. among the wide variety of producers, the prokaryotes generate a broad spectrum of carotenoids with diverse chemical structures that are expected to have a high potential in biotechnological applications. bacterial carotenogenesis occurs in a constitutive or light-induced manner, which suggests the diversity of the regulatory mechanism. the mechanism for light-induced caroteno ...	2006	16091943
the unique dkxanthene secondary metabolite family from the myxobacterium myxococcus xanthus is required for developmental sporulation.	under starvation conditions myxobacteria form multicellular fruiting bodies in which vegetative cells differentiate into heat- and desiccation-resistant myxospores. myxobacteria in general are a rich source of secondary metabolites that often exhibit biological activities rarely found in nature. although the involvement of a yellow compound in sporulation and fruiting body formation of myxococcus xanthus was described almost 30 years ago, the chemical principle of the pigment remained elusive. t ...	2006	17148609
phospholipid directed motility of surface-motile bacteria.	myxococcus xanthus is a surface-motile bacterium that has adapted at least one chemosensory system to allow directed movement towards the slowly diffusible lipid phosphatidylethanolamine (pe). the dif chemosensory pathway is remarkable because it has at least three inputs coupled to outputs that control extracellular matrix (ecm) production and lipid chemotaxis. the methyl-accepting chemotaxis protein, difa, has two different sensor inputs that have been localized by mutagenesis. the dif chemose ...	2006	16925549
fiba and pila act cooperatively during fruiting body formation of myxococcus xanthus.	the extracellular matrix (ecm) of myxococcus xanthus is essential for social (s-) motility and fruiting body formation. an ecm-bound protein, fiba, is homologous to m4 zinc metalloproteases and is important for stimulation by a phosphatidylethanolamine (pe) chemoattractant and for formation of discrete aggregation foci. in this work, we demonstrate that a correlation exists between a reduced ability to respond to pe and the observed defects in fruiting body morphogenesis. furthermore, the fiba a ...	2006	16925559
3-hydroxy-3-methylglutaryl-coenzyme a (coa) synthase is involved in biosynthesis of isovaleryl-coa in the myxobacterium myxococcus xanthus during fruiting body formation.	isovaleryl-coenzyme a (iv-coa) is the starting unit for some secondary metabolites and iso-odd fatty acids in several bacteria. according to textbook biochemistry, iv-coa is derived from leucine degradation, but recently an alternative pathway that branches from the well-known mevalonate-dependent isoprenoid biosynthesis has been described for myxobacteria. a double mutant was constructed in myxococcus xanthus by deletion of genes involved in leucine degradation and disruption of mvas encoding t ...	2006	16952943
a square archaeon, the smallest eukaryote and the largest bacteria.		2006	16958749
novel iso-branched ether lipids as specific markers of developmental sporulation in the myxobacterium myxococcus xanthus.	iso-fatty acids (fas) are the dominant fa family in all myxobacteria analyzed. furthermore, it was postulated that iso-fas or compounds derived thereof are involved in fruiting body formation in myxococcus xanthus, since mutants with a reduced level of iso-fa due to a reduced level of the precursor isovaleryl-coa, are delayed in aggregation and produce only few myxospores. to elucidate the function of iso-fas and their corresponding lipids we have analyzed the developmental phenotype of mutants ...	2006	16990257
cbga, a protein involved in cortex formation and stress resistance in myxococcus xanthus spores.	cbga plays a role in cortex formation and the acquisition of a subset of stress resistance properties in myxococcus xanthus spores. the cbga mutant produces spores with thin or no cortex layers, and these spores are more sensitive to heat and sodium dodecyl sulfate than their wild-type counterparts.	2006	16997953
reconstitution of the myxothiazol biosynthetic gene cluster by red/et recombination and heterologous expression in myxococcus xanthus.	although many secondary metabolites exhibiting important pharmaceutical and agrochemical activities have been isolated from myxobacteria, most of these microorganisms remain difficult to handle genetically. to utilize their metabolic potential, heterologous expression methodologies are currently being developed. here, the red/et recombination technology was used to perform all required gene cluster engineering steps in escherichia coli prior to the transfer into the chromosome of the heterologou ...	2006	16997979
byssovorax cruenta gen. nov., sp. nov., nom. rev., a cellulose-degrading myxobacterium: rediscovery of 'myxococcus cruentus' thaxter 1897.	a rare, cellulose-decomposing myxobacterium is described, and a new genus name, byssovorax, is proposed for it. the organism is almost certainly identical to the species 'myxococcus cruentus' thaxter 1897, and that species epithet is therefore revived for the novel bacterium: the type strain of byssovorax cruenta gen. nov., sp. nov., nom. rev. is strain by c2(t) (=dsm 14553(t)=cip 108850(t)). the g+c content of its dna is 69.9 mol%. the 16s rrna gene sequence shows that the species belongs to th ...	2006	17012562
novel lipids in myxococcus xanthus and their role in chemotaxis.	organisms that colonize solid surfaces, like myxococcus xanthus, use novel signalling systems to organize multicellular behaviour. phosphatidylethanolamine (pe) containing the fatty acid 16:1omega5 (delta11) elicits a chemotactic response. the phenomenon was examined by observing the effects of pe species with varying fatty acid pairings. wild-type m. xanthus contains 17 different pe species under vegetative conditions and 19 at the midpoint of development; 13 of the 17 have an unsaturated fatty ...	2006	17014493
evolution of sensory complexity recorded in a myxobacterial genome.	myxobacteria are single-celled, but social, eubacterial predators. upon starvation they build multicellular fruiting bodies using a developmental program that progressively changes the pattern of cell movement and the repertoire of genes expressed. development terminates with spore differentiation and is coordinated by both diffusible and cell-bound signals. the growth and development of myxococcus xanthus is regulated by the integration of multiple signals from outside the cells with physiologi ...	2006	17015832
proteome analysis of myxococcus xanthus by off-line two-dimensional chromatographic separation using monolithic poly-(styrene-divinylbenzene) columns combined with ion-trap tandem mass spectrometry.	myxobacteria are potent producers of secondary metabolites exhibiting diverse biological activities and pharmacological potential. the proteome of myxococcus xanthus dk1622 was characterized by two-dimensional chromatographic separation of tryptic peptides from a lysate followed by tandem mass spectrometric identification. the high degree of orthogonality of the separation system employing polymer-based strong cation-exchange and monolithic reversed-phase stationary phases was clearly demonstrat ...	2006	17022647
lysophosphatidylethanolamine is a substrate for the short-chain alcohol dehydrogenase soca from myxococcus xanthus.	short-chain alcohol dehydrogenases (scadhs) synthesize a variety of intercellular signals and other chemically diverse products. it is difficult to predict the substrate of a scadh on the basis of amino acid sequence homology, as the substrates are not known for most scadhs. in myxococcus xanthus, the scadh csga is responsible for c signaling during fruiting body development, although the mechanism is unclear. overexpression of the scadh soca compensates for the lack of csga and restores develop ...	2006	17028273
crystal structure of protoporphyrinogen oxidase from myxococcus xanthus and its complex with the inhibitor acifluorfen.	protoporphyrinogen ix oxidase, a monotopic membrane protein, which catalyzes the oxidation of protoporphyrinogen ix to protoporphyrin ix in the heme/chlorophyll biosynthetic pathway, is distributed widely throughout nature. here we present the structure of protoporphyrinogen ix oxidase from myxococcus xanthus, an enzyme with similar catalytic properties to human protoporphyrinogen ix oxidase that also binds the common plant herbicide, acifluorfen. in the native structure, the planar porphyrinoge ...	2006	17046834
self-organized and highly ordered domain structures within swarms of myxococcus xanthus.	coordinated group movement (swarming) is a key aspect of myxococcus xanthus' social behavior. here we report observation of domain structures formed by multiple cells within large three-dimensional swarming groups grown on amorphous glass substrates, using the atomic force microscope (afm). novel analyses revealed that 90% of the wild type swarms displayed some form of preferential cell alignment. in contrast, cells with mutations in the social and adventurous motility systems displayed a distin ...	2006	16421928
accordion waves in myxococcus xanthus.	myxococcus xanthus are gram-negative bacteria that glide on solid surfaces, periodically reversing their direction of movement. when starved, m. xanthus cells organize their movements into waves of cell density that sweep over the colony surface. these waves are unique: although they appear to interpenetrate, they actually reflect off one another when they collide, so that each wave crest oscillates back and forth with no net displacement. because the waves reflect the coordinated back and forth ...	2006	16432222
gliding motility: anticipating the next move with a molecular clock.	frzs protein is important for normal social motility in myxobacteria, which includes periodic reversals in the direction of cell motion. recent results show that cell reversal correlates with the migration of frzs from the old leading pole of the cell to the new leading pole.	2006	16461268
integration into the phage attachment site, attb, impairs multicellular differentiation in stigmatella aurantiaca.	stigmatella aurantiaca displays a complex developmental life cycle in response to starvation conditions that results in the formation of tree-like fruiting bodies capable of producing spores. the phage mx8, first isolated from the close relative myxococcus xanthus, is unable to infect s. aurantiaca cells and integrate into the genome. however, plasmids containing mx8 fragments encoding the integrase and attp are able to integrate at the attb locus in the s. aurantiaca genome by site-specific rec ...	2006	16484181
nla18, a key regulatory protein required for normal growth and development of myxococcus xanthus.	ntrc-like activators regulate the transcription of a wide variety of adaptive genes in bacteria. previously, we demonstrated that a mutation in the ntrc-like activator gene nla18 causes defects in fruiting body development in myxococcus xanthus. in this report, we describe the effect that nla18 inactivation has on gene expression patterns during development and vegetative growth. gene expression in nla18 mutant cells is altered in the early stages of fruiting body development. furthermore, nla18 ...	2006	16484184
nonribosomal peptide biosynthesis: point mutations and module skipping lead to chemical diversity.		2006	16506259
cyanobacterial response regulator pata contains a conserved n-terminal domain (patan) with an alpha-helical insertion.	the cyanobacterium anabaena (nostoc) pcc 7120 responds to starvation for nitrogen compounds by differentiating approximately every 10th cell in the filament into nitrogen-fixing cells called heterocysts. heterocyst formation is subject to complex regulation, which involves an unusual response regulator pata that contains a chey-like phosphoacceptor (receiver, rec) domain at its c-terminus. pata-like response regulators are widespread in cyanobacteria; one of them regulates phototaxis in synechoc ...	2006	16543275
a new class of [2fe-2s]-cluster-containing protoporphyrin (ix) ferrochelatases.	protoporphyrin (ix) ferrochelatase catalyses the insertion of ferrous iron into protoporphyrin ix to form haem. these ferrochelatases exist as monomers and dimers, both with and without [2fe-2s] clusters. the motifs for [2fe-2s] cluster co-ordination are varied, but in all cases previously reported, three of the four cysteine ligands are present in the 30 c-terminal residues and the fourth ligand is internal. in the present study, we demonstrate that a group of micro-organisms exist which posses ...	2006	16548850
secretins take shape.	secretins are a unique class of bacterial multimeric outer membrane proteins that probably differ considerably from other, less complex outer membrane proteins in their overall structure and organization, and in their requirements for outer membrane targeting and assembly factors. in this microcommentary, we discuss these differences with respect to the role of a specific class of lipoproteins, often referred to as pilotins, in secretin complex assembly. we compare them with other lipoproteins t ...	2006	16556215
polar assembly of the type iv pilus secretin in myxococcus xanthus.	the type iv pilus filament of myxococcus xanthus penetrates the outer membrane through a gated channel--the pilq secretin. assembly of the channel and formation of pilq multimeric complexes that resist disassembly in heated detergent is correlated with the release of a 50 kda fragment of pilq. tgl lipoprotein is required for pilq assembly in m. xanthus, because pilq monomers but no heat and detergent-resistant complexes are present in a strain from which tgl has been deleted. pilq protein is oft ...	2006	16556217