-
Proceedings of the National Academy of... Jun 2020Chemical-induced spores of the Gram-negative bacterium are peptidoglycan (PG)-deficient. It is unclear how these spherical spores germinate into rod-shaped, walled...
Chemical-induced spores of the Gram-negative bacterium are peptidoglycan (PG)-deficient. It is unclear how these spherical spores germinate into rod-shaped, walled cells without preexisting PG templates. We found that germinating spores first synthesize PG randomly on spherical surfaces. MglB, a GTPase-activating protein, forms a cluster that responds to the status of PG growth and stabilizes at one future cell pole. Following MglB, the Ras family GTPase MglA localizes to the second pole. MglA directs molecular motors to transport the bacterial actin homolog MreB and the Rod PG synthesis complexes away from poles. The Rod system establishes rod shape de novo by elongating PG at nonpolar regions. Thus, similar to eukaryotic cells, the interactions between GTPase, cytoskeletons, and molecular motors initiate spontaneous polarization in bacteria.
Topics: Bacterial Proteins; Cell Polarity; Cell Wall; GTPase-Activating Proteins; Microscopy, Electron; Morphogenesis; Myxococcus xanthus; Peptidoglycan; Spores, Bacterial
PubMed: 32513721
DOI: 10.1073/pnas.2001384117 -
Journal of Bacteriology Jul 1995Two recA genes, recA1 and recA2, in Myxococcus xanthus were cloned by using the recA gene of Escherichia coli, and their DNA sequences were determined. On the basis of...
Two recA genes, recA1 and recA2, in Myxococcus xanthus were cloned by using the recA gene of Escherichia coli, and their DNA sequences were determined. On the basis of deduced amino acid sequences, RecA1 and RecA2 have 67.0% identity to each other and 60.5 and 60.9% identities to E. coli RecA, respectively. Expression of recA2 was detected in both vegetative and developmental cells by Northern blot (RNA) analysis, and a threefold induction was observed when cells were treated with nalidixic acid. Repeated attempts to isolate a recA2 disruption mutant have failed, while a recA1 disruption mutant was readily isolated. Both the recA1 and recA2 genes expressed in E. coli complement the UV sensitivity of an E. coli recA strain.
Topics: Amino Acid Sequence; Base Sequence; Blotting, Northern; Cell Division; Cloning, Molecular; Escherichia coli; Gene Expression Regulation, Bacterial; Genes, Bacterial; Molecular Sequence Data; Morphogenesis; Mutagenesis; Myxococcus xanthus; Nalidixic Acid; Rec A Recombinases; Recombination, Genetic; Sequence Analysis, DNA; Sequence Homology, Amino Acid; Species Specificity; Ultraviolet Rays
PubMed: 7608099
DOI: 10.1128/jb.177.14.4179-4182.1995 -
PLoS Genetics Mar 2014Chemosensory systems (CSS) are complex regulatory pathways capable of perceiving external signals and translating them into different cellular behaviors such as motility...
Chemosensory systems (CSS) are complex regulatory pathways capable of perceiving external signals and translating them into different cellular behaviors such as motility and development. In the δ-proteobacterium Myxococcus xanthus, chemosensing allows groups of cells to orient themselves and aggregate into specialized multicellular biofilms termed fruiting bodies. M. xanthus contains eight predicted CSS and 21 chemoreceptors. In this work, we systematically deleted genes encoding components of each CSS and chemoreceptors and determined their effects on M. xanthus social behaviors. Then, to understand how the 21 chemoreceptors are distributed among the eight CSS, we examined their phylogenetic distribution, genomic organization and subcellular localization. We found that, in vivo, receptors belonging to the same phylogenetic group colocalize and interact with CSS components of the respective phylogenetic group. Finally, we identified a large chemosensory module formed by three interconnected CSS and multiple chemoreceptors and showed that complex behaviors such as cell group motility and biofilm formation require regulatory apparatus composed of multiple interconnected Che-like systems.
Topics: Biofilms; Cell Movement; Chemotaxis; Gene Expression Regulation, Bacterial; Movement; Myxococcus xanthus; Phylogeny; Signal Transduction
PubMed: 24603697
DOI: 10.1371/journal.pgen.1004164 -
Applied and Environmental Microbiology Apr 2008Myxobacteria are very important due to their unique characteristics, such as multicellular social behavior and the production of diverse and novel bioactive secondary...
Myxobacteria are very important due to their unique characteristics, such as multicellular social behavior and the production of diverse and novel bioactive secondary metabolites. However, the lack of autonomously replicating plasmids has hindered genetic manipulation of myxobacteria for decades. To determine whether indigenous plasmids are present, we screened about 150 myxobacterial strains, and a circular plasmid designated pMF1 was isolated from Myxococcus fulvus 124B02. Sequence analysis showed that this plasmid was 18,634 bp long and had a G+C content of 68.7%. Twenty-three open reading frames were found in the plasmid, and 14 of them were not homologous to any known sequence. Plasmids containing the gene designated pMF1.14, which encodes a large unknown protein, were shown to transform Myxococcus xanthus DZ1 and DK1622 at high frequencies ( approximately 10(5) CFU/microg DNA), suggesting that the locus is responsible for the autonomous replication of pMF1. Shuttle vectors were constructed for both M. xanthus and Escherichia coli. The pilA gene, which is essential for pilus formation and social motility in M. xanthus, was cloned into the shuttle vectors and introduced into the pilA-deficient mutant DK10410. The transformants subsequently exhibited the ability to form pili and social motility. Autonomously replicating plasmid pMF1 provides a new tool for genetic manipulation in Myxococcus.
Topics: Base Composition; Cloning, Molecular; DNA Replication; DNA, Bacterial; Gene Expression Regulation, Bacterial; Genetic Vectors; Molecular Sequence Data; Myxococcus; Myxococcus xanthus; Open Reading Frames; Plasmids
PubMed: 18245244
DOI: 10.1128/AEM.02143-07 -
Evolution; International Journal of... Apr 2017Epistatic interactions can greatly impact evolutionary phenomena, particularly the process of adaptation. Here, we leverage four parallel experimentally evolved lineages...
Epistatic interactions can greatly impact evolutionary phenomena, particularly the process of adaptation. Here, we leverage four parallel experimentally evolved lineages to study the emergence and trajectories of epistatic interactions in the social bacterium Myxococcus xanthus. A social gene (pilA) necessary for effective group swarming on soft agar had been deleted from the common ancestor of these lineages. During selection for competitiveness at the leading edge of growing colonies, two lineages evolved qualitatively novel mechanisms for greatly increased swarming on soft agar, whereas the other two lineages evolved relatively small increases in swarming. By reintroducing pilA into different genetic backgrounds along the four lineages, we tested whether parallel lineages showed similar patterns of epistasis. In particular, we tested whether a pattern of negative epistasis between accumulating mutations and pilA previously found in the fastest lineage would be found only in the two evolved lineages with the fastest and most striking swarming phenotypes, or rather was due to common epistatic structure across all lineages arising from the generic fixation of adaptive mutations. Our analysis reveals the emergence of negative epistasis across all four independent lineages. Further, we present results showing that the observed negative epistasis is not due exclusively to evolving populations approaching a maximum phenotypic value that inherently limits positive effects of pilA reintroduction, but rather involves direct antagonistic interactions between accumulating mutations and the reintroduced social gene.
Topics: Biological Evolution; Epistasis, Genetic; Genetic Fitness; Mutation; Myxococcus xanthus
PubMed: 28128449
DOI: 10.1111/evo.13190 -
Journal of Evolutionary Biology Feb 2017Understanding how multiple mutations interact to jointly impact multiple ecologically important traits is critical for creating a robust picture of organismal fitness...
Understanding how multiple mutations interact to jointly impact multiple ecologically important traits is critical for creating a robust picture of organismal fitness and the process of adaptation. However, this is complicated by both environmental heterogeneity and the complexity of genotype-to-phenotype relationships generated by pleiotropy and epistasis. Moreover, little is known about how pleiotropic and epistatic relationships themselves change over evolutionary time. The soil bacterium Myxococcus xanthus employs several distinct social traits across a range of environments. Here, we use an experimental lineage of M. xanthus that evolved a novel form of social motility to address how interactions between epistasis and pleiotropy evolve. Specifically, we test how mutations accumulated during selection on soft agar pleiotropically affect several other social traits (hard agar motility, predation and spore production). Relationships between changes in swarming rate in the selective environment and the four other traits varied greatly over time in both direction and magnitude, both across timescales of the entire evolutionary lineage and individual evolutionary time steps. We also tested how a previously defined epistatic interaction is pleiotropically expressed across these traits. We found that phenotypic effects of this epistatic interaction were highly correlated between soft and hard agar motility, but were uncorrelated between soft agar motility and predation, and inversely correlated between soft agar motility and spore production. Our results show that 'epistatic pleiotropy' varied greatly in magnitude, and often even in sign, across traits and over time, highlighting the necessity of simultaneously considering the interacting complexities of pleiotropy and epistasis when studying the process of adaptation.
Topics: Acclimatization; Adaptation, Physiological; Biological Evolution; Epistasis, Genetic; Myxococcus xanthus; Phenotype
PubMed: 27862537
DOI: 10.1111/jeb.12999 -
Journal of Bacteriology Dec 2016Soil bacteria engage each other in competitive and cooperative ways to determine their microenvironments. In this study, we report the identification of a large number...
UNLABELLED
Soil bacteria engage each other in competitive and cooperative ways to determine their microenvironments. In this study, we report the identification of a large number of genes required for Myxococcus xanthus to engage Bacillus subtilis in a predator-prey relationship. We generated and tested over 6,000 individual transposon insertion mutants of M. xanthus and found many new factors required to promote efficient predation, including the specialized metabolite myxoprincomide, an ATP-binding cassette (ABC) transporter permease, and a clustered regularly interspaced short palindromic repeat (CRISPR) locus encoding bacterial immunity. We also identified genes known to be involved in predation, including those required for the production of exopolysaccharides and type IV pilus (T4P)-dependent motility, as well as chemosensory and two-component systems. Furthermore, deletion of these genes confirmed their role during predation. Overall, M. xanthus predation appears to be a multifactorial process, with multiple determinants enhancing predation capacity.
IMPORTANCE
Soil bacteria engage each other in complex environments and utilize multiple traits to ensure survival. Here, we report the identification of multiple traits that enable a common soil organism, Myxococcus xanthus, to prey upon and utilize nutrients from another common soil organism, Bacillus subtilis We mutagenized the predator and carried out a screen to identify genes that were required to either enhance or diminish capacity to consume prey. We identified dozens of genes encoding factors that contribute to the overall repertoire for the predator to successfully engage its prey in the natural environment.
Topics: Bacillus subtilis; Bacterial Proteins; Clustered Regularly Interspaced Short Palindromic Repeats; Gene Expression Regulation, Bacterial; Mutagenesis, Insertional; Myxococcus xanthus
PubMed: 27698086
DOI: 10.1128/JB.00575-16 -
Microbiology (Reading, England) Apr 2020Myxobacteria exhibit complex social behaviors such as predation, outer membrane exchange and fruiting body formation. These behaviors depend on coordinated movements of...
Myxobacteria exhibit complex social behaviors such as predation, outer membrane exchange and fruiting body formation. These behaviors depend on coordinated movements of cells on solid surfaces that involve social (S) motility. S-motility is powered by extension-retraction cycles of type 4 pili (Tfp) and exopolysaccharides (EPS) that provide a matrix for group cellular movement. Here, we characterized a new class of S-motility mutants in . These mutants have a distinctive phenotype: they lack S-motility even though they produce pili and EPS and the phenotype is temperature-sensitive. The point mutations were mapped to a single locus, MXAN_3284, named . Similar to mutants, mutants are hyperpiliated and, strikingly, the temperature-sensitive phenotype is caused by null mutations. Our results indicate that SglT plays a critical role in Tfp function associated with pilus retraction and that the block in pili retraction is caused by a Tfp assembly defect in the absence of SglT at high-temperature growth.
Topics: Bacterial Proteins; Cytosol; Fimbriae Proteins; Fimbriae, Bacterial; Movement; Mutation; Myxococcus xanthus; Polysaccharides, Bacterial; Protein Multimerization; Temperature
PubMed: 32039748
DOI: 10.1099/mic.0.000893 -
Microbiology and Molecular Biology... Sep 1999Gliding motility is observed in a large variety of phylogenetically unrelated bacteria. Gliding provides a means for microbes to travel in environments with a low water... (Review)
Review
Gliding motility is observed in a large variety of phylogenetically unrelated bacteria. Gliding provides a means for microbes to travel in environments with a low water content, such as might be found in biofilms, microbial mats, and soil. Gliding is defined as the movement of a cell on a surface in the direction of the long axis of the cell. Because this definition is operational and not mechanistic, the underlying molecular motor(s) may be quite different in diverse microbes. In fact, studies on the gliding bacterium Myxococcus xanthus suggest that two independent gliding machineries, encoded by two multigene systems, operate in this microorganism. One machinery, which allows individual cells to glide on a surface, independent of whether the cells are moving alone or in groups, requires the function of the genes of the A-motility system. More than 37 A-motility genes are known to be required for this form of movement. Depending on an additional phenotype, these genes are divided into two subclasses, the agl and cgl genes. Videomicroscopic studies on gliding movement, as well as ultrastructural observations of two myxobacteria, suggest that the A-system motor may consist of multiple single motor elements that are arrayed along the entire cell body. Each motor element is proposed to be localized to the periplasmic space and to be anchored to the peptidoglycan layer. The force to glide which may be generated here is coupled to adhesion sites that move freely in the outer membrane. These adhesion sites provide a specific contact with the substratum. Based on single-cell observations, similar models have been proposed to operate in the unrelated gliding bacteria Flavobacterium johnsoniae (formerly Cytophaga johnsonae), Cytophaga strain U67, and Flexibacter polymorphus (a filamentous glider). Although this model has not been verified experimentally, M. xanthus seems to be the ideal organism with which to test it, given the genetic tools available. The second gliding motor in M. xanthus controls cell movement in groups (S-motility system). It is dependent on functional type IV pili and is operative only when cells are in close proximity to each other. Type IV pili are known to be involved in another mode of bacterial surface translocation, called twitching motility. S-motility may well represent a variation of twitching motility in M. xanthus. However, twitching differs from gliding since it involves cell movements that are jerky and abrupt and that lack the organization and smoothness observed in gliding. Components of this motor are encoded by genes of the S-system, which appear to be homologs of genes involved in the biosynthesis, assembly, and function of type IV pili in Pseudomonas aeruginosa and Neisseria gonorrhoeae. How type IV pili generate force in S-motility is currently unknown, but it is to be expected that ongoing physiological, genetic, and biochemical studies in M. xanthus, in conjunction with studies on twitching in P. aeruginosa and N. gonorrhoeae, will provide important insights into this microbial motor. The two motility systems of M. xanthus are affected to different degrees by the MglA protein, which shows similarity to a small GTPase. Bacterial chemotaxis-like sensory transduction systems control gliding motility in M. xanthus. The frz genes appear to regulate gliding movement of individual cells and movement by the S-motility system, suggesting that the two motors found in this bacterium can be regulated to result in coordinated multicellular movements. In contrast, the dif genes affect only S-system-dependent swarming.
Topics: Genes, Bacterial; Gram-Negative Bacteria; Movement; Myxococcus xanthus
PubMed: 10477310
DOI: 10.1128/MMBR.63.3.621-641.1999 -
Applied and Environmental Microbiology Jan 2020The predatory behavior of has attracted extensive attention due to its unique social traits and inherent biological activities. In addition to group hunting, individual...
The predatory behavior of has attracted extensive attention due to its unique social traits and inherent biological activities. In addition to group hunting, individual cells are able to kill and lyse prey cells; however, there is little understanding of the dynamics of solitary predation. In this study, by employing a bacterial tracking technique, we investigated predatory dynamics on at the single-cell level. The killing and lysis of by a single cell was monitored in real time by microscopic observation, and the plasmolysis of prey cells was identified at a relatively early stage of solitary predation. After quantitative characterization of their solitary predatory behavior, cells were found to respond more dramatically to direct contact with live cells than heat-killed or UV-killed cells, showing slower predator motion and faster lysing of prey. Among the three contact-dependent killing modes classified according to the major subareas of cells in contact with prey, leading pole contact was observed most. After killing the prey, approximately 72% of cells were found to leave without thorough degradation of the lysed prey, and this postresidence behavior is described as a lysis-leave pattern, indicating that solitary predation has low efficiency in terms of prey-cell consumption. Our results provide a detailed description of the single-cell level dynamics of solitary predation from both prey and predator perspectives. Bacterial predation plays multiple essential roles in bacterial selection and mortality within microbial ecosystems. In addition to its ecological and evolutionary importance, many potential applications of bacterial predation have been proposed. The myxobacterium is a well-known predatory member of the soil microbial community. Its predation is commonly considered a collective behavior comparable to a wolf pack attack; however, individual cells are also able to competently lead to the lysis of a prey cell. Using a bacterial tracking technique, we are able to observe and analyze solitary predation by on at the single-cell level and reveal the dynamics of both predator and prey during the process. The present study will not only provide a comprehensive understanding of solitary predation but also help to explain why often displays multicellular characteristic predatory behaviors in nature, while a single cell is capable of predation.
Topics: Escherichia coli; Food Chain; Myxococcus xanthus; Single-Cell Analysis
PubMed: 31704687
DOI: 10.1128/AEM.02286-19