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Current Biology : CB Mar 2002Many microorganisms, including myxobacteria, cyanobacteria, and flexibacteria, move by gliding. Although gliding always describes a slow surface-associated translocation... (Comparative Study)
Comparative Study
BACKGROUND
Many microorganisms, including myxobacteria, cyanobacteria, and flexibacteria, move by gliding. Although gliding always describes a slow surface-associated translocation in the direction of the cell's long axis, it can result from two very different propulsion mechanisms: social (S) motility and adventurous (A) motility. The force for S motility is generated by retraction of type 4 pili. A motility may be associated with the extrusion of slime, but evidence has been lacking, and how force might be generated has remained an enigma. Recently, nozzle-like structures were discovered in cyanobacteria from which slime emanated at the same rate at which the bacteria moved. This strongly implicates slime extrusion as a propulsion mechanism for gliding.
RESULTS
Here we show that similar but smaller nozzle-like structures are found in Myxococcus xanthus and that they are clustered at both cell poles, where one might expect propulsive organelles. Furthermore, light and electron microscopical observations show that slime is secreted in ribbons from the ends of cells. To test whether the slime propulsion hypothesis is physically reasonable, we construct a mathematical model of the slime nozzle to see if it can generate a force sufficient to propel M. xanthus at the observed velocities. The model assumes that the hydration of slime, a cationic polyelectrolyte, is the force-generating mechanism.
CONCLUSIONS
The discovery of nozzle-like organelles in various gliding bacteria suggests their role in prokaryotic gliding. Our calculations and our observations of slime trails demonstrate that slime extrusion from such nozzles can account for most of the observed properties of A motile gliding.
Topics: Cyanobacteria; Microscopy, Electron; Models, Biological; Movement; Mucus; Myxococcus; Organelles
PubMed: 11882287
DOI: 10.1016/s0960-9822(02)00716-9 -
MSphere May 2021Hsp70 proteins are among the most ubiquitous chaperones and play important roles in maintaining proteostasis and resisting environmental stress. Multiple copies of...
Hsp70 proteins are among the most ubiquitous chaperones and play important roles in maintaining proteostasis and resisting environmental stress. Multiple copies of Hsp70s are widely present in eukaryotic cells with redundant and divergent functions, but they have been less well investigated in prokaryotes. DK1622 is annotated as having many genes. In this study, we performed a bioinformatic analysis of Hsp70 proteins and investigated the functions of six genes in DK1622, including two genes that encode proteins with the conserved PRK00290 domain (MXAN_3192 and MXAN_6671) and four genes that encode proteins with the cl35085 or cd10170 domain. We found that only MXAN_3192 is essential for cell survival and heat shock induction. MXAN_3192, compared with the other genes, has a high transcriptional level, far exceeding that of any other gene, which, however, is not the reason for its essentiality. Deletion of MXAN_6671 () led to multiple deficiencies in development, social motility, and oxidative resistance, while deletion of each of the other four genes decreased sporulation and oxidative resistance. MXAN_3192 or , but not the other genes, restored the growth deficiency of the mutant. Our results demonstrated that the PRK00290 proteins play a central role in the complex cellular functions of , while the other diverse Hsp70 superfamily homologues probably evolved as helpers with some unknown specific functions. Hsp70 proteins are highly conserved chaperones that occur in all kingdoms of life. Multiple copies of Hsp70s are often present in genome-sequenced prokaryotes, especially taxa with complex life cycles, such as myxobacteria. We investigated the functions of six genes in DK1622 and demonstrated that the two Hsp70 proteins with the PRK00290 domain play a central role in complex cellular functions in , while other Hsp70 proteins probably evolved as helpers with some unknown specific functions.
Topics: Bacterial Proteins; Computational Biology; HSP72 Heat-Shock Proteins; Myxococcus xanthus; Phylogeny; Stress, Physiological; Transcription, Genetic
PubMed: 34011688
DOI: 10.1128/mSphere.00305-21 -
Nature Communications Jun 2023Cell division is spatiotemporally precisely regulated, but the underlying mechanisms are incompletely understood. In the social bacterium Myxococcus xanthus, the...
Cell division is spatiotemporally precisely regulated, but the underlying mechanisms are incompletely understood. In the social bacterium Myxococcus xanthus, the PomX/PomY/PomZ proteins form a single megadalton-sized complex that directly positions and stimulates cytokinetic ring formation by the tubulin homolog FtsZ. Here, we study the structure and mechanism of this complex in vitro and in vivo. We demonstrate that PomY forms liquid-like biomolecular condensates by phase separation, while PomX self-assembles into filaments generating a single large cellular structure. The PomX structure enriches PomY, thereby guaranteeing the formation of precisely one PomY condensate per cell through surface-assisted condensation. In vitro, PomY condensates selectively enrich FtsZ and nucleate GTP-dependent FtsZ polymerization and bundle FtsZ filaments, suggesting a cell division site positioning mechanism in which the single PomY condensate enriches FtsZ to guide FtsZ-ring formation and division. This mechanism shares features with microtubule nucleation by biomolecular condensates in eukaryotes, supporting this mechanism's ancient origin.
Topics: Tubulin; Biomolecular Condensates; Polymerization; Cell Division; Myxococcus xanthus
PubMed: 37380708
DOI: 10.1038/s41467-023-39513-2 -
Journal of Bacteriology Nov 2021Myxococcus xanthus is a bacterium that lives on surfaces as a predatory biofilm called a swarm. As a growing swarm feeds on prey and expands, it displays dynamic...
Myxococcus xanthus is a bacterium that lives on surfaces as a predatory biofilm called a swarm. As a growing swarm feeds on prey and expands, it displays dynamic multicellular patterns such as traveling waves called ripples and branching protrusions called flares. The rate at which a swarm expands across a surface, and the emergence of the coexisting patterns, are all controlled through coordinated cell movement. M. xanthus cells move using two motility systems known as adventurous (A) and social (S). Both are involved in swarm expansion and pattern formation. In this study, we describe a set of M. xanthus swarming genotype-to-phenotype associations that include both genetic and environmental perturbations. We identified new features of the swarming phenotype, recorded and measured swarm expansion using time-lapse microscopy, and compared the impact of mutations on different surfaces. These observations and analyses have increased our ability to discriminate between swarming phenotypes and provided context that allows us to identify some phenotypes as improbable outliers within the M. xanthus swarming phenome. Myxococcus xanthus grows on surfaces as a predatory biofilm called a swarm. In nature, a feeding swarm expands by moving over and consuming prey bacteria. In the laboratory, a swarm is created by spotting cell suspension onto nutrient agar in lieu of prey. The suspended cells quickly settle on the surface as the liquid is absorbed into the agar, and the new swarm then expands radially. An assay that measures the expansion rate of a swarm of mutant cells is the first, and sometimes only, measurement used to decide whether a particular mutation impacts swarm motility. We have broadened the scope of this assay by increasing the accuracy of measurements and introducing prey, resulting in new identifiable and quantifiable features that can be used to improve genotype-to-phenotype associations.
Topics: Bacterial Proteins; Bacteriological Techniques; Biofilms; Culture Media; Gene Expression Regulation, Bacterial; Movement; Mutation; Myxococcus xanthus
PubMed: 34543101
DOI: 10.1128/JB.00306-21 -
Biological Chemistry Nov 2020In bacteria, cell-surface polysaccharides fulfill important physiological functions, including interactions with the environment and other cells as well as protection... (Review)
Review
In bacteria, cell-surface polysaccharides fulfill important physiological functions, including interactions with the environment and other cells as well as protection from diverse stresses. The Gram-negative delta-proteobacterium Myxococcus xanthus is a model to study social behaviors in bacteria. M. xanthus synthesizes four cell-surface polysaccharides, i.e., exopolysaccharide (EPS), biosurfactant polysaccharide (BPS), spore coat polysaccharide, and O-antigen. Here, we describe recent progress in elucidating the three Wzx/Wzy-dependent pathways for EPS, BPS and spore coat polysaccharide biosynthesis and the ABC transporter-dependent pathway for O-antigen biosynthesis. Moreover, we describe the functions of these four cell-surface polysaccharides in the social life cycle of M. xanthus.
Topics: Cell Membrane; Myxococcus xanthus; Polysaccharides, Bacterial
PubMed: 32769218
DOI: 10.1515/hsz-2020-0217 -
FEMS Microbiology Reviews Mar 2010Myxococcus xanthus has a lifecycle characterized by several social interactions. In the presence of prey, M. xanthus is a predator forming cooperatively feeding... (Review)
Review
Myxococcus xanthus has a lifecycle characterized by several social interactions. In the presence of prey, M. xanthus is a predator forming cooperatively feeding colonies, and in the absence of nutrients, M. xanthus cells interact to form multicellular, spore-filled fruiting bodies. Formation of both cellular patterns depends on extracellular functions including the extracellular matrix and intercellular signals. Interestingly, the formation of these patterns also depends on several activities that involve direct cell-cell contacts between M. xanthus cells or direct contacts between M. xanthus cells and the substratum, suggesting that M. xanthus cells have a marked ability to distinguish self from nonself. Genome-wide analyses of the M. xanthus genome reveal a large potential for protein secretion. Myxococcus xanthus harbours all protein secretion systems required for translocation of unfolded and folded proteins across the cytoplasmic membrane and an intact type II secretion system. Moreover, M. xanthus contains 60 ATP-binding cassette transporters, two degenerate type III secretion systems, both of which lack the parts in the outer membrane and the needle structure, and an intact type VI secretion system for one-step translocation of proteins across the cell envelope. Also, analyses of the M. xanthus proteome reveal a large protein secretion potential including many proteins of unknown function.
Topics: Bacterial Proteins; Enzymes; Extracellular Matrix; Genome, Bacterial; Intercellular Signaling Peptides and Proteins; Membrane Transport Proteins; Models, Biological; Myxococcus xanthus; Protein Transport; Proteome
PubMed: 19895646
DOI: 10.1111/j.1574-6976.2009.00194.x -
Microbiology (Reading, England) Jul 2000
Review
Topics: Animals; Biological Evolution; Carrier Proteins; Dictyostelium; F-Box Proteins; Fungal Proteins; Mutation; Myxococcus; Protozoan Proteins
PubMed: 10878115
DOI: 10.1099/00221287-146-7-1505 -
BMC Genomics Nov 2021The Myxococcales are well known for their predatory and developmental social processes, and for the molecular complexity of regulation of these processes. Many species...
Transcriptomic analysis of the Myxococcus xanthus FruA regulon, and comparative developmental transcriptomic analysis of two fruiting body forming species, Myxococcus xanthus and Myxococcus stipitatus.
BACKGROUND
The Myxococcales are well known for their predatory and developmental social processes, and for the molecular complexity of regulation of these processes. Many species within this order have unusually large genomes compared to other bacteria, and their genomes have many genes that are unique to one specific sequenced species or strain. Here, we describe RNAseq based transcriptome analysis of the FruA regulon of Myxococcus xanthus and a comparative RNAseq analysis of two Myxococcus species, M. xanthus and Myxococcus stipitatus, as they respond to starvation and begin forming fruiting bodies.
RESULTS
We show that both species have large numbers of genes that are developmentally regulated, with over half the genome showing statistically significant changes in expression during development in each species. We also included a non-fruiting mutant of M. xanthus that is missing the transcriptional regulator FruA to identify the direct and indirect FruA regulon and to identify transcriptional changes that are specific to fruiting and not just the starvation response. We then identified Interpro gene ontologies and COG annotations that are significantly up- or down-regulated during development in each species. Our analyses support previous data for M. xanthus showing developmental upregulation of signal transduction genes, and downregulation of genes related to cell-cycle, translation, metabolism, and in some cases, DNA replication. Gene expression in M. stipitatus follows similar trends. Although not all specific genes show similar regulation patterns in both species, many critical developmental genes in M. xanthus have conserved expression patterns in M. stipitatus, and some groups of otherwise unstudied orthologous genes share expression patterns.
CONCLUSIONS
By identifying the FruA regulon and identifying genes that are similarly and uniquely regulated in two different species, this work provides a more complete picture of transcription during Myxococcus development. We also provide an R script to allow other scientists to mine our data for genes whose expression patterns match a user-selected gene of interest.
Topics: Amino Acid Sequence; Bacterial Proteins; Gene Expression Profiling; Gene Expression Regulation, Bacterial; Myxococcus; Myxococcus xanthus; Regulon; Transcription Factors; Transcriptome
PubMed: 34724903
DOI: 10.1186/s12864-021-08051-w -
MSystems Oct 2023Understanding the processes behind bacterial biofilm formation, maintenance, and dispersal is essential for addressing their effects on health and ecology. Within these...
Understanding the processes behind bacterial biofilm formation, maintenance, and dispersal is essential for addressing their effects on health and ecology. Within these multicellular communities, various cues can trigger differentiation into distinct cell types, allowing cells to adapt to their specific local environment. The soil bacterium forms biofilms in response to starvation, marked by cells aggregating into mounds. Some aggregates persist as spore-filled fruiting bodies, while others disperse after initial formation for unknown reasons. Here, we use a combination of cell tracking analysis and computational simulations to identify behaviors at the cellular level that contribute to aggregate dispersal. Our results suggest that cells in aggregates actively determine whether to disperse or persist and undergo a transition to sporulation based on a self-produced cue related to the aggregate size. Identifying these cues is an important step in understanding and potentially manipulating bacterial cell-fate decisions.
Topics: Spores, Bacterial; Myxococcus xanthus; Biofilms; Cell Differentiation
PubMed: 37747885
DOI: 10.1128/msystems.00425-23 -
Current Opinion in Microbiology Dec 2012Myxococcus xanthus is a model system for the study of dynamic protein localization and cell polarity in bacteria. M. xanthus cells are motile on solid surfaces enabled... (Review)
Review
Myxococcus xanthus is a model system for the study of dynamic protein localization and cell polarity in bacteria. M. xanthus cells are motile on solid surfaces enabled by two forms of motility. Motility is controlled by the Che-like Frz pathway, which is essential for fruiting body formation and differentiation. The Frz signal is mediated by a GTPase/GAP protein pair that establishes cell polarity and directs the motility systems. Pilus driven motility at the leading pole of the cell requires dynamic localization of two ATPases and the coordinated production of EPS synthesis. Gliding motility requires dynamic movement of large protein complexes, but the mechanism by which this system generates propulsive force is still an active area of investigation.
Topics: Bacterial Proteins; Cell Polarity; Chemotaxis; Locomotion; Myxococcus xanthus; Protein Transport; Signal Transduction
PubMed: 23142584
DOI: 10.1016/j.mib.2012.10.005