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PLoS Computational Biology Aug 2018Precise positioning of the cell division site is essential for the correct segregation of the genetic material into the two daughter cells. In the bacterium Myxococcus...
Precise positioning of the cell division site is essential for the correct segregation of the genetic material into the two daughter cells. In the bacterium Myxococcus xanthus, the proteins PomX and PomY form a cluster on the chromosome that performs a biased random walk to midcell and positively regulates cell division there. PomZ, an ATPase, is necessary for tethering of the cluster to the nucleoid and regulates its movement towards midcell. It has remained unclear how the cluster dynamics change when the biochemical parameters, such as the attachment rates of PomZ dimers to the nucleoid and the cluster, the ATP hydrolysis rate of PomZ or the mobility of PomZ interacting with the nucleoid and cluster, are varied. To answer these questions, we investigate a one-dimensional model that includes the nucleoid, the Pom cluster and PomZ proteins. We find that a mechanism based on the diffusive PomZ fluxes on the nucleoid into the cluster can explain the latter's midnucleoid localization for a broad parameter range. Furthermore, there is an ATP hydrolysis rate that minimizes the time the cluster needs to reach midnucleoid. If the dynamics of PomZ on the nucleoid is slow relative to the cluster's velocity, we observe oscillatory cluster movements around midnucleoid. To understand midnucleoid localization, we developed a semi-analytical approach that dissects the net movement of the cluster into its components: the difference in PomZ fluxes into the cluster from either side, the force exerted by a single PomZ dimer on the cluster and the effective friction coefficient of the cluster. Importantly, we predict that the Pom cluster oscillates around midnucleoid if the diffusivity of PomZ on the nucleoid is reduced. A similar approach to that applied here may also prove useful for cargo localization in ParABS systems.
Topics: Adenosine Triphosphatases; Bacterial Proteins; Cell Division; Cytokinesis; Cytoskeletal Proteins; Models, Theoretical; Myxococcus xanthus; Reproduction
PubMed: 30102692
DOI: 10.1371/journal.pcbi.1006358 -
Journal of Applied Microbiology Jan 2011To prepare, purify and characterize an extracellular enzyme from Myxococcus fulvus ANSM068, designated as myxobacteria aflatoxin degradation enzyme (MADE), which...
AIMS
To prepare, purify and characterize an extracellular enzyme from Myxococcus fulvus ANSM068, designated as myxobacteria aflatoxin degradation enzyme (MADE), which possesses degradation activity against aflatoxin B(1) (AFB(1) ), G(1) (AFG(1) ) and M(1) (AFM(1) ) in solution.
METHODS AND RESULTS
The culture supernatant of strain M. fulvus demonstrated high degradation ability against AFB(1) (71·89%), AFG(1) (68·13%) and AFM(1) (63·82%) after 48 h of incubation. An enzyme was purified from the supernatant of M. fulvus using ethanol precipitation and chromatography on DEAE-Sepharose and Superdex 75. An overall 166-fold purification of the enzyme with a recovery of 57% and a final specific activity of 569·44 × 10(3) U mg(-1) was obtained using the present purification protocol. The apparent molecular mass of MADE was estimated to be 32 kDa by SDS-PAGE. AFG(1) and AFM(1) were significantly degraded, by 96·96 and 95·80%, respectively, when treated with pure MADE (100 U ml(-1) ) produced by strain ANSM068. MADE exhibited the largest amount of activity at 35°C and pH 6·0, with Mg(2+) ions greatly promoting and Zn(2+) strongly inhibiting MADE activity.
CONCLUSIONS
An aflatoxin DEGRADATION ENZYME FROM BACTERIAL ISOLATES CAN EFFECTIVELY REMOVE AFLATOXIN B(1) , G(1) AND M(1) IN SOLUTION.
SIGNIFICANCE AND IMPACT OF THE STUDY
The high activity and wide temperature and pH range of MADE for the degradation of aflatoxin have promising applications in control of mycotoxins during food and feed processing.
Topics: Aflatoxin B1; Aflatoxin M1; Aflatoxins; Bacterial Proteins; Myxococcus
PubMed: 21040271
DOI: 10.1111/j.1365-2672.2010.04867.x -
Current Biology : CB Jun 1998Many bacteria glide over surfaces without the aid of flagella. Gliding is still somewhat mysterious, but recent studies show that it involves specialized secretory... (Review)
Review
Many bacteria glide over surfaces without the aid of flagella. Gliding is still somewhat mysterious, but recent studies show that it involves specialized secretory systems that assemble membrane-associated filaments, and the recognition of extracellular components that trigger movement via transmembrane transducers.
Topics: Cyanobacteria; Fimbriae, Bacterial; Flavobacterium; Myxococcus xanthus; O Antigens; Pili, Sex; Saccharomyces cerevisiae
PubMed: 9637910
DOI: 10.1016/s0960-9822(98)70264-7 -
Genomics Jan 2021To accurately identify the genes and pathways involved in the initiation of the Myxococcus xanthus multicellular developmental program, we have previously reported a...
To accurately identify the genes and pathways involved in the initiation of the Myxococcus xanthus multicellular developmental program, we have previously reported a method of growing vegetative populations as biofilms within a controllable environment. Using a modified approach to remove up to ~90% rRNAs, we report a comprehensive transcriptional analysis of the M. xanthus developmental cycle while comparing it with the vegetative biofilms grown in rich and poor nutrients. This study identified 1522 differentially regulated genes distributed within eight clusters during development. It also provided a comprehensive overview of genes expressed during a nutrient-stress response, specific development time points, and during development initiation and regulation. We identified several differentially expressed genes involved in key central metabolic pathways suggesting their role in regulating myxobacterial development. Overall, this study will prove an important resource for myxobacterial researchers to delineate the regulatory and functional pathways responsible for development from those of the general nutrient stress response.
Topics: Biofilms; Cell Division; Gene Expression Profiling; Multiplex Polymerase Chain Reaction; Myxococcus xanthus; RNA, Ribosomal; Transcriptome
PubMed: 33276008
DOI: 10.1016/j.ygeno.2020.11.030 -
PLoS Biology Jun 2020The development of multicellularity is a key evolutionary transition allowing for differentiation of physiological functions across a cell population that confers...
The development of multicellularity is a key evolutionary transition allowing for differentiation of physiological functions across a cell population that confers survival benefits; among unicellular bacteria, this can lead to complex developmental behaviors and the formation of higher-order community structures. Herein, we demonstrate that in the social δ-proteobacterium Myxococcus xanthus, the secretion of a novel biosurfactant polysaccharide (BPS) is spatially modulated within communities, mediating swarm migration as well as the formation of multicellular swarm biofilms and fruiting bodies. BPS is a type IV pilus (T4P)-inhibited acidic polymer built of randomly acetylated β-linked tetrasaccharide repeats. Both BPS and exopolysaccharide (EPS) are produced by dedicated Wzx/Wzy-dependent polysaccharide-assembly pathways distinct from that responsible for spore-coat assembly. While EPS is preferentially produced at the lower-density swarm periphery, BPS production is favored in the higher-density swarm interior; this is consistent with the former being known to stimulate T4P retraction needed for community expansion and a function for the latter in promoting initial cell dispersal. Together, these data reveal the central role of secreted polysaccharides in the intricate behaviors coordinating bacterial multicellularity.
Topics: Acetylation; Biosynthetic Pathways; Carbon-13 Magnetic Resonance Spectroscopy; Cell Membrane; Multigene Family; Myxococcus xanthus; Polysaccharides, Bacterial; Proton Magnetic Resonance Spectroscopy; Surface-Active Agents
PubMed: 32516311
DOI: 10.1371/journal.pbio.3000728 -
Nature Communications Oct 2020Type IVa pili are ubiquitous and versatile bacterial cell surface filaments that undergo cycles of extension, adhesion and retraction powered by the cell-envelope...
Type IVa pili are ubiquitous and versatile bacterial cell surface filaments that undergo cycles of extension, adhesion and retraction powered by the cell-envelope spanning type IVa pilus machine (T4aPM). The overall architecture of the T4aPM and the location of 10 conserved core proteins within this architecture have been elucidated. Here, using genetics, cell biology, proteomics and cryo-electron tomography, we demonstrate that the PilY1 protein and four minor pilins, which are widely conserved in T4aP systems, are essential for pilus extension in Myxococcus xanthus and form a complex that is an integral part of the T4aPM. Moreover, these proteins are part of the extended pilus. Our data support a model whereby the PilY1/minor pilin complex functions as a priming complex in T4aPM for pilus extension, a tip complex in the extended pilus for adhesion, and a cork for terminating retraction to maintain a priming complex for the next round of extension.
Topics: Bacterial Adhesion; Cryoelectron Microscopy; Electron Microscope Tomography; Fimbriae Proteins; Fimbriae, Bacterial; Models, Molecular; Mutation; Myxococcus xanthus; Proteomics
PubMed: 33028835
DOI: 10.1038/s41467-020-18803-z -
Environmental Microbiology Feb 2014The social soil bacterium, Myxococcus xanthus, displays a variety of complex and highly coordinated behaviours, including social motility, predatory rippling and...
The social soil bacterium, Myxococcus xanthus, displays a variety of complex and highly coordinated behaviours, including social motility, predatory rippling and fruiting body formation. Here we show that M. xanthus cells produce a network of outer membrane extensions in the form of outer membrane vesicle chains and membrane tubes that interconnect cells. We observed peritrichous display of vesicles and vesicle chains, and increased abundance in biofilms compared with planktonic cultures. By applying a range of imaging techniques, including three-dimensional (3D) focused ion beam scanning electron microscopy, we determined these structures to range between 30 and 60 nm in width and up to 5 μm in length. Purified vesicle chains consist of typical M. xanthus lipids, fucose, mannose, N-acetylglucosamine and N-acetylgalactoseamine carbohydrates and a small set of cargo protein. The protein content includes CglB and Tgl outer membrane proteins known to be transferable between cells in a contact-dependent manner. Most significantly, the 3D organization of cells within biofilms indicates that cells are connected via an extensive network of membrane extensions that may connect cells at the level of the periplasmic space. Such a network would allow the transfer of membrane proteins and other molecules between cells, and therefore could provide a mechanism for the coordination of social activities.
Topics: Bacterial Outer Membrane Proteins; Biofilms; Cell Membrane; Extracellular Matrix; Microscopy, Electron, Scanning; Myxococcus xanthus
PubMed: 23848955
DOI: 10.1111/1462-2920.12187 -
Journal of Bacteriology Nov 2015Escherichia coli RtcB exemplifies a family of GTP-dependent RNA repair/splicing enzymes that join 3'-PO4 ends to 5'-OH ends via stable RtcB-(histidinyl-N)-GMP and...
UNLABELLED
Escherichia coli RtcB exemplifies a family of GTP-dependent RNA repair/splicing enzymes that join 3'-PO4 ends to 5'-OH ends via stable RtcB-(histidinyl-N)-GMP and transient RNA3'pp5'G intermediates. E. coli RtcB also transfers GMP to a DNA 3'-PO4 end to form a stable "capped" product, DNA3'pp5'G. RtcB homologs are found in a multitude of bacterial proteomes, and many bacteria have genes encoding two or more RtcB paralogs; an extreme example is Myxococcus xanthus, which has six RtcBs. In this study, we purified, characterized, and compared the biochemical activities of three M. xanthus RtcB paralogs. We found that M. xanthus RtcB1 resembles E. coli RtcB in its ability to perform intra- and intermolecular sealing of a HORNAp substrate and capping of a DNA 3'-PO4 end. M. xanthus RtcB2 can splice HORNAp but has 5-fold-lower RNA ligase specific activity than RtcB1. In contrast, M. xanthus RtcB3 is distinctively feeble at ligating the HORNAp substrate, although it readily caps a DNA 3'-PO4 end. The novelty of M. xanthus RtcB3 is its capacity to cap DNA and RNA 5'-PO4 ends to form GppDNA and GppRNA products, respectively. As such, RtcB3 joins a growing list of enzymes (including RNA 3'-phosphate cyclase RtcA and thermophilic ATP-dependent RNA ligases) that can cap either end of a polynucleotide substrate. GppDNA formed by RtcB3 can be decapped to pDNA by the DNA repair enzyme aprataxin.
IMPORTANCE
RtcB enzymes comprise a widely distributed family of RNA 3'-PO4 ligases distinguished by their formation of 3'-GMP-capped RNAppG and/or DNAppG polynucleotides. The mechanism and biochemical repertoire of E. coli RtcB are well studied, but it is unclear whether its properties apply to the many bacteria that have genes encoding multiple RtcB paralogs. A comparison of the biochemical activities of three M. xanthus paralogs, RtcB1, RtcB2, and RtcB3, shows that not all RtcBs are created equal. The standout findings concern RtcB3, which is (i) inactive as an RNA 3'-PO4 ligase but adept at capping a DNA 3'-PO4 end and (ii) able to cap DNA and RNA 5'-PO4 ends to form GppDNA and GppRNA, respectively. The GppDNA and GppRNA capping reactions are novel nucleic acid modifications.
Topics: Amino Acid Sequence; Bacterial Proteins; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Molecular Sequence Data; Myxococcus xanthus; RNA Ligase (ATP); RNA, Bacterial
PubMed: 26350128
DOI: 10.1128/JB.00631-15 -
PloS One 2016Myxobacteria, a group of Gram-negative aerobes, belong to the class δ-proteobacteria and order Myxococcales. Unlike anaerobic δ-proteobacteria, they exhibit several...
Myxobacteria, a group of Gram-negative aerobes, belong to the class δ-proteobacteria and order Myxococcales. Unlike anaerobic δ-proteobacteria, they exhibit several unusual physiogenomic properties like gliding motility, desiccation-resistant myxospores and large genomes with high coding density. Here we report a 9.5 Mbp complete genome of Myxococcus hansupus that encodes 7,753 proteins. Phylogenomic and genome-genome distance based analysis suggest that Myxococcus hansupus is a novel member of the genus Myxococcus. Comparative genome analysis with other members of the genus Myxococcus was performed to explore their genome diversity. The variation in number of unique proteins observed across different species is suggestive of diversity at the genus level while the overrepresentation of several Pfam families indicates the extent and mode of genome expansion as compared to non-Myxococcales δ-proteobacteria.
Topics: Genome, Bacterial; Myxococcus; Phylogeny; Sequence Analysis, DNA
PubMed: 26900859
DOI: 10.1371/journal.pone.0148593 -
Nature Communications Nov 2020Starvation induces cell aggregation in the soil bacterium Myxococcus xanthus, followed by formation of fruiting bodies packed with myxospores. Sporulation in the absence...
Starvation induces cell aggregation in the soil bacterium Myxococcus xanthus, followed by formation of fruiting bodies packed with myxospores. Sporulation in the absence of fruiting bodies can be artificially induced by high concentrations of glycerol through unclear mechanisms. Here, we show that a compound (ambruticin VS-3) produced by a different myxobacterium, Sorangium cellulosum, affects the development of M. xanthus in a similar manner. Both glycerol (at millimolar levels) and ambruticin VS-3 (at nanomolar concentrations) inhibit M. xanthus fruiting body formation under starvation, and induce sporulation in the presence of nutrients. The response is mediated in M. xanthus by three hybrid histidine kinases (AskA, AskB, AskC) that form complexes interacting with two major developmental regulators (MrpC, FruA). In addition, AskB binds directly to the mrpC promoter in vitro. Thus, our work indicates that the AskABC-dependent regulatory pathway mediates the responses to ambruticin VS-3 and glycerol. We hypothesize that production of ambruticin VS-3 may allow S. sorangium to outcompete M. xanthus under both starvation and growth conditions in soil.
Topics: Bacterial Proteins; Gene Expression Regulation, Bacterial; Glycerol; Histidine Kinase; Mass Spectrometry; Myxococcales; Myxococcus xanthus; Promoter Regions, Genetic; Protein Binding; Signal Transduction; Sorangium; Spores, Bacterial; Stress, Physiological; Surface Plasmon Resonance; Transcription Factors
PubMed: 33149152
DOI: 10.1038/s41467-020-19384-7