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Science (New York, N.Y.) Jan 2022Gasdermin proteins form large membrane pores in human cells that release immune cytokines and induce lytic cell death. Gasdermin pore formation is triggered by...
Gasdermin proteins form large membrane pores in human cells that release immune cytokines and induce lytic cell death. Gasdermin pore formation is triggered by caspase-mediated cleavage during inflammasome signaling and is critical for defense against pathogens and cancer. We discovered gasdermin homologs encoded in bacteria that defended against phages and executed cell death. Structures of bacterial gasdermins revealed a conserved pore-forming domain that was stabilized in the inactive state with a buried lipid modification. Bacterial gasdermins were activated by dedicated caspase-like proteases that catalyzed site-specific cleavage and the removal of an inhibitory C-terminal peptide. Release of autoinhibition induced the assembly of large and heterogeneous pores that disrupted membrane integrity. Thus, pyroptosis is an ancient form of regulated cell death shared between bacteria and animals.
Topics: Apoptosis Regulatory Proteins; Bacteria; Bacterial Proteins; Bacteriophages; Bradyrhizobium; Cell Membrane; Crystallography, X-Ray; Cytophagaceae; Models, Molecular; Myxococcales; Peptide Fragments; Peptide Hydrolases; Protein Conformation; Protein Conformation, alpha-Helical; Protein Domains; Pyroptosis
PubMed: 35025633
DOI: 10.1126/science.abj8432 -
Environmental Microbiology Apr 2022Light-induced carotenogenesis in Myxococcus xanthus is controlled by the B -based CarH repressor and photoreceptor, and by a separate intricate pathway involving singlet...
Light-induced carotenogenesis in Myxococcus xanthus is controlled by the B -based CarH repressor and photoreceptor, and by a separate intricate pathway involving singlet oxygen, the B -independent CarH paralogue CarA and various other proteins, some eukaryotic-like. Whether other myxobacteria conserve these pathways and undergo photoregulated carotenogenesis is unknown. Here, comparative analyses across 27 Myxococcales genomes identified carotenogenic genes, albeit arranged differently, with carH often in their genomic vicinity, in all three Myxococcales suborders. However, CarA and its associated factors were found exclusively in suborder Cystobacterineae, with carA-carH invariably in tandem in a syntenic carotenogenic operon, except for Cystobacter/Melittangium, which lack CarA but retain all other factors. We experimentally show B -mediated photoregulated carotenogenesis in representative myxobacteria, and a remarkably plastic CarH operator design and DNA binding across Myxococcales. Unlike the two characterized CarH from other phyla, which are tetrameric, Cystobacter CarH (the first myxobacterial homologue amenable to analysis in vitro) is a dimer that combines direct CarH-like B -based photoregulation with CarA-like DNA binding and inhibition by an antirepressor. This study provides new molecular insights into B -dependent photoreceptors. It further establishes the B -dependent pathway for photoregulated carotenogenesis as broadly prevalent across myxobacteria and its evolution, exclusively in one suborder, into a parallel complex B -independent circuit.
Topics: Bacterial Proteins; DNA; Gene Expression Regulation, Bacterial; Myxococcales; Phosphothreonine; Repressor Proteins
PubMed: 35005822
DOI: 10.1111/1462-2920.15895 -
Molecular Microbiology Jul 2016For many bacteria, motility is essential for survival, growth, virulence, biofilm formation and intra/interspecies interactions. Since natural environments differ,... (Review)
Review
For many bacteria, motility is essential for survival, growth, virulence, biofilm formation and intra/interspecies interactions. Since natural environments differ, bacteria have evolved remarkable motility systems to adapt, including swimming in aqueous media, and swarming, twitching and gliding on solid and semi-solid surfaces. Although tremendous advances have been achieved in understanding swimming and swarming motilities powered by flagella, and twitching motility powered by Type IV pili, little is known about gliding motility. Bacterial gliders are a heterogeneous group containing diverse bacteria that utilize surface motilities that do not depend on traditional flagella or pili, but are powered by mechanisms that are less well understood. Recently, advances in our understanding of the molecular machineries for several gliding bacteria revealed the roles of modified ion channels, secretion systems and unique machinery for surface movements. These novel mechanisms provide rich source materials for studying the function and evolution of complex microbial nanomachines. In this review, we summarize recent findings made on the gliding mechanisms of the myxobacteria, flavobacteria and mycoplasmas.
Topics: Cell Movement; Flavobacteriaceae; Models, Biological; Movement; Mycoplasma; Myxococcales; Secretory Pathway; Virulence
PubMed: 27028358
DOI: 10.1111/mmi.13389 -
Journal of Molecular Biology Nov 2015Prokaryotes often reside in groups where a high degree of relatedness has allowed the evolution of cooperative behaviors. However, very few bacteria or archaea have made... (Review)
Review
Prokaryotes often reside in groups where a high degree of relatedness has allowed the evolution of cooperative behaviors. However, very few bacteria or archaea have made the successful transition from unicellular to obligate multicellular life. A notable exception is the myxobacteria, in which cells cooperate to perform group functions highlighted by fruiting body development, an obligate multicellular function. Like all multicellular organisms, myxobacteria face challenges in how to organize and maintain multicellularity. These challenges include maintaining population homeostasis, carrying out tissue repair and regulating the behavior of non-cooperators. Here, we describe the major cooperative behaviors that myxobacteria use: motility, predation and development. In addition, this review emphasizes recent discoveries in the social behavior of outer membrane exchange, wherein kin share outer membrane contents. Finally, we review evidence that outer membrane exchange may be involved in regulating population homeostasis, thus serving as a social tool for myxobacteria to make the cyclic transitions from unicellular to multicellular states.
Topics: Bacterial Outer Membrane Proteins; Myxococcales
PubMed: 26254571
DOI: 10.1016/j.jmb.2015.07.022 -
Microbial Cell Factories Apr 2012Myxobacteria are amongst the top producers of natural products. The diversity and unique structural properties of their secondary metabolites is what make these social...
Myxobacteria are amongst the top producers of natural products. The diversity and unique structural properties of their secondary metabolites is what make these social microbes highly attractive for drug discovery. Screening of products derived from these bacteria has revealed a puzzling amount of hits against infectious and non-infectious human diseases. Preying mainly on other bacteria and fungi, why would these ancient hunters manufacture compounds beneficial for us? The answer may be the targeting of shared processes and structural features conserved throughout evolution.
Topics: Biological Products; Drug Discovery; Myxococcales; Spores, Bacterial
PubMed: 22545867
DOI: 10.1186/1475-2859-11-52 -
Microbiology (Reading, England) Jul 2023Myxobacteria are social microbial predators that use cell-cell contacts to identify bacterial or fungal prey and to differentiate kin relatives to initiate cellular... (Review)
Review
Myxobacteria are social microbial predators that use cell-cell contacts to identify bacterial or fungal prey and to differentiate kin relatives to initiate cellular responses. For prey killing, they assemble Tad-like and type III-like secretion systems at contact sites. For kin discrimination (KD), they assemble outer membrane exchange complexes composed of the TraA and TraB receptors at contacts sites. A type VI secretion system and Rhs proteins also mediate KD. Following cellular recognition, these systems deliver appropriate effectors into target cells. For prey, this leads to cell death and lysis for nutrient consumption by myxobacteria. In KD, a panel of effectors are delivered, and if adjacent cells are clonal cells, resistance ensues because they express a cognate panel of immunity factors; while nonkin lack complete immunity and are intoxicated. This review compares and contrasts recent findings from these systems in myxobacteria.
Topics: Animals; Myxococcales; Predatory Behavior; Myxococcus xanthus; Bacterial Proteins
PubMed: 37494115
DOI: 10.1099/mic.0.001372 -
Applied and Environmental Microbiology Aug 2020Biological nitrogen fixation is an essential reaction in a major pathway for supplying nitrogen to terrestrial environments. Previous culture-independent analyses based...
Biological nitrogen fixation is an essential reaction in a major pathway for supplying nitrogen to terrestrial environments. Previous culture-independent analyses based on soil DNA/RNA/protein sequencing could globally detect the nitrogenase genes/proteins of (in the class ), commonly distributed in soil environments and predominant in paddy soils; this suggests the importance of in nitrogen fixation in soil environments. However, direct experimental evidence is lacking; there has been no research on the genetic background and ability of to fix nitrogen. Therefore, we verified the diazotrophy of based on both genomic and culture-dependent analyses using sp. strains PSR-1 and Red267 isolated from soils. Based on the comparison of gene clusters, strains PSR-1 and Red267 as well as strains Fw109-5, K, and diazotrophic and in the class contain the minimum set of genes for nitrogenase (). These results imply that species have the ability to fix nitrogen. In fact, PSR-1 and Red267 exhibited N-dependent growth and acetylene reduction activity (ARA) Transcriptional activity of the gene was also detected when both strains were cultured with N gas as a sole nitrogen source, indicating that can fix and assimilate N gas by nitrogenase. In addition, PSR-1- or Red267-inoculated soil showed ARA activity and the growth of the inoculated strains on the basis of RNA-based analysis, demonstrating that can fix nitrogen in the paddy soil environment. Our study provides novel insights into the pivotal environmental function, i.e., nitrogen fixation, of , which is a common soil bacterium. is globally distributed in soil environments, especially predominant in paddy soils. Current studies based on environmental DNA/RNA analyses frequently detect gene fragments encoding nitrogenase of from various soil environments. Although the importance of as a diazotroph in nature has been suggested by culture-independent studies, there has been no solid evidence and validation from genomic and culture-based analyses that fixes nitrogen. This study demonstrates that harboring nitrogenase genes exhibits diazotrophic ability; moreover, N-dependent growth was demonstrated and in the soil environment. Our findings indicate that nitrogen fixation is important for to survive under nitrogen-deficient environments and provide a novel insight into the environmental function of , which is a common bacterium in soils.
Topics: Myxococcales; Nitrogen Cycle; Nitrogen Fixation; Soil Microbiology
PubMed: 32532868
DOI: 10.1128/AEM.00956-20 -
Genes Mar 2023Social diversification in microbes is an evolutionary process where lineages bifurcate into distinct populations that cooperate with themselves but not with other... (Review)
Review
Social diversification in microbes is an evolutionary process where lineages bifurcate into distinct populations that cooperate with themselves but not with other groups. In bacteria, this is frequently driven by horizontal transfer of mobile genetic elements (MGEs). Here, the resulting acquisition of new genes changes the recipient's social traits and consequently how they interact with kin. These changes include discriminating behaviors mediated by newly acquired effectors. Since the producing cell is protected by cognate immunity factors, these selfish elements benefit from selective discrimination against recent ancestors, thus facilitating their proliferation and benefiting the host. Whether social diversification benefits the population at large is less obvious. The widespread use of next-generation sequencing has recently provided new insights into population dynamics in natural habitats and the roles MGEs play. MGEs belong to accessory genomes, which often constitute the majority of the pangenome of a taxon, and contain most of the kin-discriminating loci that fuel rapid social diversification. We further discuss mechanisms of diversification and its consequences to populations and conclude with a case study involving myxobacteria.
Topics: Bacteria; Myxococcales; Biological Evolution; Genome; Interspersed Repetitive Sequences
PubMed: 36980919
DOI: 10.3390/genes14030648 -
Marine Drugs Jun 2018Currently considered an excellent candidate source of novel chemical diversity, the existence of marine myxobacteria was in question less than 20 years ago. This review... (Review)
Review
Currently considered an excellent candidate source of novel chemical diversity, the existence of marine myxobacteria was in question less than 20 years ago. This review aims to serve as a roll call for marine myxobacteria and to summarize their unique features when compared to better-known terrestrial myxobacteria. Characteristics for discrimination between obligate halophilic, marine myxobacteria and halotolerant, terrestrial myxobacteria are discussed. The review concludes by highlighting the need for continued discovery and exploration of marine myxobacteria as producers of novel natural products.
Topics: Biological Products; Molecular Structure; Myxococcales; Phylogeny; Salt Tolerance; Seawater
PubMed: 29899205
DOI: 10.3390/md16060209 -
Marine Drugs Sep 2018Prior to 2005, the vast majority of characterized myxobacteria were obtained from terrestrial habitats. Since then, several species of halotolerant and even obligate... (Review)
Review
Prior to 2005, the vast majority of characterized myxobacteria were obtained from terrestrial habitats. Since then, several species of halotolerant and even obligate marine myxobacteria have been described. Chemical analyses of extracts from these organisms have confirmed their ability to produce secondary metabolites with unique chemical scaffolds. Indeed, new genera of marine-derived myxobacteria, particularly , have been shown to produce novel chemical scaffolds that differ from those observed in soil myxobacteria. Further studies have shown that marine sponges and terrestrial myxobacteria are capable of producing similar or even identical secondary metabolites, suggesting that myxobacterial symbionts may have been the true producers. Recent in silico analysis of the genome sequences available from six marine myxobacteria disclosed a remarkably versatile biosynthetic potential. With access to ever-advancing tools for small molecule and genetic evaluation, these studies suggest a bright future for expeditions into this yet untapped resource for secondary metabolites.
Topics: Animals; Aquatic Organisms; Biodiversity; Biological Products; Biosynthetic Pathways; Computer Simulation; Genome, Bacterial; Myxococcales; Phylogeny; Porifera; Soil Microbiology; Symbiosis
PubMed: 30189599
DOI: 10.3390/md16090314