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Microbial Physiology 2021Predatory bacteria gained interest in the last 20 years. Nevertheless, only a few species are well characterized. The endobiotic predator Bdellovibrio bacteriovorus... (Review)
Review
Predatory bacteria gained interest in the last 20 years. Nevertheless, only a few species are well characterized. The endobiotic predator Bdellovibrio bacteriovorus invades its prey to consume it from the inside, whereas Myxococcus xanthus hunts as a whole group to overcome its prey. Both species were described to prey on cyanobacteria as well. This minireview summarizes the findings of the last 20 years of predatory bacteria of cyanobacteria and is supplemented by new findings from a screening experiment for bacterial predators of the model organism Anabaena variabilis PCC 7937. Known predatory bacteria of cyanobacteria belong to the phyla Proteobacteria, Bacteroidetes, and Firmicutes and follow different hunting strategies. The underlying mechanisms are in most cases not known in much detail. Isolates from the screening experiment were clustered after predation behaviour and analyzed with respect to their size. The effect of predation in high nitrate levels and the occurrence of nitrogen-fixing cells, called heterocysts, are addressed.
Topics: Animals; Bdellovibrio bacteriovorus; Cyanobacteria; Myxococcus xanthus; Predatory Behavior
PubMed: 34010833
DOI: 10.1159/000516427 -
Viruses Jul 2018Bacteriophages have been used as molecular tools in fundamental biology investigations for decades. Beyond this, however, they play a crucial role in the... (Review)
Review
Bacteriophages have been used as molecular tools in fundamental biology investigations for decades. Beyond this, however, they play a crucial role in the eco-evolutionary dynamics of bacterial communities through their demographic impact and the source of genetic information they represent. The increasing interest in describing ecological and evolutionary aspects of bacteria⁻phage interactions has led to major insights into their fundamental characteristics, including arms race dynamics and acquired bacterial immunity. Here, we review knowledge on the phages of the myxobacteria with a major focus on phages infecting , a bacterial model system widely used to study developmental biology and social evolution. In particular, we focus upon the isolation of myxophages from natural sources and describe the morphology and life cycle parameters, as well as the molecular genetics and genomics of the major groups of myxophages. Finally, we propose several interesting research directions which focus on the interplay between myxobacterial host sociality and bacteria⁻phage interactions.
Topics: Bacteriophages; Evolution, Molecular; Gene Expression Regulation, Bacterial; Genome, Viral; Myxococcus xanthus; Sewage; Soil Microbiology
PubMed: 30021959
DOI: 10.3390/v10070374 -
Current Biology : CB Feb 2014Many bacteria glide smoothly on surfaces, despite having no discernable propulsive organelles on their surface. Recent experiments with Myxococcus xanthus and... (Review)
Review
Many bacteria glide smoothly on surfaces, despite having no discernable propulsive organelles on their surface. Recent experiments with Myxococcus xanthus and Flavobacterium johnsoniae show that both of these distantly related bacterial species glide using proteins that move in helical tracks, albeit with significantly different motility mechanisms. Both species utilize proton-motive force for movement. Although the motors that power gliding in M. xanthus have been identified, the F. johnsoniae motors remain to be discovered.
Topics: Bacterial Proteins; Biological Transport; Cell Membrane; Flavobacterium; Myxococcus xanthus
PubMed: 24556443
DOI: 10.1016/j.cub.2013.12.034 -
Microbiology (Reading, England) Jan 2016Myxococcus xanthus is a predatory bacterium and a model system for social behaviour in bacteria. Myx. xanthus forms thin biofilms, where cells work together to colonize... (Review)
Review
Myxococcus xanthus is a predatory bacterium and a model system for social behaviour in bacteria. Myx. xanthus forms thin biofilms, where cells work together to colonize new territory, invade prey colonies and lyse prey cells. Prey-cell lysis occurs at close proximity, and utilizes antibiotics such as myxovirescin, hydrolytic enzymes such as the protease MepA and extracellular outer-membrane vesicles that may facilitate delivery. Many questions about the mechanism of prey lysis remain, as well as a complete understanding of the vast hydrolytic and secondary metabolite potential present in the Myx. xanthus genome. However, it is clear that predation presents unique challenges for this bacterium, which are solved, in part, through the social behaviours at the disposal of Myx. xanthus. Here, we discuss the life cycle of Myx. xanthus, and the hypothesis that multicellular behaviour in this organism is critical to, and derives from, the challenges of growth as a bacterial predator.
Topics: Bacterial Proteins; Myxococcus xanthus; Spores, Fungal
PubMed: 26518442
DOI: 10.1099/mic.0.000208 -
Journal of Bacteriology Sep 2023The regulation of biofilm and motile states as alternate bacterial lifestyles has been studied extensively in flagellated bacteria, where the second messenger...
The regulation of biofilm and motile states as alternate bacterial lifestyles has been studied extensively in flagellated bacteria, where the second messenger cyclic-di-GMP (cdG) plays a crucial role. However, much less is known about the mechanisms of such regulation in motile bacteria without flagella. The bacterial type IV pilus (T4P) serves as a motility apparatus that enables to move on solid surfaces. PilB, the T4P assembly ATPase, is, therefore, required for T4P-dependent motility in . Interestingly, T4P is also involved in the regulation of exopolysaccharide as the biofilm matrix material in this bacterium. A newly discovered cdG-binding domain, MshE, is conserved in the N-terminus of PilB (PilB) in and other bacteria. This suggests that cdG may bind to PilB to control the respective outputs that regulate biofilm development and T4P-powered motility. In this study, we aimed to validate PilB as a cdG effector protein. We performed a systematic mutational analysis of its cdG-binding domain to investigate its relationship with motility, piliation, and biofilm formation. Excluding those resulting in low levels of PilB protein, all other substitution mutations in PilB resulted in mutants with distinct and differential phenotypes in piliation and biofilm levels in . This suggests that the PilB domain plays dual roles in modulating motility and biofilm levels, and these two functions of PilB can be dependent on and independent of each other in . IMPORTANCE The regulation of motility and biofilm by cyclic-di-GMP in flagellated bacteria has been extensively investigated. However, our knowledge regarding this regulation in motile bacteria without flagella remains limited. Here, we aimed to address this gap by investigating a non-flagellated bacterium with motility powered by bacterial type-IV pilus (T4P). Previous studies hinted at the possibility of PilB, the T4P assembly ATPase, serving as a cyclic-di-GMP effector involved in regulating both motility and biofilm. Our findings strongly support the hypothesis that PilB directly interacts with cyclic-di-GMP to act as a potential switch to promote biofilm formation or T4P-dependent motility. These results shed light on the bifurcation of PilB functions and its pivotal role in coordinating biofilm formation and T4P-mediated motility.
Topics: Myxococcus xanthus; Cyclic GMP; Adenosine Triphosphatases; Biofilms
PubMed: 37695853
DOI: 10.1128/jb.00221-23 -
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 -
Trends in Genetics : TIG Jan 2017The bacterium Myxococcus xanthus undergoes multicellular development when starved. Thousands of cells build mounds in which some differentiate into spores. This... (Review)
Review
The bacterium Myxococcus xanthus undergoes multicellular development when starved. Thousands of cells build mounds in which some differentiate into spores. This remarkable feat and the genetic tractability of Myxococcus provide a unique opportunity to understand the evolution of gene regulatory networks (GRNs). Recent work has revealed a GRN involving interconnected cascades of signal-responsive transcriptional activators. Initially, starvation-induced intracellular signals direct changes in gene expression. Subsequently, self-generated extracellular signals provide morphological cues that regulate certain transcriptional activators. However, signals for many of the activators remain to be discovered. A key insight is that activators often work combinatorially, allowing signal integration. The Myxococcus GRN differs strikingly from those governing sporulation of Bacillus and Streptomyces, suggesting that Myxococcus evolved a highly signal-responsive GRN to enable complex multicellular development.
Topics: Gene Expression Regulation, Bacterial; Gene Regulatory Networks; Mutation; Myxococcus xanthus; Signal Transduction; Spores, Bacterial; Transcriptional Activation
PubMed: 27916428
DOI: 10.1016/j.tig.2016.10.006 -
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 -
Nature Communications Sep 2023Many species, such as fish schools or bird flocks, rely on collective motion to forage, prey, or escape predators. Likewise, Myxococcus xanthus forages and moves...
Many species, such as fish schools or bird flocks, rely on collective motion to forage, prey, or escape predators. Likewise, Myxococcus xanthus forages and moves collectively to prey and feed on other bacterial species. These activities require two distinct motility machines enabling adventurous (A) and social (S) gliding, however when and how these mechanisms are used has remained elusive. Here, we address this long-standing question by applying multiscale semantic cell tracking during predation. We show that: (1) foragers and swarms can comprise A- and S-motile cells, with single cells exchanging frequently between these groups; (2) A-motility is critical to ensure the directional movement of both foragers and swarms; (3) the combined action of A- and S-motile cells within swarms leads to increased predation efficiencies. These results challenge the notion that A- and S-motilities are exclusive to foragers and swarms, and show that these machines act synergistically to enhance predation efficiency.
Topics: Animals; Predatory Behavior; Cell Tracking; Cooperative Behavior; Motion; Myxococcus xanthus
PubMed: 37696789
DOI: 10.1038/s41467-023-41193-x -
Current Opinion in Microbiology Dec 2013In rod shaped bacteria, numerous cellular components are targeted to the cell poles, and such localization is often important for optimal function. In particular,... (Review)
Review
In rod shaped bacteria, numerous cellular components are targeted to the cell poles, and such localization is often important for optimal function. In particular, recognition of poles is often linked to division site selection, chromosome segregation, chemotactic signaling, and motility. Recent advances in understanding polarity include identification of a Vibrio cholerae protein that mediates polar localization of a chromosome origin and chemotaxis clusters, as well as a downstream protein that contributes solely to localization of chemotaxis proteins. In Caulobacter crescentus, the molecular mechanisms by which polar determinants and effectors are localized, and the key roles for nucleotide-dependent switches, have been defined. Finally, roles for, and interactions between, factors that mediate environmentally determined polarity in Myxococcus xanthus have recently been characterized.
Topics: Caulobacter crescentus; Cell Polarity; Myxococcus xanthus; Vibrio cholerae
PubMed: 24029491
DOI: 10.1016/j.mib.2013.08.006