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ArXiv Aug 2023Colonies of the social bacterium go through a morphological transition from a thin colony of cells to three-dimensional droplet-like fruiting bodies as a strategy to...
Colonies of the social bacterium go through a morphological transition from a thin colony of cells to three-dimensional droplet-like fruiting bodies as a strategy to survive starvation. The biological pathways that control the decision to form a fruiting body have been studied extensively. However, the mechanical events that trigger the creation of multiple cell layers and give rise to droplet formation remain poorly understood. By measuring cell orientation, velocity, polarity, and force with cell-scale resolution, we reveal a stochastic local polar order in addition to the more obvious nematic order. Average cell velocity and active force at topological defects agree with predictions from active nematic theory, but their fluctuations are anomalously large due to polar active forces generated by the self-propelled rod-shaped cells. We find that M. xanthus cells adjust their reversal frequency to tune the magnitude of this local polar order, which in turn controls the mechanical stresses and triggers layer formation in the colonies.
PubMed: 37576128
DOI: No ID Found -
IScience Jul 2023Many microbial phenotypes are density-dependent, including group-level phenotypes emerging from cooperation. However, surveys for the presence of a particular form of...
Many microbial phenotypes are density-dependent, including group-level phenotypes emerging from cooperation. However, surveys for the presence of a particular form of density dependence across diverse species are rare, as are direct tests for the Allee effect, i.e., positive density dependence of fitness. Here, we test for density-dependent growth under acid stress in five diverse bacterial species and find the Allee effect in all. Yet social protection from acid stress appears to have evolved by multiple mechanisms. In a strong Allee effect is mediated by pH-regulated secretion of a diffusible molecule by high-density populations. In other species, growth from low density under acid stress was not enhanced by high-density supernatant. In , high cell density may promote predation on other microbes that metabolically acidify their environment, and acid-mediated density dependence may impact the evolution of fruiting-body development. More broadly, high density may protect most bacterial species against acid stress.
PubMed: 37332671
DOI: 10.1016/j.isci.2023.106952 -
BioRxiv : the Preprint Server For... Jul 2023Type IV pili (T4P) are ubiquitous bacterial cell surface filaments important for surface motility, adhesion to biotic and abiotic surfaces, DNA uptake, biofilm...
Type IV pili (T4P) are ubiquitous bacterial cell surface filaments important for surface motility, adhesion to biotic and abiotic surfaces, DNA uptake, biofilm formation, and virulence. T4P are built from thousands of copies of the major pilin subunit and tipped by a complex composed of minor pilins and in some systems also the PilY1 adhesin. While the major pilins of structurally characterized T4P have lengths of up to 161 residues, the major pilin PilA of is unusually large with 208 residues. All major pilins have a highly conserved N-terminal domain and a highly variable C-terminal domain, and the additional residues in the PilA are due to a larger C-terminal domain. We solved the structure of the T4P (T4P ) at a resolution of 3.0 Å using cryo-electron microscopy (cryo-EM). The T4P follows the structural blueprint observed in other T4P with the pilus core comprised of the extensively interacting N-terminal α1-helices while the globular domains decorate the T4P surface. The atomic model of PilA built into this map shows that the large C-terminal domain has much more extensive intersubunit contacts than major pilins in other T4P. As expected from these greater contacts, the bending and axial stiffness of the T4P is significantly higher than that of other T4P and supports T4P-dependent motility on surfaces of different stiffnesses. Notably, T4P variants with interrupted intersubunit interfaces had decreased bending stiffness and strongly reduced motility on all surfaces. These observations support an evolutionary scenario whereby the large major pilin enables the formation of a rigid T4P that expands the environmental conditions in which the T4P system functions.
PubMed: 37503255
DOI: 10.1101/2023.07.22.550172 -
STAR Protocols Dec 2023Protein-protein interactions are foundational for many cellular processes. Such interactions are especially challenging to identify if they are transient or depend on...
Protein-protein interactions are foundational for many cellular processes. Such interactions are especially challenging to identify if they are transient or depend on environmental conditions. This protocol details steps to identify stable and transient protein interactomes in the bacterium Myxococcus xanthus using biotin ligase miniTurbo-based proximity labeling. We include instructions for optimizing the expression of control proteins, in vivo biotin labeling of bacteria grown on a surface or in suspension culture, enrichment of biotinylated proteins, and sample processing for proteomic analysis. For complete details on the use and execution of this protocol, please refer to Branon et al. (2018)..
Topics: Biotin; Myxococcus xanthus; Proteomics
PubMed: 37883223
DOI: 10.1016/j.xpro.2023.102657 -
ACS Chemical Biology Oct 2023Myxobacteria exhibit a substantial capacity to produce bioactive natural products. The biosynthetic potential of ribosomally synthesized and post-translationally...
Myxobacteria exhibit a substantial capacity to produce bioactive natural products. The biosynthetic potential of ribosomally synthesized and post-translationally modified peptides (RiPPs) from myxobacteria remains largely underexplored. In our study, we identified a novel lanthipeptide-like biosynthetic pathway, from sp. MCy9171, which was reconstituted in and proteolysis. Structural elucidation demonstrated that a series of dehydroamino acids were installed by an orphan McyB dehydratase onto the five McyA core peptides, named myxopeptins. Interestingly, compared with the canonical biosynthetic machinery of class I lanthipeptides, neither Cys residues existed in the diverse core regions, nor any LanC cyclase homologue was encoded in the pathway. Thus, we propose myxopeptins as members of a new subclass of RiPPs, named lanthipeptide-derived linear dehydroamino acid-containing peptides (LDPs), which contain dehydrated amino acids as the class-defining post-translational modifications. Furthermore, sequence similarity network (SSN) analysis revealed the wide distribution of the biosynthetic potential of LDPs in various microbial phyla, implying a co-evolutionary scenario between the precursor peptide and class I lanthipeptide biosynthetic enzymes.
Topics: Myxococcus; Escherichia coli; Peptides; Protein Processing, Post-Translational
PubMed: 37703191
DOI: 10.1021/acschembio.3c00265 -
Frontiers in Microbiology 2024Fire blight, caused by the Gram-negative bacterium , poses a substantial threat to pome fruit production worldwide. Despite existing control strategies, a pressing need...
Fire blight, caused by the Gram-negative bacterium , poses a substantial threat to pome fruit production worldwide. Despite existing control strategies, a pressing need remains for sustainable and environmentally friendly fire blight management. Myxobacteria, renowned for their predatory behavior and potent enzymes, emerge as a groundbreaking biocontrol approach with significant potential. Here, we report the biocontrol potential of a novel WCH05, against . Using various and planta assays, we demonstrated the multifaceted biocontrol abilities of strain WCH05. In plate predation assays, strain WCH05 exhibited not only strong predation against but also broad-spectrum activities against other plant pathogenic bacteria. Pre-treatment with strain WCH05 significantly decreased pear blossom blight incidence in detached inflorescence assays, achieving a controlled efficacy of 76.02% that rivaled the antibiotic streptomycin (79.79%). In greenhouse trials, strain WCH05 effectively reduced the wilting rate and disease index in young pear seedlings, exhibiting both protective (73.68%) and curative (68.66%) control. Further investigation revealed that the biocontrol activity of strain WCH05 relies on both direct contact and extracellular enzyme secretion. While cell extracts lacked inhibitory activity, ammonium sulfate-precipitated secreted proteins displayed potent lytic activity against . Substrate spectrum analysis identified peptidases, lipases, and glycosidases among the secreted enzymes, suggesting their potential roles in pathogen degradation and biocontrol efficacy. This study presents the first evidence of WCH05 as a biocontrol agent against fire blight. Its potent predatory abilities and enzymatic arsenal highlight its potential for sustainable disease management in pome fruit production. Future research will focus on identifying and characterizing specific lytic enzymes and optimizing strain WCH05 application strategies for field efficacy.
PubMed: 38650871
DOI: 10.3389/fmicb.2024.1378288 -
Microbiology Spectrum Aug 2023Myxobacteria serve as a treasure trove of secondary metabolites. During our ongoing search for bioactive natural products, a novel subclass of disorazoles termed...
Myxobacteria serve as a treasure trove of secondary metabolites. During our ongoing search for bioactive natural products, a novel subclass of disorazoles termed disorazole Z was discovered. Ten disorazole Z family members were purified from a large-scale fermentation of the myxobacterium Sorangium cellulosum So ce1875 and characterized by electrospray ionization-high-resolution mass spectrometry (ESI-HRMS), X-ray, nuclear magnetic resonance (NMR), and Mosher ester analysis. Disorazole Z compounds are characterized by the lack of one polyketide extension cycle, resulting in a shortened monomer in comparison to disorazole A, which finally forms a dimer in the bis-lactone core structure. In addition, an unprecedented modification of a geminal dimethyl group takes place to form a carboxylic acid methyl ester. The main component disorazole Z1 shows comparable activity in effectively killing cancer cells to disorazole A1 via binding to tubulin, which we show induces microtubule depolymerization, endoplasmic reticulum delocalization, and eventually apoptosis. The disorazole Z biosynthetic gene cluster (BGC) was identified and characterized from the alternative producer So ce427 and compared to the known disorazole A BGC, followed by heterologous expression in the host Myxococcus xanthus DK1622. Pathway engineering by promoter substitution and gene deletion paves the way for detailed biosynthesis studies and efficient heterologous production of disorazole Z congeners. Microbial secondary metabolites are a prolific reservoir for the discovery of bioactive compounds, which prove to be privileged scaffolds for the development of new drugs such as antibacterial and small-molecule anticancer drugs. Consequently, the continuous discovery of novel bioactive natural products is of great importance for pharmaceutical research. Myxobacteria, especially spp., which are known for their large genomes with yet-underexploited biosynthetic potential, are proficient producers of such secondary metabolites. From the fermentation broth of Sorangium cellulosum strain So ce1875, we isolated and characterized a family of natural products named disorazole Z, which showed potent anticancer activity. Further, we report on the biosynthesis and heterologous production of disorazole Z. These results can be stepping stones toward pharmaceutical development of the disorazole family of anticancer natural products for (pre)clinical studies.
Topics: Biological Products; Antineoplastic Agents; Lactones; Myxococcales
PubMed: 37318329
DOI: 10.1128/spectrum.00730-23 -
Synthetic and Systems Biotechnology Sep 2024The chromosomal position effect can significantly affect the transgene expression, which may provide an efficient strategy for the inauguration of alien genes in new...
The chromosomal position effect can significantly affect the transgene expression, which may provide an efficient strategy for the inauguration of alien genes in new hosts, but has been less explored rationally. The bacterium harbors a large circular high-GC genome, and the position effect in this chassis may result in a thousand-fold expression variation of alien natural products. In this study, we conducted transposon insertion at TA sites on the genome, and used enrichment and dilution indexes to respectively appraise high and low expression potentials of alien genes at insertion sites. The enrichment sites are characteristically distributed along the genome, and the dilution sites are overlapped well with the horizontal transfer genes. We experimentally demonstrated the enrichment sites as high expression integration sites (HEISs), and the dilution sites unsuitable for gene integration expression. This work highlights that HEISs are the plug-and-play sites for efficient expression of integrated genes.
PubMed: 38680947
DOI: 10.1016/j.synbio.2024.04.007 -
Proceedings of the National Academy of... May 2024Protein capsids are a widespread form of compartmentalization in nature. Icosahedral symmetry is ubiquitous in capsids derived from spherical viruses, as this geometry...
Protein capsids are a widespread form of compartmentalization in nature. Icosahedral symmetry is ubiquitous in capsids derived from spherical viruses, as this geometry maximizes the internal volume that can be enclosed within. Despite the strong preference for icosahedral symmetry, we show that simple point mutations in a virus-like capsid can drive the assembly of unique symmetry-reduced structures. Starting with the encapsulin from , a 180-mer bacterial capsid that adopts the well-studied viral HK97 fold, we use mass photometry and native charge detection mass spectrometry to identify a triple histidine point mutant that forms smaller dimorphic assemblies. Using cryoelectron microscopy, we determine the structures of a precedented 60-mer icosahedral assembly and an unexpected 36-mer tetrahedron that features significant geometric rearrangements around a new interaction surface between capsid protomers. We subsequently find that the tetrahedral assembly can be generated by triple-point mutation to various amino acids and that even a single histidine point mutation is sufficient to form tetrahedra. These findings represent a unique example of tetrahedral geometry when surveying all characterized encapsulins, HK97-like capsids, or indeed any virus-derived capsids reported in the Protein Data Bank, revealing the surprising plasticity of capsid self-assembly that can be accessed through minimal changes in the protein sequence.
Topics: Point Mutation; Capsid; Capsid Proteins; Cryoelectron Microscopy; Myxococcus xanthus; Models, Molecular
PubMed: 38722807
DOI: 10.1073/pnas.2321260121 -
A lytic transglycosylase connects bacterial focal adhesion complexes to the peptidoglycan cell wall.BioRxiv : the Preprint Server For... Apr 2024The Gram-negative bacterium glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into...
The Gram-negative bacterium glides on solid surfaces. Dynamic bacterial focal adhesion complexes (bFACs) convert proton motive force from the inner membrane into mechanical propulsion on the cell surface. It is unclear how the mechanical force transmits across the rigid peptidoglycan (PG) cell wall. Here we show that AgmT, a highly abundant lytic PG transglycosylase homologous to MltG, couples bFACs to PG. Coprecipitation assay and single-particle microscopy reveal that the gliding motors fail to connect to PG and thus are unable to assemble into bFACs in the absence of an active AgmT. Heterologous expression of MltG restores the connection between PG and bFACs and thus rescues gliding motility in the cells that lack AgmT. Our results indicate that bFACs anchor to AgmT-modified PG to transmit mechanical force across the PG cell wall.
PubMed: 38617213
DOI: 10.1101/2024.04.04.588103