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Acta Biochimica Polonica Sep 2020The insect immune system is responsible for maintaining the homeostasis of organisms. If the pathogen is able to breach the defensive barriers of the host, cellular and... (Review)
Review
The insect immune system is responsible for maintaining the homeostasis of organisms. If the pathogen is able to breach the defensive barriers of the host, cellular and humoral mechanisms are triggered. Initiation of effective defence response is possible thanks to pathogen-associated molecular patterns, among which peptidoglycan recognition proteins play a prominent role. They recognize pathogen-associated molecular patterns and some of them also have enzymatic activity. The main aim of peptidoglycan recognition proteins is to activate pathways regulating the synthesis of immune peptides. Some of the peptidoglycan recognition proteins are involved in the phagocytosis process, activation of the prophenoloxidase cascade, and regulation of the xenophagy process. The structural diversity and high specificity of peptidoglycan recognition proteins suggests that they can serve many previously unknown functions in insect's systemic response.
Topics: Animals; Carrier Proteins; Catechol Oxidase; Enzyme Precursors; Host-Pathogen Interactions; Immunity, Innate; Insect Proteins; Insecta; Pathogen-Associated Molecular Pattern Molecules; Peptidoglycan; Receptors, Pattern Recognition
PubMed: 32940448
DOI: 10.18388/abp.2020_5345 -
Nature Jun 2020The primary structural component of the bacterial cell wall is peptidoglycan, which is essential for viability and the synthesis of which is the target for crucial...
The primary structural component of the bacterial cell wall is peptidoglycan, which is essential for viability and the synthesis of which is the target for crucial antibiotics. Peptidoglycan is a single macromolecule made of glycan chains crosslinked by peptide side branches that surrounds the cell, acting as a constraint to internal turgor. In Gram-positive bacteria, peptidoglycan is tens of nanometres thick, generally portrayed as a homogeneous structure that provides mechanical strength. Here we applied atomic force microscopy to interrogate the morphologically distinct Staphylococcus aureus and Bacillus subtilis species, using live cells and purified peptidoglycan. The mature surface of live cells is characterized by a landscape of large (up to 60 nm in diameter), deep (up to 23 nm) pores constituting a disordered gel of peptidoglycan. The inner peptidoglycan surface, consisting of more nascent material, is much denser, with glycan strand spacing typically less than 7 nm. The inner surface architecture is location dependent; the cylinder of B. subtilis has dense circumferential orientation, while in S. aureus and division septa for both species, peptidoglycan is dense but randomly oriented. Revealing the molecular architecture of the cell envelope frames our understanding of its mechanical properties and role as the environmental interface, providing information complementary to traditional structural biology approaches.
Topics: Bacillus subtilis; Cell Wall; Microbial Viability; Microscopy, Atomic Force; Peptidoglycan; Staphylococcus aureus
PubMed: 32523118
DOI: 10.1038/s41586-020-2236-6 -
Nature Communications Nov 2022Bacterial cell shape is generally determined through an interplay between the peptidoglycan cell wall and cytoplasmic filaments made of polymerized MreB. Indeed, some...
Bacterial cell shape is generally determined through an interplay between the peptidoglycan cell wall and cytoplasmic filaments made of polymerized MreB. Indeed, some bacteria (e.g., Mycoplasma) that lack both a cell wall and mreB genes consist of non-motile cells that are spherical or pleomorphic. However, other members of the same class Mollicutes (e.g., Spiroplasma, also lacking a cell wall) display a helical cell shape and kink-based motility, which is thought to rely on the presence of five MreB isoforms and a specific fibril protein. Here, we show that heterologous expression of Spiroplasma fibril and MreB proteins confers helical shape and kinking ability to Mycoplasma capricolum cells. Isoform MreB5 is sufficient to confer helicity and kink propagation to mycoplasma cells. Cryoelectron microscopy confirms the association of cytoplasmic MreB filaments with the plasma membrane, suggesting a direct effect on membrane curvature. However, in our experiments, the heterologous expression of MreBs and fibril did not result in efficient motility in culture broth, indicating that additional, unknown Spiroplasma components are required for swimming.
Topics: Cryoelectron Microscopy; Bacterial Proteins; Cytoskeleton; Peptidoglycan; Spiroplasma
PubMed: 36376306
DOI: 10.1038/s41467-022-34478-0 -
Advanced Science (Weinheim,... May 2022Water-responsive (WR) materials that reversibly deform in response to humidity changes show great potential for developing muscle-like actuators for miniature and...
Water-responsive (WR) materials that reversibly deform in response to humidity changes show great potential for developing muscle-like actuators for miniature and biomimetic robotics. Here, it is presented that Bacillus (B.) subtilis' peptidoglycan (PG) exhibits WR actuation energy and power densities reaching 72.6 MJ m and 9.1 MW m , respectively, orders of magnitude higher than those of frequently used actuators, such as piezoelectric actuators and dielectric elastomers. PG can deform as much as 27.2% within 110 ms, and its actuation pressure reaches ≈354.6 MPa. Surprisingly, PG exhibits an energy conversion efficiency of ≈66.8%, which can be attributed to its super-viscous nanoconfined water that efficiently translates the movement of water molecules to PG's mechanical deformation. Using PG, WR composites that can be integrated into a range of engineering structures are developed, including a robotic gripper and linear actuators, which illustrate the possibilities of using PG as building blocks for high-efficiency WR actuators.
Topics: Elastomers; Muscles; Peptidoglycan; Robotics; Water
PubMed: 35285168
DOI: 10.1002/advs.202104697 -
Microbial Genomics Jan 2024Many peptidoglycan-deficient bacteria such as the are known host-associated lineages, lacking the environmental resistance mechanisms and metabolic capabilities...
Many peptidoglycan-deficient bacteria such as the are known host-associated lineages, lacking the environmental resistance mechanisms and metabolic capabilities necessary for a free-living lifestyle. Several peptidoglycan-deficient and non-sporulating orders of interest are thought to be descended from Gram-positive sporulating through reductive evolution. Here we annotate 2650 genomes belonging to the class , according to the Genome Taxonomy Database, to predict the peptidoglycan and sporulation phenotypes of three novel orders, , and , known only through environmental sequence surveys. These lineages are interspersed between peptidoglycan-deficient non-sporulating orders including the and , and more typical Gram-positive orders such as the and . We use the extant genotypes to perform ancestral state reconstructions. The novel orders are predicted to have small genomes with minimal metabolic capabilities and to comprise a mix of peptidoglycan-deficient and/or non-sporulating species. In contrast to expectations based on cultured representatives, the order lacks many of the genes involved in peptidoglycan and endospore formation. The reconstructed evolutionary history of these traits suggests multiple independent whole-genome reductions and loss of phenotype via intermediate transition states that continue into the present. We suggest that the evolutionary history of the reduced-genome lineages within the class is one driven by multiple independent transitions to host-associated lifestyles, with the degree of reduction in environmental resistance and metabolic capabilities correlated with degree of host association.
Topics: Peptidoglycan; Mycoplasmatales; Gram-Positive Bacteria; Firmicutes; Genotype
PubMed: 38189216
DOI: 10.1099/mgen.0.001176 -
PLoS Genetics Apr 2023Commensal microbes in animals have a profound impact on tissue homeostasis, stress resistance, and ageing. We previously showed in Drosophila melanogaster that...
Commensal microbes in animals have a profound impact on tissue homeostasis, stress resistance, and ageing. We previously showed in Drosophila melanogaster that Acetobacter persici is a member of the gut microbiota that promotes ageing and shortens fly lifespan. However, the molecular mechanism by which this specific bacterial species changes lifespan and physiology remains unclear. The difficulty in studying longevity using gnotobiotic flies is the high risk of contamination during ageing. To overcome this technical challenge, we used a bacteria-conditioned diet enriched with bacterial products and cell wall components. Here, we demonstrate that an A. persici-conditioned diet shortens lifespan and increases intestinal stem cell (ISC) proliferation. Feeding adult flies a diet conditioned with A. persici, but not with Lactiplantibacillus plantarum, can decrease lifespan but increase resistance to paraquat or oral infection of Pseudomonas entomophila, indicating that the bacterium alters the trade-off between lifespan and host defence. A transcriptomic analysis using fly intestine revealed that A. persici preferably induces antimicrobial peptides (AMPs), while L. plantarum upregulates amidase peptidoglycan recognition proteins (PGRPs). The specific induction of these Imd target genes by peptidoglycans from two bacterial species is due to the stimulation of the receptor PGRP-LC in the anterior midgut for AMPs or PGRP-LE from the posterior midgut for amidase PGRPs. Heat-killed A. persici also shortens lifespan and increases ISC proliferation via PGRP-LC, but it is not sufficient to alter the stress resistance. Our study emphasizes the significance of peptidoglycan specificity in determining the gut bacterial impact on healthspan. It also unveils the postbiotic effect of specific gut bacterial species, which turns flies into a "live fast, die young" lifestyle.
Topics: Animals; Drosophila; Drosophila melanogaster; Longevity; Peptidoglycan; Bacteria; Homeostasis; Amidohydrolases
PubMed: 37023169
DOI: 10.1371/journal.pgen.1010709 -
Protein Science : a Publication of the... Dec 2019Bacteria are surrounded by a complex cell envelope made up of one or two membranes supplemented with a layer of peptidoglycan (PG). The envelope is responsible for the... (Review)
Review
Bacteria are surrounded by a complex cell envelope made up of one or two membranes supplemented with a layer of peptidoglycan (PG). The envelope is responsible for the protection of bacteria against lysis in their oft-unpredictable environments and it contributes to cell integrity, morphology, signaling, nutrient/small-molecule transport, and, in the case of pathogenic bacteria, host-pathogen interactions and virulence. The cell envelope requires considerable remodeling during cell division in order to produce genetically identical progeny. Several proteinaceous machines are responsible for the homeostasis of the cell envelope and their activities must be kept coordinated in order to ensure the remodeling of the envelope is temporally and spatially regulated correctly during multiple cycles of cell division and growth. This review aims to highlight the complexity of the components of the cell envelope, but focusses specifically on the molecular apparatuses involved in the synthesis of the PG wall, and the degree of cross talk necessary between the cell division and the cell wall remodeling machineries to coordinate PG remodeling during division. The current understanding of many of the proteins discussed here has relied on structural studies, and this review concentrates particularly on this structural work.
Topics: Bacteria; Carbohydrate Conformation; Cell Division; Cell Membrane; Models, Molecular; Peptidoglycan
PubMed: 31495975
DOI: 10.1002/pro.3722 -
PLoS Pathogens Mar 2021Peptidoglycan is the major structural component of the Staphylococcus aureus cell wall, in which it maintains cellular integrity, is the interface with the host, and its...
Peptidoglycan is the major structural component of the Staphylococcus aureus cell wall, in which it maintains cellular integrity, is the interface with the host, and its synthesis is targeted by some of the most crucial antibiotics developed. Despite this importance, and the wealth of data from in vitro studies, we do not understand the structure and dynamics of peptidoglycan during infection. In this study we have developed methods to harvest bacteria from an active infection in order to purify cell walls for biochemical analysis ex vivo. Isolated ex vivo bacterial cells are smaller than those actively growing in vitro, with thickened cell walls and reduced peptidoglycan crosslinking, similar to that of stationary phase cells. These features suggested a role for specific peptidoglycan homeostatic mechanisms in disease. As S. aureus missing penicillin binding protein 4 (PBP4) has reduced peptidoglycan crosslinking in vitro its role during infection was established. Loss of PBP4 resulted in an increased recovery of S. aureus from the livers of infected mice, which coincided with enhanced fitness within murine and human macrophages. Thicker cell walls correlate with reduced activity of peptidoglycan hydrolases. S. aureus has a family of 4 putative glucosaminidases, that are collectively crucial for growth. Loss of the major enzyme SagB, led to attenuation during murine infection and reduced survival in human macrophages. However, loss of the other three enzymes Atl, SagA and ScaH resulted in clustering dependent attenuation, in a zebrafish embryo, but not a murine, model of infection. A combination of pbp4 and sagB deficiencies resulted in a restoration of parental virulence. Our results, demonstrate the importance of appropriate cell wall structure and dynamics during pathogenesis, providing new insight to the mechanisms of disease.
Topics: Animals; Cell Wall; Host-Pathogen Interactions; Mice; Peptidoglycan; Staphylococcal Infections; Staphylococcus aureus; Virulence; Zebrafish
PubMed: 33788901
DOI: 10.1371/journal.ppat.1009468 -
Journal of Industrial Microbiology &... Apr 2021This study evaluates peptidoglycan hydrolysis by a microbial muramidase from the fungus Acremonium alcalophilum in vitro and in the gastrointestinal tract of broiler...
This study evaluates peptidoglycan hydrolysis by a microbial muramidase from the fungus Acremonium alcalophilum in vitro and in the gastrointestinal tract of broiler chickens. Peptidoglycan used for in vitro studies was derived from 5 gram-positive chicken gut isolate type strains. In vitro peptidoglycan hydrolysis was studied by three approaches: (a) helium ion microscopy to identify visual phenotypes of hydrolysis, (b) reducing end assay to quantify solubilization of peptidoglycan fragments, and (c) mass spectroscopy to estimate relative abundances of soluble substrates and reaction products. Visual effects of peptidoglycan hydrolysis could be observed by helium ion microscopy and the increase in abundance of soluble peptidoglycan due to hydrolysis was quantified by a reducing end assay. Mass spectroscopy confirmed the release of hydrolysis products and identified muropeptides from the five different peptidoglycan sources. Peptidoglycan hydrolysis in chicken crop, jejunum, and caecum samples was measured by quantifying the total and soluble muramic acid content. A significant increase in the proportion of the soluble muramic acid was observed in all three segments upon inclusion of the microbial muramidase in the diet.
Topics: Acremonium; Animals; Chickens; Gastrointestinal Tract; Hydrolysis; Male; Muramidase; Peptidoglycan
PubMed: 33693885
DOI: 10.1093/jimb/kuab008 -
Microbiology (Reading, England) Apr 2022Despite renewed interest, development of chemical biology methods to study peptidoglycan metabolism has lagged in comparison to the glycobiology field in general. To...
Despite renewed interest, development of chemical biology methods to study peptidoglycan metabolism has lagged in comparison to the glycobiology field in general. To address this, a panel of diamides were screened against the Gram-positive bacterium to identify inhibitors of bacterial growth. The screen identified the diamide masarimycin as a bacteriostatic inhibitor of growth with an MIC of 8 µM. The diamide inhibited detergent-induced autolysis in a concentration-dependent manner, indicating perturbation of peptidoglycan degradation as the mode-of-action. Cell based screening of masarimycin against a panel of autolysin mutants, identified a higher MIC against a Δ strain lacking an endo-N-acetylglucosaminidase involved in cell division. Subsequent biochemical and phenotypic analyses suggested that the higher MIC was due to an indirect interaction with LytB. Further analysis of changes to the cell surface in masarimycin treated cells identified the overexpression of several moonlighting proteins, including elongation factor Tu which is implicated in regulating cell shape. Checkerboard assays using masarimycin in concert with additional antibiotics identified an antagonistic relationship with the cell wall targeting antibiotic fosfomycin, which further supports a cell wall mode-of-action.
Topics: Anti-Bacterial Agents; Cell Wall; Diamide; N-Acetylmuramoyl-L-alanine Amidase; Peptidoglycan; Streptococcus pneumoniae
PubMed: 35467499
DOI: 10.1099/mic.0.001182