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Antimicrobial Agents and Chemotherapy Jun 2024
PubMed: 38864614
DOI: 10.1128/aac.00727-24 -
PLoS Pathogens Jun 2024Invertebrates lack the immune machinery underlying vertebrate-like acquired immunity. However, in many insects past infection by the same pathogen can 'prime' the immune...
Invertebrates lack the immune machinery underlying vertebrate-like acquired immunity. However, in many insects past infection by the same pathogen can 'prime' the immune response, resulting in improved survival upon reinfection. Here, we investigated the mechanistic basis and epidemiological consequences of innate immune priming in the fruit fly Drosophila melanogaster when infected with the gram-negative bacterial pathogen Providencia rettgeri. We find that priming in response to P. rettgeri infection is a long-lasting and sexually dimorphic response. We further explore the epidemiological consequences of immune priming and find it has the potential to curtail pathogen transmission by reducing pathogen shedding and spread. The enhanced survival of individuals previously exposed to a non-lethal bacterial inoculum coincided with a transient decrease in bacterial loads, and we provide strong evidence that the effect of priming requires the IMD-responsive antimicrobial-peptide Diptericin-B in the fat body. Further, we show that while Diptericin B is the main effector of bacterial clearance, it is not sufficient for immune priming, which requires regulation of IMD by peptidoglycan recognition proteins. This work underscores the plasticity and complexity of invertebrate responses to infection, providing novel experimental evidence for the effects of innate immune priming on population-level epidemiological outcomes.
Topics: Animals; Immunity, Innate; Drosophila melanogaster; Providencia; Drosophila Proteins; Female; Male; Enterobacteriaceae Infections; Antimicrobial Peptides
PubMed: 38857285
DOI: 10.1371/journal.ppat.1012308 -
ELife Jun 2024is a microbiota species in humans that can modulate host immunity (Griffin and Hang, 2022), but has also acquired antibiotic resistance and is a major cause of...
is a microbiota species in humans that can modulate host immunity (Griffin and Hang, 2022), but has also acquired antibiotic resistance and is a major cause of hospital-associated infections (Van Tyne and Gilmore, 2014). Notably, diverse strains of produce SagA, a highly conserved peptidoglycan hydrolase that is sufficient to promote intestinal immunity (Rangan et al., 2016; Pedicord et al., 2016; Kim et al., 2019) and immune checkpoint inhibitor antitumor activity (Griffin et al., 2021). However, the functions of SagA in were unknown. Here, we report that deletion of impaired growth and resulted in bulged and clustered enterococci due to defective peptidoglycan cleavage and cell separation. Moreover, Δ showed increased antibiotic sensitivity, yielded lower levels of active muropeptides, displayed reduced activation of the peptidoglycan pattern-recognition receptor NOD2, and failed to promote cancer immunotherapy. Importantly, the plasmid-based expression of SagA, but not its catalytically inactive mutant, restored Δ growth, production of active muropeptides, and NOD2 activation. SagA is, therefore, essential for growth, stress resistance, and activation of host immunity.
Topics: Enterococcus faecium; N-Acetylmuramoyl-L-alanine Amidase; Immune Checkpoint Inhibitors; Humans; Animals; Bacterial Proteins; Peptidoglycan; Mice
PubMed: 38857064
DOI: 10.7554/eLife.95297 -
FEBS Letters Jun 2024The FtsEX membrane complex constitutes an essential component of the ABC transporter superfamily, widely distributed among bacterial species. It governs peptidoglycan... (Review)
Review
The FtsEX membrane complex constitutes an essential component of the ABC transporter superfamily, widely distributed among bacterial species. It governs peptidoglycan degradation for cell division, acting as a signal transmitter rather than a substrate transporter. Through the ATPase activity of FtsE, it facilitates signal transmission from the cytosol across the membrane to the periplasm, activating associated peptidoglycan hydrolases. This review concentrates on the latest structural advancements elucidating the architecture of the FtsEX complex and its interplay with lytic enzymes or regulatory counterparts. The revealed three-dimensional structures unveil a landscape wherein a precise array of intermolecular interactions, preserved across diverse bacterial species, afford meticulous spatial and temporal control over the cell division process.
PubMed: 38849310
DOI: 10.1002/1873-3468.14953 -
Journal of Biotechnology Aug 2024Lysozyme, an antimicrobial agent, is extensively employed in the food and healthcare sectors to facilitate the breakdown of peptidoglycan. However, the methods to...
Lysozyme, an antimicrobial agent, is extensively employed in the food and healthcare sectors to facilitate the breakdown of peptidoglycan. However, the methods to improve its catalytic activity and secretory expression still need to be studied. In the present study, twelve lysozymes from different origins were heterologously expressed using the Komagataella phaffii expression system. Among them, the lysozyme from the European flat oyster Ostrea edulis (oeLYZ) showed the highest activity. Via a semi-rational approach to reduce the structural free energy, the double mutant Y15A/S39R (oeLYZ) with the catalytic activity 1.8-fold greater than that of the wild type was generated. Subsequently, different N-terminal fusion tags were employed to enhance oeLYZ expression. The fusion with peptide tag 6×Glu resulted in a remarkable increase in the recombinant oeLYZdm expression, from 2.81 × 10 U mL to 2.11 × 10 U mL in shake flask culture, and eventually reaching 2.05 × 10 U mL in a 3-L fermenter. The work produced the greatest amount of heterologous oeLYZ expression in microbial systems that are known to exist. Reducing the structural free energy and employing the N-terminal fusion tags are effective strategies to improve the catalytic activity and secretory expression of lysozyme.
Topics: Muramidase; Animals; Ostrea; Recombinant Proteins
PubMed: 38848819
DOI: 10.1016/j.jbiotec.2024.05.011 -
Applied and Environmental Microbiology Jun 2024Lytic enzymes, or lysins for short, break down peptidoglycan and interrupt the continuity of the cell wall, which, in turn, causes osmotic lysis of the bacterium. Their... (Review)
Review
Lytic enzymes, or lysins for short, break down peptidoglycan and interrupt the continuity of the cell wall, which, in turn, causes osmotic lysis of the bacterium. Their ability to destroy bacteria from without makes them promising antimicrobial agents that can be used as alternatives or supplements to antibiotics. In this paper, we briefly summarize basic terms and concepts used to describe lysin sequences and delineate major lysin groups. More importantly, we describe the domain repertoire found in lysins and critically review bioinformatic tools or databases which are used in studies of these enzymes (with particular emphasis on the repositories of Hidden Markov models). Finally, we present a novel comprehensive, meticulously curated set of lysin-related family and domain models, sort them into clusters that reflect major families, and demonstrate that the selected models can be used to efficiently search for new lysins.
PubMed: 38842338
DOI: 10.1128/aem.02361-23 -
Frontiers in Microbiology 2024Bacterium-like particles (BLP) are the peptidoglycan skeleton particles of lactic acid bacteria, which have high safety, mucosal delivery efficiency, and adjuvant...
Bacterium-like particles (BLP) are the peptidoglycan skeleton particles of lactic acid bacteria, which have high safety, mucosal delivery efficiency, and adjuvant effect. It has been widely used in recent years in the development of vaccines. Existing anchoring proteins for BLP surfaces are few in number, so screening and characterization of new anchoring proteins are necessary. In this research, we created the OACD (C-terminal domain of outer membrane protein A) to serve as an anchoring protein on the surface of BLP produced by the immunomodulatory bacteria 23017. We used red fluorescent protein (RFP) to demonstrate the novel surface display system's effectiveness, stability, and ability to be adapted to a wide range of lactic acid bacteria. Furthermore, this study employed this surface display method to develop a novel vaccine (called COB17) by using the multi-epitope antigen of as the model antigen. The vaccine can induce more than 50% protection rate against type A challenge in mice immunized with a single dose and has been tested through three routes. The vaccine yields protection rates of 75% for subcutaneous, 50% for intranasal, and 75% for oral immunization. Additionally, it elicits a strong mucosal immune response, markedly increasing levels of specific IgG, high-affinity IgG, specific IgA, and SIgA antibodies. Additionally, we used protein anchors (PA) and OACD simultaneous to show several antigens on the BLP surface. The discovery of novel BLP anchoring proteins may expand the possibilities for creating mucosal immunity subunit vaccines. Additionally, it may work in concert with PA to provide concepts for the creation of multivalent or multiple vaccines that may be used in clinical practice to treat complex illnesses.
PubMed: 38841059
DOI: 10.3389/fmicb.2024.1395837 -
The FEBS Journal Jun 2024Peptidoglycan DL-endopeptidases locally cleave the peptide stem of peptidoglycan in the bacterial cell wall. This process facilitates bacterial growth and division by...
Peptidoglycan DL-endopeptidases locally cleave the peptide stem of peptidoglycan in the bacterial cell wall. This process facilitates bacterial growth and division by loosening the rigid peptidoglycan layer. IseA binds to the active site of multiple DL-endopeptidases and inhibits excessive peptidoglycan degradation that leads to cell lysis. To better understand how IseA inhibits DL-endopeptidase activity, we determined the crystal structure of the peptidoglycan DL-endopeptidase CwlO/IseA complex and compared it with that of the peptidoglycan DL-endopeptidase LytE/IseA complex. Structural analyses showed significant differences between the hydrophobic pocket-binding residues of the DL-endopeptidases (F361 of CwlO and W237 of LytE). Additionally, binding assays showed that the F361 mutation of CwlO to the bulkier hydrophobic residue, tryptophan, increased its binding affinity for IseA, whereas mutation to alanine reduced the affinity. These analyses revealed that the hydrophobic pocket-binding residue of DL-endopeptidases determines IseA-binding affinity and is required for substrate-mimetic inhibition by IseA.
PubMed: 38840475
DOI: 10.1111/febs.17197 -
Microbiological Research Aug 2024As a major human and animal pathogen, Staphylococcus aureus can attach to medical implants (abiotic surface) or host tissues (biotic surface), and further establish... (Review)
Review
As a major human and animal pathogen, Staphylococcus aureus can attach to medical implants (abiotic surface) or host tissues (biotic surface), and further establish robust biofilms which enhances resistance and persistence to host immune system and antibiotics. Cell-wall-anchored proteins (CWAPs) covalently link to peptidoglycan, and largely facilitate the colonization of S. aureus on various surfaces (including adhesion and biofilm formation) and invasion into host cells (including adhesion, immune evasion, iron acquisition and biofilm formation). During biofilm formation, CWAPs function in adhesion, aggregation, collagen-like fiber network formation, and consortia formation. In this review, we firstly focus on the structural features of CWAPs, including their intracellular function and interactions with host cells, as well as the functions and ligand binding of CWAPs in different stages of S. aureus biofilm formation. Then, the roles of CWAPs in different biofilm processes with regards in development of therapeutic approaches are clarified, followed by the association between CWAPs genes and clonal lineages. By touching upon these aspects, we hope to provide comprehensive knowledge and clearer understanding on the CWAPs of S. aureus and their roles in biofilm formation, which may further aid in prevention and treatment infection and vaccine development.
Topics: Biofilms; Staphylococcus aureus; Humans; Staphylococcal Infections; Bacterial Proteins; Cell Wall; Bacterial Adhesion; Animals; Peptidoglycan
PubMed: 38833832
DOI: 10.1016/j.micres.2024.127782 -
MBio Jun 2024expresses a type IV protein secretion system (T4SS) that promotes contact-dependent killing of other bacteria and does so partly by secreting the effector TfcB. Here,...
expresses a type IV protein secretion system (T4SS) that promotes contact-dependent killing of other bacteria and does so partly by secreting the effector TfcB. Here, we report the structure of TfcB, comprising an N-terminal domain similar to the catalytic domain of glycosyl hydrolase (GH-19) chitinases and a C-terminal domain for recognition and translocation by the T4SS. Utilizing a two-hybrid assay to measure effector interactions with the T4SS coupling protein VirD4, we documented the existence of five more T4SS substrates. One of these was protein 20845, an annotated nuclease. A mutant lacking the gene for 20845 was impaired for killing , , and . Moreover, the cloned 20845 gene conferred robust toxicity, with the recombinant being rescued when 20845 was co-expressed with its cognate immunity protein. The 20845 effector was an 899 amino-acid protein, comprised of a GHH-nuclease domain in its N-terminus, a large central region of indeterminant function, and a C-terminus for secretion. Engineered variants of the 20845 gene that had mutations in the predicted catalytic site did not impede , indicating that the antibacterial effect of 20845 involves its nuclease activity. Using flow cytometry with DNA staining, we determined that 20845, but not its mutant variants, confers a loss in DNA content of target bacteria. Database searches revealed that uncharacterized homologs of 20845 occur within a range of bacteria. These data indicate that the T4SS promotes interbacterial competition through the action of multiple toxic effectors, including a potent, novel DNase.IMPORTANCE is a multi-drug-resistant, Gram-negative bacterium that is an emerging pathogen of humans. Patients with cystic fibrosis are particularly susceptible to infection. In hospital water systems and various types of infections, co-exists with other bacteria, including other pathogens such as . We previously demonstrated that has a functional VirB/D4 type VI protein secretion system (T4SS) that promotes contact-dependent killing of other bacteria. Since most work on antibacterial systems involves the type VI secretion system, this observation remains noteworthy. Moreover, currently stands alone as a model for a human pathogen expressing an antibacterial T4SS. Using biochemical, genetic, and cell biological approaches, we now report both the discovery of a novel antibacterial nuclease (TfdA) and the first structural determination of a bactericidal T4SS effector (TfcB).
PubMed: 38832773
DOI: 10.1128/mbio.01198-24