Aquatic environment drives the emergence of cell wall-deficient dormant forms in Listeria.

Stressed bacteria can enter a dormant viable but non-culturable (VBNC) state. VBNC pathogens pose an increased health risk as they are undetectable by growth-based techniques and can wake up back into a virulent state. Although widespread in bacteria, the mechanisms governing this phenotypic switch remain elusive.

Molecular mechanisms underlying the structural diversity of rhamnose-rich cell wall polysaccharides in lactococci.

In Gram-positive bacteria, cell wall polysaccharides (CWPS) play critical roles in bacterial cell wall homeostasis and bacterial interactions with their immediate surroundings. In lactococci, CWPS consist of two components: a conserved rhamnan embedded in the peptidoglycan layer and a surface-exposed polysaccharide pellicle (PSP), which are linked together to form a large rhamnose-rich CWPS (Rha-CWPS). PSP, whose structure varies from strain to strain, is a receptor for many bacteriophages infecting lactococci.

MreE (PBP2) variants facilitate clinical disease during cephalosporin exposures.

Cephalosporins are the most common triggers of healthcare-associated infections (CDI). Here, we confirm gene-level drivers of cephalosporin resistance and their roles in promoting disease. Genomic-epidemiologic analyses of 306 isolates from a hospital surveillance program monitoring asymptomatic carriers and CDI patients identified prevalent third-generation cephalosporin resistance to ceftriaxone at >256 ug/mL in 26% of isolates.

Reduced synthesis of phospho-polysaccharide in Lactococcus as a strategy to evade phage infection.

Lactococcus spp. are applied routinely in dairy fermentations and their consistent growth and associated acidification activity is critical to ensure the quality and safety of fermented dairy foods. Bacteriophages pose a significant threat to such fermentations and thus it is imperative to study how these bacteria may evade their viral predators in the relevant confined settings.

Structural studies of the deacylated glycolipids and lipoteichoic acid of Lactococcus cremoris 3107.

Lactococcus cremoris and Lactococcus lactis are among the most extensively exploited species of lactic acid bacteria in dairy fermentations. The cell wall of lactococci, like other Gram-positive bacteria, possesses a thick peptidoglycan layer, which may incorporate cell wall polysaccharides (CWPS), wall teichoic acids (WTA), and/or lipoteichoic acids (LTA). In this study, we report the isolation, purification and structural analysis of the carbohydrate moieties of glycolipids (GL) and LTA of the L.

PBP2b Mutations Improve the Growth of Phage-Resistant Lacking Polysaccharide Pellicle.

Lactococcus lactis and Lactococcus cremoris are Gram-positive lactic acid bacteria widely used as starter in milk fermentations. Lactococcal cells are covered with a polysaccharide pellicle (PSP) that was previously shown to act as the receptor for numerous bacteriophages of the class. Thus, mutant strains lacking PSP are phage resistant.

Structure-function analysis of DltE reveals D-alanylated lipoteichoic acids as direct cues supporting juvenile growth.

Metazoans establish mutually beneficial interactions with their resident microorganisms. However, our understanding of the microbial cues contributing to host physiology remains elusive. Previously, we identified a bacterial machinery encoded by the operon involved in 's juvenile growth promotion by .

Microbe-mediated intestinal NOD2 stimulation improves linear growth of undernourished infant mice.

The intestinal microbiota is known to influence postnatal growth. We previously found that a strain of (strain Lp) buffers the adverse effects of chronic undernutrition on the growth of juvenile germ-free mice. Here, we report that Lp sustains the postnatal growth of malnourished conventional animals and supports both insulin-like growth factor-1 (IGF-1) and insulin production and activity.

Host genetic requirements for DNA release of lactococcal phage TP901-1.

The first step in phage infection is the recognition of, and adsorption to, a receptor located on the host cell surface. This reversible host adsorption step is commonly followed by an irreversible event, which involves phage DNA delivery or release into the bacterial cytoplasm. The molecular components that trigger this latter event are unknown for most phages of Gram-positive bacteria.

Structural variations and roles of rhamnose-rich cell wall polysaccharides in Gram-positive bacteria.

Rhamnose-rich cell wall polysaccharides (Rha-CWPSs) have emerged as crucial cell wall components of numerous Gram-positive, ovoid-shaped bacteria-including streptococci, enterococci, and lactococci-of which many are of clinical or biotechnological importance. Rha-CWPS are composed of a conserved polyrhamnose backbone with side-chain substituents of variable size and structure. Because these substituents contain phosphate groups, Rha-CWPS can also be classified as polyanionic glycopolymers, similar to wall teichoic acids, of which they appear to be functional homologs.

DltC acts as an interaction hub for AcpS, DltA and DltB in the teichoic acid D-alanylation pathway of Lactiplantibacillus plantarum.

Teichoic acids (TA) are crucial for the homeostasis of the bacterial cell wall as well as their developmental behavior and interplay with the environment. TA can be decorated by different modifications, modulating thus their biochemical properties. One major modification consists in the esterification of TA by D-alanine, a process known as D-alanylation.

The Phagocytosis of and Its Immunomodulatory Properties on Human Monocyte-Derived Dendritic Cells Depend on the Expression of Lc-p75, a Bacterial Peptidoglycan Hydrolase.

The human gut symbiont (previously ) is under intense research due to its wide range of immunomodulatory effects on the human host. Dendritic cells (DCs) are crucial players in the direct and indirect communication with lactobacilli in the gastrointestinal tract. Here, we demonstrate that human monocyte-derived DCs (moDCs) are able to engulf BL23, in which the intact bacterial cell wall and morphology have a key role.

AsnB Mediates Amidation of -Diaminopimelic Acid Residues in the Peptidoglycan of and Affects Bacterial Surface Properties and Host Cell Invasion.

A mutant of ScottA with a transposon in the 5' untranslated region of the gene was identified to be hypersensitive to the antimicrobial -cinnamaldehyde. Here, we report the functional characterization of AsnB in peptidoglycan (PG) modification and intracellular infection. While AsnB of is annotated as a glutamine-dependent asparagine synthase, sequence alignment showed that this protein is closely related to a subset of homologs that catalyze the amidation of -diaminopimelic acid (DAP) residues in the peptidoglycan of other bacterial species.

Ser/Thr Kinase-Dependent Phosphorylation of the Peptidoglycan Hydrolase CwlA Controls Its Export and Modulates Cell Division in Clostridioides difficile.

Cell growth and division require a balance between synthesis and hydrolysis of the peptidoglycan (PG). Inhibition of PG synthesis or uncontrolled PG hydrolysis can be lethal for the cells, making it imperative to control peptidoglycan hydrolase (PGH) activity. The synthesis or activity of several key enzymes along the PG biosynthetic pathway is controlled by the Hanks-type serine/threonine kinases (STKs).

Cyclic di-AMP Oversight of Counter-Ion Osmolyte Pools Impacts Intrinsic Cefuroxime Resistance in Lactococcus lactis.

The broadly conserved cyclic di-AMP (c-di-AMP) is a conditionally essential bacterial second messenger. The pool of c-di-AMP is fine-tuned through diadenylate cyclase and phosphodiesterase activities, and direct binding of c-di-AMP to proteins and riboswitches allows the regulation of a broad spectrum of cellular processes. c-di-AMP has a significant impact on intrinsic β-lactam antibiotic resistance in Gram-positive bacteria; however, the reason for this is currently unclear.

Pili and other surface proteins influence the structure and the nanomechanical properties of Lactococcus lactis biofilms.

Lactic acid bacteria, in particular Lactococcus lactis, are widely used in the food industry, for the control and/or the protection of the manufacturing processes of fermented food. While L. lactis has been reported to form compact and uniform biofilms it was recently shown that certain strains able to display pili at their surface form more complex biofilms exhibiting heterogeneous and aerial structures.

The CWPS Rubik's cube: Linking diversity of cell wall polysaccharide structures with the encoded biosynthetic machinery of selected Lactococcus lactis strains.

The biosynthetic machinery for cell wall polysaccharide (CWPS) production in lactococci is encoded by a large gene cluster, designated cwps. This locus displays considerable variation among lactococcal genomes, previously prompting a classification into three distinct genotypes (A-C). In the present study, the cwps loci of 107 lactococcal strains were compared, revealing the presence of a fourth cwps genotype (type D).

Cell wall homeostasis in lactic acid bacteria: threats and defences.

Lactic acid bacteria (LAB) encompasses industrially relevant bacteria involved in food fermentations as well as health-promoting members of our autochthonous microbiota. In the last years, we have witnessed major progresses in the knowledge of the biology of their cell wall, the outermost macrostructure of a Gram-positive cell, which is crucial for survival. Sophisticated biochemical analyses combined with mutation strategies have been applied to unravel biosynthetic routes that sustain the inter- and intra-species cell wall diversity within LAB.

Complete Structure of the Enterococcal Polysaccharide Antigen (EPA) of Vancomycin-Resistant Enterococcus faecalis V583 Reveals that EPA Decorations Are Teichoic Acids Covalently Linked to a Rhamnopolysaccharide Backbone.

All enterococci produce a complex polysaccharide called the nterococcal olysaccharide ntigen (EPA). This polymer is required for normal cell growth and division and for resistance to cephalosporins and plays a critical role in host-pathogen interaction. The EPA contributes to host colonization and is essential for virulence, conferring resistance to phagocytosis during the infection.

Analysis of Homotypic Interactions of Pili Using Single-Cell Force Spectroscopy.

Cell surface proteins of Gram-positive bacteria play crucial roles in their adhesion to abiotic and biotic surfaces. Pili are long and flexible proteinaceous filaments known to enhance bacterial initial adhesion. They promote surface colonization and are thus considered as essential factors in biofilm cohesion.

Three distinct glycosylation pathways are involved in the decoration of cell wall glycopolymers.

Extracytoplasmic sugar decoration of glycopolymer components of the bacterial cell wall contributes to their structural diversity. Typically, the molecular mechanism that underpins such a decoration process involves a three-component glycosylation system (TGS) represented by an undecaprenyl-phosphate (Und-P) sugar-activating glycosyltransferase (Und-P GT), a flippase, and a polytopic glycosyltransferase (PolM GT) dedicated to attaching sugar residues to a specific glycopolymer. Here, using bioinformatic analyses, CRISPR-assisted recombineering, structural analysis of cell wall-associated polysaccharides (CWPS) through MALDI-TOF MS and methylation analysis, we report on three such systems in the bacterium On the basis of sequence similarities, we first identified three gene pairs, , , and , each encoding an Und-P GT and a PolM GT, as potential TGS component candidates.

A dual-chain assembly pathway generates the high structural diversity of cell-wall polysaccharides in .

In , cell-wall polysaccharides (CWPSs) act as receptors for many bacteriophages, and their structural diversity among strains explains, at least partially, the narrow host range of these viral predators. Previous studies have reported that lactococcal CWPS consists of two distinct components, a variable chain exposed at the bacterial surface, named polysaccharide pellicle (PSP), and a more conserved rhamnan chain anchored to, and embedded inside, peptidoglycan. These two chains appear to be covalently linked to form a large heteropolysaccharide.

The Ser/Thr Kinase PrkC Participates in Cell Wall Homeostasis and Antimicrobial Resistance in Clostridium difficile.

is the leading cause of antibiotic-associated diarrhea in adults. During infection, must detect the host environment and induce an appropriate survival strategy. Signal transduction networks involving serine/threonine kinases (STKs) play key roles in adaptation, as they regulate numerous physiological processes.

Distinct and Specific Role of NlpC/P60 Endopeptidases LytA and LytB in Cell Elongation and Division of .

Peptidoglycan (PG) is an essential lattice of the bacterial cell wall that needs to be continuously remodeled to allow growth. This task is ensured by the concerted action of PG synthases that insert new material in the pre-existing structure and PG hydrolases (PGHs) that cleave the PG meshwork at critical sites for its processing. Contrasting with that contains more than 35 PGHs, is a non-sporulating rod-shaped bacterium that is predicted to possess a minimal set of 12 PGHs.