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.

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 .

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.

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.

Another Brick in the Wall: a Rhamnan Polysaccharide Trapped inside Peptidoglycan of .

Polysaccharides are ubiquitous components of the Gram-positive bacterial cell wall. In , a polysaccharide pellicle (PSP) forms a layer at the cell surface. The PSP structure varies among lactococcal strains; in MG1363, the PSP is composed of repeating hexasaccharide phosphate units.