The peptidoglycan and biofilm matrix of Staphylococcus epidermidis undergo structural changes when exposed to human platelets.

Staphylococcus epidermidis is a bacterium frequently isolated from contaminated platelet concentrates (PCs), a blood product used to treat bleeding disorders in transfusion patients. PCs offer an accidental niche for colonization of S. epidermidis by forming biofilms and thus avoiding clearance by immune factors present in this milieu.

Bacterial secretion of D-arginine controls environmental microbial biodiversity.

Bacteria face tough competition in polymicrobial communities. To persist in a specific niche, many species produce toxic extracellular effectors to interfere with the growth of nearby microbes. These effectors include the recently reported non-canonical D-amino acids (NCDAAs).

Determinants of Bacterial Morphology: From Fundamentals to Possibilities for Antimicrobial Targeting.

Bacterial morphology is extremely diverse. Specific shapes are the consequence of adaptive pressures optimizing bacterial fitness. Shape affects critical biological functions, including nutrient acquisition, motility, dispersion, stress resistance and interactions with other organisms.

Chemometric Analysis of Bacterial Peptidoglycan Reveals Atypical Modifications That Empower the Cell Wall against Predatory Enzymes and Fly Innate Immunity.

Peptidoglycan is a fundamental structure for most bacteria. It contributes to the cell morphology and provides cell wall integrity against environmental insults. While several studies have reported a significant degree of variability in the chemical composition and organization of peptidoglycan in the domain Bacteria, the real diversity of this polymer is far from fully explored.

Ultra-Sensitive, High-Resolution Liquid Chromatography Methods for the High-Throughput Quantitative Analysis of Bacterial Cell Wall Chemistry and Structure.

High-performance liquid chromatography (HPLC) analysis has been critical for determining the structural and chemical complexity of the cell wall. However this method is very time consuming in terms of sample preparation and chromatographic separation. Here we describe (1) optimized methods for peptidoglycan isolation from both Gram-negative and Gram-positive bacteria that dramatically reduce the sample preparation time, and (2) the application of the fast and highly efficient ultra-performance liquid chromatography (UPLC) technology to muropeptide separation and quantification.

High-throughput, Highly Sensitive Analyses of Bacterial Morphogenesis Using Ultra Performance Liquid Chromatography.

The bacterial cell wall is a network of glycan strands cross-linked by short peptides (peptidoglycan); it is responsible for the mechanical integrity of the cell and shape determination. Liquid chromatography can be used to measure the abundance of the muropeptide subunits composing the cell wall. Characteristics such as the degree of cross-linking and average glycan strand length are known to vary across species.

A novel peptidoglycan D,L-endopeptidase induced by Salmonella inside eukaryotic cells contributes to virulence.

Bacteria remodel peptidoglycan structure in response to environmental changes. Many enzymes are involved in peptidoglycan metabolism; however, little is known about their responsiveness in a defined environment or the modes they assist bacteria to adapt to new niches. Here, we focused in peptidoglycan enzymes that intracellular bacterial pathogens use inside eukaryotic cells.

Structural constraints and dynamics of bacterial cell wall architecture.

The peptidoglycan wall (PG) is a unique structure which confers physical strength and defined shape to bacteria. It consists of a net-like macromolecule of peptide interlinked glycan chains overlying the cell membrane. The structure and layout of the PG dictates that the wall has to be continuously modified as bacteria go through division, morphological differentiation, and adaptive responses.

Peptidoglycan remodeling by the coordinated action of multispecific enzymes.

The peptidoglycan (PG) cell wall constitutes the main defense barrier of bacteria against environmental insults and acts as communication interface. The biochemistry of this macromolecule has been well characterized throughout the years but recent discoveries have unveiled its chemical plasticity under environmental stresses. Non-canonical D-amino acids (NCDAA) are produced and released to the extracellular media by diverse bacteria.

Bile-induced peptidoglycan remodelling in Salmonella enterica.

Changes in the peptidoglycan (PG) structure of Salmonella enterica are detected in the presence of a sublethal concentration of sodium deoxycholate (DOC): (i) lower proportions of Braun lipoprotein (Lpp)-bound muropeptides; (ii) reduced levels of muropeptides cross-linked by L(meso)-diaminopimelyl-D(meso)-diaminopimelic acid (L-D) peptide bridges (3-3 cross-links). Similar structural changes are found in S. enterica cultures adapted to grow in the presence of a lethal concentration of DOC, suggesting that reduced anchoring of Braun protein to PG and low occurrence of 3-3 cross-links may increase S.

Peptidoglycan plasticity in bacteria: emerging variability of the murein sacculus and their associated biological functions.

The peptidoglycan (PG) sacculus once thought to be just a reinforcing, static and uniform structure, is fast becoming recognized as a dynamic cell constituent involved in every aspect of bacterial physiology. Recent advances showed that in addition to 'classical' tasks-as an essential element to define bacterial shape, size, division and resistance to osmotic stress-the sacculus plays very important roles in many other fields. The very few chemical and structural changes that were once considered as bizarre, or maybe exotic exceptions, are now universally accepted as fundamental pieces in bacterial cell wall adaptation to different kinds of environmental stresses; immune response; intra-specific and inter-specific signalling and antibiotics, just to mention a few.

Isolation and preparation of bacterial cell walls for compositional analysis by ultra performance liquid chromatography.

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the face of turgor pressures several atmospheres in magnitude. Across the diverse shapes and sizes of the bacterial kingdom, the cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by short peptides. Peptidoglycan's central importance to bacterial physiology underlies its use as an antibiotic target and has motivated genetic, structural, and cell biological studies of how it is robustly assembled during growth and division.

Structural basis for the broad specificity of a new family of amino-acid racemases.

Broad-spectrum amino-acid racemases (Bsrs) enable bacteria to generate noncanonical D-amino acids, the roles of which in microbial physiology, including the modulation of cell-wall structure and the dissolution of biofilms, are just beginning to be appreciated. Here, extensive crystallographic, mutational, biochemical and bioinformatic studies were used to define the molecular features of the racemase BsrV that enable this enzyme to accommodate more diverse substrates than the related PLP-dependent alanine racemases. Conserved residues were identified that distinguish BsrV and a newly defined family of broad-spectrum racemases from alanine racemases, and these residues were found to be key mediators of the multispecificity of BrsV.

Modes of cell wall growth differentiation in rod-shaped bacteria.

A bacterial cell takes on the challenge to preserve and reproduce its shape at every generation against a substantial internal pressure by surrounding itself with a mechanical support, a peptidoglycan cell wall. The enlargement of the cell wall via net incorporation of precursors into the pre-existing wall conditions bacterial growth and morphology. However, generation, reproduction and/or modification of a specific shape requires that the incorporation takes place at precise locations for a defined time period.

Eliminating a set of four penicillin binding proteins triggers the Rcs phosphorelay and Cpx stress responses in Escherichia coli.

Penicillin binding proteins (PBPs) are responsible for synthesizing and modifying the bacterial cell wall, and in Escherichia coli the loss of several nonessential low-molecular-weight PBPs gives rise to abnormalities in cell shape and division. To determine whether these proteins help connect the flagellar basal body to the peptidoglycan wall, we surveyed a set of PBP mutants and found that motility in an agar migration assay was compromised by the simultaneous absence of four enzymes: PBP4, PBP5, PBP7, and AmpH. A wild-type copy of any one of these restored migration, and complementation depended on the integrity of the PBP active-site serine.

Peptidoglycan at its peaks: how chromatographic analyses can reveal bacterial cell wall structure and assembly.

The peptidoglycan (PG) cell wall is a unique macromolecule responsible for both shape determination and cellular integrity under osmotic stress in virtually all bacteria. A quantitative understanding of the relationships between PG architecture, morphogenesis, immune system activation and pathogenesis can provide molecular-scale insights into the function of proteins involved in cell wall synthesis and cell growth. High-performance liquid chromatography (HPLC) has played an important role in our understanding of the structural and chemical complexity of the cell wall by providing an analytical method to quantify differences in chemical composition.

In Situ probing of newly synthesized peptidoglycan in live bacteria with fluorescent D-amino acids.

Tracking a bug's life: Peptidoglycan (PG) of diverse bacteria is labeled by exploiting the tolerance of cells for incorporating different non-natural D-amino acids. These nontoxic D-amino acids preferably label the sites of active PG synthesis, thereby enabling fine spatiotemporal tracking of cell-wall dynamics in phylogenetically and morphologically diverse bacteria. HCC = 7-hydroxycoumarin, NBD = 7-nitrobenzofurazan, TAMRA = carboxytetramethylrhodamine.

Complete genome sequence of Hirschia baltica type strain (IFAM 1418(T)).

The family Hyphomonadaceae within the Alphaproteobacteria is largely comprised of bacteria isolated from marine environments with striking morphologies and an unusual mode of cell growth. Here, we report the complete genome sequence Hirschia baltica, which is only the second a member of the Hyphomonadaceae with a published genome sequence. H.

Homogeneous incorporation of secondary cell wall polysaccharides to the cell wall of Thermus thermophilus HB27.

Regular surface protein layers (S-layers) from most Gram-positive bacteria and from the ancestral bacterium Thermus thermophilus attach to pyruvylated polysaccharides (SCWP) covalently bound to the peptidoglycan through their SLH domain. However, it is not known whether the synthesis of SCWP and S-layer is coordinated enough as to follow a similar pattern of incorporation to the cell wall during growth. In this work we analyse the localization of newly synthesized SCWP on the cell wall of T.

Peptidoglycan plasticity in bacteria: stress-induced peptidoglycan editing by noncanonical D-amino acids.

It has been generally assumed that the role of D-amino acids in bacterial physiology is rather limited. However, recent new evidence demonstrated that millimolar concentrations of noncanonical D-amino acids are synthesized and released to the environment by bacteria from diverse phyla. These D-amino acids help bacteria adapt to environmental challenges by modulating the structure and composition of the peptidoglycan (PG).

Escherichia coli low-molecular-weight penicillin-binding proteins help orient septal FtsZ, and their absence leads to asymmetric cell division and branching.

Escherichia coli cells lacking low-molecular-weight penicillin-binding proteins (LMW PBPs) exhibit morphological alterations that also appear when the septal protein FtsZ is mislocalized, suggesting that peptidoglycan modification and division may work together to produce cell shape. We found that in strains lacking PBP5 and other LMW PBPs, higher FtsZ concentrations increased the frequency of branched cells and incorrectly oriented Z rings by 10- to 15-fold. Invagination of these rings produced improperly oriented septa, which in turn gave rise to asymmetric cell poles that eventually elongated into branches.

Polar growth in the Alphaproteobacterial order Rhizobiales.

Elongation of many rod-shaped bacteria occurs by peptidoglycan synthesis at discrete foci along the sidewall of the cells. However, within the Rhizobiales, there are many budding bacteria, in which new cell growth is constrained to a specific region. The phylogeny of the Rhizobiales indicates that this mode of zonal growth may be ancestral.

Localized synthesis of the outer envelope from Thermus thermophilus.

In agreement with its distinct phylogenetic origin, the envelope of Thermus thermophilus consists of a complex pattern of layers with properties intermediate between those of Gram positives and Proteobacteria. Its cell wall of Gram positive composition is surrounded by an outer envelope that includes a crystalline layer scaffold built up by the SlpA protein, lipids and polysaccharides. The synthesis of this outer envelope has been studied by confocal microscopy.

AmpH, a bifunctional DD-endopeptidase and DD-carboxypeptidase of Escherichia coli.

In Escherichia coli, low-molecular-mass penicillin-binding proteins (LMM PBPs) are important for correct cell morphogenesis. These enzymes display DD-carboxypeptidase and/or dd-endopeptidase activities associated with maturation and remodeling of peptidoglycan (PG). AmpH has been classified as an AmpH-type class C LMM PBP, a group closely related to AmpC β-lactamases.

Deciphering morphological determinants of the helix-shaped Leptospira.

Leptospira spp. are thin, highly motile, slow-growing spirochetes that can be distinguished from other bacteria on the basis of their unique helical shape. Defining the mechanisms by which these bacteria generate and maintain this atypical morphology should greatly enhance our understanding of the fundamental physiology of these pathogens.