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Streptococcal S protein activates a peptidoglycan cell wall repair and modification complex to promote resistance of Streptococcus pneumoniae to lysozyme and LL-37, and increase virulence during infection.

The peptidoglycan sacculus maintains bacterial cell shape and provides mechanical strength to resist osmotic challenge. In this Review, Vollmer and colleagues describe recent insights into the mechanisms of peptidoglycan synthesis in Gram-negative bacteria and how this process is regulated by cytoskeletal and outer-membrane components.

Peptidoglycan stem peptides in the Gram-negative bacterial cell wall regulate the insertion of essential outer membrane proteins, thus representing a potential target for antibiotic design.

Streptococcus pneumoniae develop a state of genetic competence, in which the bacteria can acquire exogenous DNA; the competent bacteria also secrete enzymes that trigger the lysis of neighboring non-competent cells. Now the structure of pneumococcal autolysin LytC provides insight into its role in cell wall metabolism and fratricide.

Curved cell shapes are common among bacteria, but the underlying morphogenetic mechanisms are incompletely understood. Here, the authors identify an outer-membrane protein complex that promotes cell curvature in Rhodospirillum rubrum by forming helical ribbon structures that modulate the dynamics of cell wall biosynthesis, biasing cell growth towards the cell’s outer curve.

Proteins with a catalytically inactive LytM-type endopeptidase domain regulate cell wall-degrading enzymes in bacteria. Here, Izquierdo-Martinez et al. show that one such protein, DipM, coordinates different peptidoglycan-remodeling pathways to ensure proper cell constriction and daughter cell separation in the model bacterium Caulobacter crescentus.

Cells of the predatory bacterium Bdellovibrio bacteriovorus, which invades and replicates within the periplasm of other bacteria, have a characteristic curved rod shape. Here, Banks et al. show that a peptidoglycan hydrolase is required for the curved shape, and this facilitates invasion of prey cells.

Bacterial cell wall enzymes and their precursors are critical targets for antibiotic development. Here, the authors investigate several biosynthetic enzymes with their substrates and show that the passage of substrates and products in the pathway is controlled by their relative binding affinities.

The distinction between different cell-envelope architectures has defined much of our thinking about bacterial systematics, but the evolution of different envelope layers has been harder to understand. A recent publication focused on the non-model organism Acetonema longum provides important clues to the possible origin of the second membrane typical of Gram-negative bacteria.

The amidotransferase MurT/GatD complex catalyzes peptidoglycan precursor amidation in some Gram-positive bacteria. Here the authors present the crystal structure of the Streptococcus pneumoniae MurT/GatD complex and provide mechanistic insights, which are of interest for drug development.

Proteins FtsZ, ZipA, and either PBP1A or PBP1B are required for the synthesis of preseptal peptidoglycan at the future cell division site in E. coli. Here, Pazos et al. provide evidence that ZipA and FtsA-FtsN connect the cytosolic FtsZ ring with the membrane-anchored PBPs.

Penicillin inhibits growth of chlamydial pathogens despite their lack of a conventional peptidoglycan cell wall. Here the authors report that the chlamydial amidase, AmiA, which can rescue cell division defects of an E. coli amiAmutant, has dual activity as a penicillin sensitive, lipid II-targetting carboxypeptidase.

Chlamydiae are sensitive to beta-lactam antibiotics, which target cell-wall peptidoglycan (PG), but it is unclear whether these bacteria possess PG. Pilhofer et al. now demonstrate that cell walls of a chlamydial species, Protochlamydia amoebophila, contain a PG layer.

The cell wall of Gram-positive bacteria consists of peptidoglycan modified with other polymers, such as the capsular polysaccharide. Here, the authors reconstitute the biosynthesis of capsular polysaccharide and elucidate its interplay with the cell wall biosynthetic machinery.

Teichoic acid is bound to peptidoglycan (wall teichoic acid, WTA) or to membrane glycolipids (lipoteichoic acid, LTA) in most Gram-positive bacteria. Here, the authors identify a putative ligase required for the assembly of LTA, but not WTA, and important for Streptococcus pneumoniae virulence in mouse models.

The bacterium Bdellovibrio bacteriovorus invades and kills other bacteria, but it is unclear how it avoids degradation of its own cell wall. Here the authors identify the B. bacteriovorusprotein Bd3460 as an endopeptidase inhibitor that prevents hydrolysis of the predator’s peptidoglycan during invasion of prey.

EzrA regulates the polymerization of FtsZ, a tubulin-like protein and main component of the Z-ring, which drives cell division in bacteria. Here the authors describe the crystal structure of EzrA and demonstrate that it shares structural and functional properties with eukaryotic spectrins.

In this Review Egan, Errington and Vollmer discuss new insights into the molecular mechanisms of peptidoglycan synthesis, sacculus growth regulation and bacterial morphology, as well as how bacteria achieve robust cell wall growth under different conditions and stresses.

The secretion of Salmonella Typhi typhoid toxin requires translocation across the peptidoglycan layer through the action of a ld-transpeptidase. Subsequent outer membrane perturbation fully releases toxin for host cell intoxication.

Fluorescent d-amino acid incorporation reveals host–prey cell wall modification during Bdellovibrio bacteriovorus predation including pore formation and l,d-transpeptidase-mediated prey strengthening.

Documented cases of horizontal gene transfer from bacteria to eukaryotes are rare, but now, not only is a new class of transferred genes identified, the function of one representative is also demonstrated in its new setting, where it controls bacterial growth.

The use of an in vitro system in which key proteins involved in cell division are attached to supported lipid bilayers reveals that membrane-bound cytosolic peptides of FtsN and FtsQ co-migrate with treadmilling FtsZ–FtsA filaments via a diffusion-and-capture mechanism, elucidating how FtsZ dynamics regulate the distribution of peptidoglycan synthases.