A role for the Gram-negative outer membrane in bacterial shape determination.

The cell envelope of Gram-negative bacteria consists of three distinct layers: the cytoplasmic membrane, a cell wall made of peptidoglycan (PG), and an asymmetric outer membrane (OM) composed of phospholipid in the inner leaflet and lipopolysaccharide (LPS) glycolipid in the outer leaflet. The PG layer has long been thought to be the major structural component of the envelope protecting cells from osmotic lysis and providing them with their characteristic shape. In recent years, the OM has also been shown to be a load-bearing layer of the cell surface that fortifies cells against internal turgor pressure.

A role for the Gram-negative outer membrane in bacterial shape determination.

Unlabelled: The cell envelope of Gram-negative bacteria consists of three distinct layers: the cytoplasmic membrane, a cell wall made of peptidoglycan (PG), and an asymmetric outer membrane (OM) composed of phospholipid in the inner leaflet and lipopolysaccharide (LPS) glycolipid in the outer leaflet. The PG layer has long been thought to be the major structural component of the envelope protecting cells from osmotic lysis and providing them with their characteristic shape. In recent years, the OM has also been shown to be a load-bearing layer of the cell surface that fortifies cells against internal turgor pressure.

Growth and Division of the Peptidoglycan Matrix.

Most bacteria are surrounded by a peptidoglycan cell wall that defines their shape and protects them from osmotic lysis. The expansion and division of this structure therefore plays an integral role in bacterial growth and division. Additionally, the biogenesis of the peptidoglycan layer is the target of many of our most effective antibiotics.

Identification of potential regulatory domains within the MreC and MreD components of the cell elongation machinery.

The bacterial peptidoglycan (PG) cell wall maintains cell shape and prevents osmotic lysis. During growth of rod-shaped cells, PG is incorporated along the cell cylinder by the RodA-PBP2 synthase of the multi-protein Rod system (elongasome). Filaments of the actin-like MreB protein orient synthesis of the new PG material.

MltG activity antagonizes cell wall synthesis by both types of peptidoglycan polymerases in Escherichia coli.

Bacterial cells are surrounded by a peptidoglycan (PG) cell wall. This structure is essential for cell integrity and its biogenesis pathway is a key antibiotic target. Most bacteria utilize two types of synthases that polymerize glycan strands and crosslink them: class A penicillin-binding proteins (aPBPs) and complexes of SEDS proteins and class B PBPs (bPBPs).

Structural coordination of polymerization and crosslinking by a SEDS-bPBP peptidoglycan synthase complex.

The shape, elongation, division and sporulation (SEDS) proteins are a highly conserved family of transmembrane glycosyltransferases that work in concert with class B penicillin-binding proteins (bPBPs) to build the bacterial peptidoglycan cell wall. How these proteins coordinate polymerization of new glycan strands with their crosslinking to the existing peptidoglycan meshwork is unclear. Here, we report the crystal structure of the prototypical SEDS protein RodA from Thermus thermophilus in complex with its cognate bPBP at 3.

A central role for PBP2 in the activation of peptidoglycan polymerization by the bacterial cell elongation machinery.

Cell elongation in rod-shaped bacteria is mediated by the Rod system, a conserved morphogenic complex that spatially controls cell wall assembly by the glycan polymerase RodA and crosslinking enzyme PBP2. Using Escherichia coli as a model system, we identified a PBP2 variant that promotes Rod system function when essential accessory components of the machinery are inactivated. This PBP2 variant hyperactivates cell wall synthesis in vivo and stimulates the activity of RodA-PBP2 complexes in vitro.

Structure of the peptidoglycan polymerase RodA resolved by evolutionary coupling analysis.

The shape, elongation, division and sporulation (SEDS) proteins are a large family of ubiquitous and essential transmembrane enzymes with critical roles in bacterial cell wall biology. The exact function of SEDS proteins was for a long time poorly understood, but recent work has revealed that the prototypical SEDS family member RodA is a peptidoglycan polymerase-a role previously attributed exclusively to members of the penicillin-binding protein family. This discovery has made RodA and other SEDS proteins promising targets for the development of next-generation antibiotics.

Bacterial cell wall biogenesis is mediated by SEDS and PBP polymerase families functioning semi-autonomously.

Multi-protein complexes organized by cytoskeletal proteins are essential for cell wall biogenesis in most bacteria. Current models of the wall assembly mechanism assume that class A penicillin-binding proteins (aPBPs), the targets of penicillin-like drugs, function as the primary cell wall polymerases within these machineries. Here, we use an in vivo cell wall polymerase assay in Escherichia coli combined with measurements of the localization dynamics of synthesis proteins to investigate this hypothesis.

Extension of the Caenorhabditis elegans Pharyngeal M1 neuron axon is regulated by multiple mechanisms.

The guidance of axons to their correct targets is a critical step in development. The C. elegans pharynx presents an attractive system to study neuronal pathfinding in the context of a developing organ.

Neuronal expression of fibroblast growth factor receptors in zebrafish.

Fibroblast growth factor (FGF) signaling is important for a host of developmental processes such as proliferation, differentiation, tissue patterning, and morphogenesis. In vertebrates, FGFs signal through a family of four fibroblast growth factor receptors (FGFR 1-4), one of which is duplicated in zebrafish (FGFR1). Here we report the mRNA expression of the five known zebrafish fibroblast growth factor receptors at five developmental time points (24, 36, 48, 60, and 72h postfertilization), focusing on expression within the central nervous system.

The olsA gene mediates the synthesis of an ornithine lipid in Pseudomonas aeruginosa during growth under phosphate-limiting conditions, but is not involved in antimicrobial peptide susceptibility.

Pseudomonas aeruginosa responds to phosphate limitation by inducing the expression of phosphate transport systems, phosphatases, hemolysins and a DNase, many of which are important for virulence. Here we report that under phosphate-limiting conditions, P. aeruginosa produces a phosphate-free ornithine lipid (OL) as the primary membrane lipid.