NMR study of the interaction between MinC and FtsZ and modeling of the FtsZ:MinC complex.

The Min system is a key spatial regulator of cell division in rod-shaped bacteria and the first FtsZ negative modulator to be recognized. Nevertheless, despite extensive genetic and in vitro studies, the molecular mechanism used by MinC to inhibit Z-ring formation remains incompletely understood. The crystallization of FtsZ in complex with other negative regulators such as SulA and MciZ has provided important structural information to corroborate in vitro experiments and establish the mechanism of Z-ring antagonism by these modulators.

The Division Defect of a Double Mutant Can Be Suppressed by Spx-Dependent and Spx-Independent Mechanisms.

During growth, bacteria increase in size and divide. Division is initiated by the formation of the Z-ring, a ring-like cytoskeletal structure formed by treadmilling protofilaments of the tubulin homolog FtsZ. FtsZ localization is thought to be controlled by the Min and Noc systems, and here we explore why cell division fails at high temperature when the Min and Noc systems are simultaneously mutated.

Noc Corrals Migration of FtsZ Protofilaments during Cytokinesis in Bacillus subtilis.

Bacteria that divide by binary fission form FtsZ rings at the geometric midpoint of the cell between the bulk of the replicated nucleoids. In , the DNA- and membrane-binding Noc protein is thought to participate in nucleoid occlusion by preventing FtsZ rings from forming over the chromosome. To explore the role of Noc, we used time-lapse fluorescence microscopy to monitor FtsZ and the nucleoid of cells growing in microfluidic channels.

Merulinic acid C overcomes gentamicin resistance in Enterococcus faecium.

Enterococci are gram-positive, widespread nosocomial pathogens that in recent years have developed resistance to various commonly employed antibiotics. Since finding new infection-control agents based on secondary metabolites from organisms has proved successful for decades, natural products are potentially useful sources of compounds with activity against enterococci. Herein are reported the results of a natural product library screening based on a whole-cell assay against a gram-positive model organism, which led to the isolation of a series of anacardic acids identified by analysis of their spectroscopic data and by chemical derivatizations.

The phosphatidic acid pathway enzyme PlsX plays both catalytic and channeling roles in bacterial phospholipid synthesis.

PlsX is the first enzyme in the pathway that produces phosphatidic acid in Gram-positive bacteria. It makes acylphosphate from acyl-acyl carrier protein (acyl-ACP) and is also involved in coordinating phospholipid and fatty acid biosyntheses. PlsX is a peripheral membrane enzyme in but how it associates with the membrane remains largely unknown.

Membrane fluidity adjusts the insertion of the transacylase PlsX to regulate phospholipid biosynthesis in Gram-positive bacteria.

PlsX plays a central role in the coordination of fatty acid and phospholipid biosynthesis in Gram-positive bacteria. PlsX is a peripheral membrane acyltransferase that catalyzes the conversion of acyl-ACP to acyl-phosphate, which is in turn utilized by the polytopic membrane acyltransferase PlsY on the pathway of bacterial phospholipid biosynthesis. We have recently studied the interaction between PlsX and membrane phospholipids and , and observed that membrane association is necessary for the efficient transfer of acyl-phosphate to PlsY.

Violacein Targets the Cytoplasmic Membrane of Bacteria.

Violacein is a tryptophan-derived purple pigment produced by environmental bacteria, which displays multiple biological activities, including strong inhibition of Gram-positive pathogens. Here, we applied a combination of experimental approaches to identify the mechanism by which violacein kills Gram-positive bacteria. Fluorescence microscopy showed that violacein quickly and dramatically permeabilizes B.

Association of magnetotactic multicellular prokaryotes with Pseudoalteromonas species in a natural lagoon environment.

Magnetotactic bacteria, for the most part, are free-living, motile, unicellular prokaryotes that inhabit almost all marine and freshwater environments. One notable exception to the unicellular mode, however, are the magnetotactic multicellular prokaryotes. These morphologically unique prokaryotes (e.

Synthesis, biophysical and functional studies of two BP100 analogues modified by a hydrophobic chain and a cyclic peptide.

Antimicrobial peptides (AMPs) work as a primary defense against pathogenic microorganisms. BP100, (KKLFKKILKYL-NH), a rationally designed short, highly cationic AMP, acts against many bacteria, displaying low toxicity to eukaryotic cells. Previously we found that its mechanism of action depends on membrane surface charge and on peptide-to-lipid ratio.

The stringent response plays a key role in Bacillus subtilis survival of fatty acid starvation.

The stringent response is a universal adaptive mechanism to protect bacteria from nutritional and environmental stresses. The role of the stringent response during lipid starvation has been studied only in Gram-negative bacteria. Here, we report that the stringent response also plays a crucial role in the adaptation of the model Gram-positive Bacillus subtilis to fatty acid starvation.

Revisiting the cell biology of the acyl-ACP:phosphate transacylase PlsX suggests that the phospholipid synthesis and cell division machineries are not coupled in Bacillus subtilis.

PlsX is a central enzyme of phospholipid synthesis in bacteria, converting acyl-ACP to acyl-phosphate on the pathway to phosphatidic acid formation. PlsX has received attention because it plays a key role in the coordination of fatty acid and phospholipid synthesis. Recently, PlsX was also suggested to coordinate membrane synthesis with cell division in Bacillus subtilis.

Backbone and side chain NMR assignments of Geobacillus stearothermophilus ZapA allow identification of residues that mediate the interaction of ZapA with FtsZ.

Bacterial division begins with the formation of a contractile protein ring at midcell, which constricts the bacterial envelope to generate two daughter cells. The central component of the division ring is FtsZ, a tubulin-like protein capable of self-assembling into filaments which further associate into a higher order structure known as the Z ring. Proteins that bind to FtsZ play a crucial role in the formation and regulation of the Z ring.

FtsZ filament capping by MciZ, a developmental regulator of bacterial division.

Cytoskeletal structures are dynamically remodeled with the aid of regulatory proteins. FtsZ (filamentation temperature-sensitive Z) is the bacterial homolog of tubulin that polymerizes into rings localized to cell-division sites, and the constriction of these rings drives cytokinesis. Here we investigate the mechanism by which the Bacillus subtilis cell-division inhibitor, MciZ (mother cell inhibitor of FtsZ), blocks assembly of FtsZ.

Backbone and side chain NMR assignments for the N-terminal domain of the cell division regulator MinC from Bacillus subtilis.

Bacterial cell division proteins must assemble at the middle of the cell to ensure the viability of both daughter cells. The first step in the assembly of the cell division apparatus is the polymerization of the tubulin-like protein FtsZ into a ring-shaped scaffold, the Z-ring. The Min system contributes to the spatial precision of division by inhibiting FtsZ polymerization at the cell poles.

Genetic and biochemical characterization of the MinC-FtsZ interaction in Bacillus subtilis.

Cell division in bacteria is regulated by proteins that interact with FtsZ and modulate its ability to polymerize into the Z ring structure. The best studied of these regulators is MinC, an inhibitor of FtsZ polymerization that plays a crucial role in the spatial control of Z ring formation. Recent work established that E.

RefZ facilitates the switch from medial to polar division during spore formation in Bacillus subtilis.

During sporulation, Bacillus subtilis redeploys the division protein FtsZ from midcell to the cell poles, ultimately generating an asymmetric septum. Here, we describe a sporulation-induced protein, RefZ, that facilitates the switch from a medial to a polar FtsZ ring placement. The artificial expression of RefZ during vegetative growth converts FtsZ rings into FtsZ spirals, arcs, and foci, leading to filamentation and lysis.

DivIVA-mediated polar localization of ComN, a posttranscriptional regulator of Bacillus subtilis.

ComN (YrzD) is a small, 98-amino-acid protein recently shown to be involved in the posttranscriptional control of the late competence comE operon in Bacillus subtilis. We show here that ComN localizes to the division site and cell poles in a DivIVA-dependent fashion. Yeast two-hybrid and glutathione S-transferase pulldown experiments showed that ComN interacts directly with DivIVA.

Vectorial signalling mechanism required for cell-cell communication during sporulation in Bacillus subtilis.

Spore formation in Bacillus subtilis takes place in a sporangium consisting of two chambers, the forespore and the mother cell, which are linked by pathways of cell-cell communication. One pathway, which couples the proteolytic activation of the mother cell transcription factor σ(E) to the action of a forespore synthesized signal molecule, SpoIIR, has remained enigmatic. Signalling by SpoIIR requires the protein to be exported to the intermembrane space between forespore and mother cell, where it will interact with and activate the integral membrane protease SpoIIGA.

Structure and mode of action of microplusin, a copper II-chelating antimicrobial peptide from the cattle tick Rhipicephalus (Boophilus) microplus.

Microplusin, a Rhipicephalus (Boophilus) microplus antimicrobial peptide (AMP) is the first fully characterized member of a new family of cysteine-rich AMPs with histidine-rich regions at the N and C termini. In the tick, microplusin belongs to the arsenal of innate defense molecules active against bacteria and fungi. Here we describe the NMR solution structure of microplusin and demonstrate that the protein binds copper II and iron II.

Cytological characterization of YpsB, a novel component of the Bacillus subtilis divisome.

Cell division in bacteria is carried out by an elaborate molecular machine composed of more than a dozen proteins and known as the divisome. Here we describe the characterization of a new divisome protein in Bacillus subtilis called YpsB. Sequence comparisons and phylogentic analysis demonstrated that YpsB is a paralog of the division site selection protein DivIVA.

AMIN domains have a predicted role in localization of diverse periplasmic protein complexes.

We describe AMIN (Amidase N-terminal domain), a novel protein domain found specifically in bacterial periplasmic proteins. AMIN domains are widely distributed among peptidoglycan hydrolases and transporter protein families. Based on experimental data, contextual information and phyletic profiles, we suggest that AMIN domains mediate the targeting of periplasmic or extracellular proteins to specific regions of the bacterial envelope.

GroES/GroEL and DnaK/DnaJ have distinct roles in stress responses and during cell cycle progression in Caulobacter crescentus.

Misfolding and aggregation of protein molecules are major threats to all living organisms. Therefore, cells have evolved quality control systems for proteins consisting of molecular chaperones and proteases, which prevent protein aggregation by either refolding or degrading misfolded proteins. DnaK/DnaJ and GroES/GroEL are the best-characterized molecular chaperone systems in bacteria.

Premature targeting of a cell division protein to midcell allows dissection of divisome assembly in Escherichia coli.

Cell division in Escherichia coli requires the recruitment of at least 10 essential proteins to the bacterial midcell. Recruitment of these proteins follows a largely linear dependency pathway in which depletion of one cell division protein leads to the absence from the division site of "downstream" proteins in the pathway. Analysis of events that underlie this pathway is complicated by the fact that a protein's ability to recruit "downstream" proteins is dependent on its own recruitment by "upstream" proteins.

Assembly dynamics of FtsZ rings in Bacillus subtilis and Escherichia coli and effects of FtsZ-regulating proteins.

FtsZ is the major cytoskeletal component of the bacterial cell division machinery. It forms a ring-shaped structure (the Z ring) that constricts as the bacterium divides. Previous in vivo experiments with green fluorescent protein-labeled FtsZ and fluorescence recovery after photobleaching have shown that the Escherichia coli Z ring is extremely dynamic, continually remodeling itself with a half time of 30 s, similar to microtubules in the mitotic spindle.