Strains Deficient in the Clp Chaperone-Protease Genes Have Reduced Virulence in a Murine Model of Pneumonia.

has emerged as a significant opportunistic Gram-negative pathogen and causative agent of nosocomial pneumonia especially in immunocompromised individuals in intensive care units. Recent advances to understand the contribution and function of virulence factors in its pathogenesis have begun to elucidate how this bacterium interacts with immune cells and its interesting mechanisms for multi-antibiotic resistance. Taking advantage of the availability of the AB5075 transposon mutant library, we investigated the impact of the Clp genes, which encode for a chaperone-protease responsible for the degradation of misfolded proteins, on bacterial virulence in a model of pneumonia using C57BL/6 mice and survival within J774.

Depletion of Alveolar Macrophages Increases Pulmonary Neutrophil Infiltration, Tissue Damage, and Sepsis in a Murine Model of Acinetobacter baumannii Pneumonia.

has emerged as an important etiological agent of hospital-related infections, especially nosocomial pneumonia. The virulence factors of this bacterium and their interactions with the cells and molecules of the immune system just recently began to be extensively studied. Here, we investigated the impact of alveolar macrophages on pneumonia using a mouse model of infection and a flexible tissue culture system.

The small molecule nitazoxanide selectively disrupts BAM-mediated folding of the outer membrane usher protein.

Bacterial pathogens assemble adhesive surface structures termed pili or fimbriae to initiate and sustain infection of host tissues. Uropathogenic , the primary causative agent of urinary tract infections, expresses type 1 and P pili required for colonization of the bladder and kidney, respectively. These pili are assembled by the conserved chaperone-usher (CU) pathway, in which a periplasmic chaperone works together with an outer membrane (OM) usher protein to build and secrete the pilus fiber.

SatS is a chaperone for the SecA2 protein export pathway.

The SecA2 protein export system is critical for the virulence of . However, the mechanism of this export pathway remains unclear. Through a screen for suppressors of a mutant, we identified a new player in the mycobacterial SecA2 pathway that we named SatS for ec2 (wo) uppressor.

The apolipoprotein N-acyl transferase Lnt is dispensable for growth in Acinetobacter species.

Directing the flow of protein traffic is a critical task faced by all cellular organisms. In Gram-negative bacteria, this traffic includes lipoproteins. Lipoproteins are synthesized as precursors in the cytoplasm and receive their acyl modifications upon export across the inner membrane.

Inhibitor of intramembrane protease RseP blocks the σ response causing lethal accumulation of unfolded outer membrane proteins.

The outer membrane (OM) of Gram-negative bacteria forms a robust permeability barrier that blocks entry of toxins and antibiotics. Most OM proteins (OMPs) assume a β-barrel fold, and some form aqueous channels for nutrient uptake and efflux of intracellular toxins. The Bam machine catalyzes rapid folding and assembly of OMPs.

Structural Similarities and Differences between Two Functionally Distinct SecA Proteins, Mycobacterium tuberculosis SecA1 and SecA2.

Unlabelled: While SecA is the ATPase component of the major bacterial secretory (Sec) system, mycobacteria and some Gram-positive pathogens have a second paralog, SecA2. In bacteria with two SecA paralogs, each SecA is functionally distinct, and they cannot compensate for one another. Compared to SecA1, SecA2 exports a distinct and smaller set of substrates, some of which have roles in virulence.

Suppressor analysis reveals a role for SecY in the SecA2-dependent protein export pathway of Mycobacteria.

All bacteria use the conserved Sec pathway to transport proteins across the cytoplasmic membrane, with the SecA ATPase playing a central role in the process. Mycobacteria are part of a small group of bacteria that have two SecA proteins: the canonical SecA (SecA1) and a second, specialized SecA (SecA2). The SecA2-dependent pathway exports a small subset of proteins and is required for Mycobacterium tuberculosis virulence.

Conformation-specific labeling of BamA and suppressor analysis suggest a cyclic mechanism for β-barrel assembly in Escherichia coli.

In gram-negative bacteria, integral outer membrane β-barrel proteins (OMPs) are assembled by the beta-barrel assembly machine (Bam) complex. The essential components of this complex are the OMP BamA [which contains a carboxyl-terminal β-barrel and an amino-terminal periplasmic module composed of five polypeptide transport associated (POTRA) domains] and the lipoprotein BamD. In Escherichia coli, the Bam complex also contains three nonessential lipoproteins (BamBCE), all of which require the barrel-proximal POTRA domain (P5) for stable interactions with BamA.

Making a beta-barrel: assembly of outer membrane proteins in Gram-negative bacteria.

The outer membrane (OM) of Gram-negative bacteria is an essential organelle that serves as a selective permeability barrier by keeping toxic compounds out of the cell while allowing vital nutrients in. How the OM and its constituent lipid and protein components are assembled remains an area of active research. In this review, we describe our current understanding of how outer membrane proteins (OMPs) are delivered to and then assembled in the OM of the model Gram-negative organism Escherichia coli.

BamE modulates the Escherichia coli beta-barrel assembly machine component BamA.

Biogenesis of the outer membrane (OM) is an essential process in gram-negative bacteria. One of the key steps of OM biogenesis is the assembly of integral outer membrane beta-barrel proteins (OMPs) by a protein machine called the Bam complex. In Escherichia coli, the Bam complex is composed of the essential proteins BamA and BamD and three nonessential lipoproteins, BamB, BamC, and BamE.

The Accessory SecA2 System of Mycobacteria Requires ATP Binding and the Canonical SecA1.

In bacteria, the majority of exported proteins are transported by the general Sec pathway from their site of synthesis in the cytoplasm across the cytoplasmic membrane. The essential SecA ATPase powers this Sec-mediated export. Mycobacteria possess two nonredundant SecA homologs: SecA1 and SecA2.

Identification of functional Tat signal sequences in Mycobacterium tuberculosis proteins.

The twin-arginine translocation (Tat) pathway is a system used by some bacteria to export proteins out from the cytosol to the cell surface or extracellular environment. A functional Tat pathway exists in the important human pathogen Mycobacterium tuberculosis. Identification of the substrates exported by the Tat pathway can help define the role that this pathway plays in the physiology and pathogenesis of M.

A new twist on an old pathway--accessory Sec [corrected] systems.

The export of proteins from their site of synthesis in the cytoplasm across the inner membrane is an important aspect of bacterial physiology. Because the location of extracytoplasmic proteins is ideal for host-pathogen interactions, protein export is also important to bacterial virulence. In bacteria, there are conserved protein export systems that are responsible for the majority of protein export: the general secretion (Sec) pathway and the twin-arginine translocation pathway.

ATPase activity of Mycobacterium tuberculosis SecA1 and SecA2 proteins and its importance for SecA2 function in macrophages.

The Sec-dependent translocation pathway that involves the essential SecA protein and the membrane-bound SecYEG translocon is used to export many proteins across the cytoplasmic membrane. Recently, several pathogenic bacteria, including Mycobacterium tuberculosis, were shown to possess two SecA homologs, SecA1 and SecA2. SecA1 is essential for general protein export.

ASK1, a SKP1 homolog, is required for nuclear reorganization, presynaptic homolog juxtaposition and the proper distribution of cohesin during meiosis in Arabidopsis.

Nuclear reorganization and juxtaposition of homologous chromosomes at late leptotene/early zygotene are essential steps before chromosome synapsis at pachytene. We report the results of detailed studies, which demonstrate that nuclear reorganization and homolog juxtapositioning processes are defective in a null mutant, ask1-1. Our results from 4, 6-diamino-2-phenylindole (DAPI)-stained spreads showed that the "synizetic knot", which is typically found in wild type (WT) meiosis during late leptotene and zygotene, was missing in the ask1-1 mutant.