Microcolony formation by the opportunistic pathogen Pseudomonas aeruginosa requires pyruvate and pyruvate fermentation.

A hallmark of the biofilm architecture is the presence of microcolonies. However, little is known about the underlying mechanisms governing microcolony formation. In the pathogen Pseudomonas aeruginosa, microcolony formation is dependent on the two-component regulator MifR, with mifR mutant biofilms exhibiting an overall thin structure lacking microcolonies, and overexpression of mifR resulting in hyper-microcolony formation.

Analysis of the Pseudomonas aeruginosa regulon controlled by the sensor kinase KinB and sigma factor RpoN.

Alginate overproduction by Pseudomonas aeruginosa, also known as mucoidy, is associated with chronic endobronchial infections in cystic fibrosis. Alginate biosynthesis is initiated by the extracytoplasmic function sigma factor (σ(22); AlgU/AlgT). In the wild-type (wt) nonmucoid strains, such as PAO1, AlgU is sequestered to the cytoplasmic membrane by the anti-sigma factor MucA that inhibits alginate production.

The novel Pseudomonas aeruginosa two-component regulator BfmR controls bacteriophage-mediated lysis and DNA release during biofilm development through PhdA.

Biofilms are surface-adhered bacterial communities encased in an extracellular matrix composed of polysaccharides, proteins, and extracellular (e)DNA, with eDNA required for biofilm formation and integrity. Here we demonstrate that eDNA release is controlled by BfmR, a regulator essential for Pseudomonas aeruginosa biofilm development. Expression of bfmR coincided with localized cell death and DNA release, and could be stimulated by conditions resulting in membrane perturbation and cell lysis.

Pseudomonas aeruginosa AlgR represses the Rhl quorum-sensing system in a biofilm-specific manner.

AlgR controls numerous virulence factors in Pseudomonas aeruginosa, including alginate, hydrogen cyanide production, and type IV pilus-mediated twitching motility. In this study, the role of AlgR in biofilms was examined in continuous-flow and static biofilm assays. Strain PSL317 (DeltaalgR) produced one-third the biofilm biomass of wild-type strain PAO1.

Interleukin-17 receptor deficiency results in impaired synovial expression of interleukin-1 and matrix metalloproteinases 3, 9, and 13 and prevents cartilage destruction during chronic reactivated streptococcal cell wall-induced arthritis.

Objective: To examine the role of interleukin-17 receptor (IL-17R) signaling in cartilage destruction and its interrelationship with synovial IL-1 expression during chronic reactivated streptococcal cell wall (SCW)-induced arthritis.

Methods: SCW arthritis was repeatedly induced in wild-type (WT) and IL-17R-deficient (IL-17R-/-) mice. At different time points, joint inflammation was assessed by using calipers to measure joint swelling.

Requirement of IL-17 receptor signaling in radiation-resistant cells in the joint for full progression of destructive synovitis.

IL-17 is a proinflammatory cytokine suspected to be involved in inflammatory and autoimmune diseases such as rheumatoid arthritis. In the present study, we report that IL-17R signaling is required in radiation-resistant cells in the joint for full progression of chronic synovitis and bone erosion. Repeated injections of Gram-positive bacterial cell wall fragments (streptococcal cell wall) directly into the knee joint of naive IL-17R-deficient (IL-17R-/-) mice had no effect on the acute phase of arthritis but prevented progression to chronic destructive synovitis as was noted in wild-type (wt) mice.

Altered phenotype of dextran sulfate sodium colitis in interferon regulatory factor-1 knock-out mice.

Background And Aims: Interferon regulatory factor-1 (IRF-1) is a transcription factor with antiviral, proinflammatory and tumor suppressor properties. We examined the role of IRF-1 in dextran sulfate sodium colitis, a murine model of inflammatory bowel disease, to determine if absence of the gene would protect against colitis.

Methods: C57BL/6J mice with a targeted disruption of IRF-1 and wild-type C57BL/6J controls received five 7-day cycles of 2% dextran sulfate sodium alternating with five 7-day cycles of water.

Central role of toll-like receptor 4 signaling and host defense in experimental pneumonia caused by Gram-negative bacteria.

Toll-like receptor 4 (TLR4) has been identified as a receptor for lipopolysaccharide. However, the precise role of TLR4 in regulating gene expression in response to an infection caused by gram-negative bacteria has not been fully elucidated. The role of TLR4 signaling in coordinating gene expression was assessed by gene expression profiling in lung tissue in a mouse model of experimental pneumonia with a low-dose infection of Klebsiella pneumoniae.

The transcriptional regulator AlgR controls cyanide production in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic lung infections in cystic fibrosis (CF) patients. One characteristic of P. aeruginosa CF isolates is the overproduction of the exopolysaccharide alginate, controlled by AlgR.

Transcriptome analysis of Pseudomonas aeruginosa after interaction with human airway epithelial cells.

The transcriptional profile of Pseudomonas aeruginosa after interactions with primary normal human airway epithelial cells was determined using Affymetrix GeneChip technology. Gene expression profiles indicated that various genes involved in phosphate acquisition and iron scavenging were differentially regulated.

Identification of AlgR-regulated genes in Pseudomonas aeruginosa by use of microarray analysis.

The Pseudomonas aeruginosa transcriptional regulator AlgR controls a variety of different processes, including alginate production, type IV pilus function, and virulence, indicating that AlgR plays a pivotal role in the regulation of gene expression. In order to characterize the AlgR regulon, Pseudomonas Affymetrix GeneChips were used to generate the transcriptional profiles of (i) P. aeruginosa PAO1 versus its algR mutant in mid-logarithmic phase, (ii) P.

Cutting edge: roles of Toll-like receptor 4 and IL-23 in IL-17 expression in response to Klebsiella pneumoniae infection.

Local production of IL-17 is a significant factor in effective host defense against Gram-negative bacteria. However, the proximal events mediating IL-17 elaboration by T cells remain unclear. In this study, we show in vivo that intact Toll-like receptor 4 signaling in the lung is required for induction of both the p19 transcript of IL-23 and IL-17 protein elaboration in response to Klebsiella pneumoniae.

Acute alcohol inhibits TNF-alpha processing in human monocytes by inhibiting TNF/TNF-alpha-converting enzyme interactions in the cell membrane.

Alcohol abuse has long been known to adversely affect innate immune responses and predispose to infections. One cellular mechanism responsible for this effect is alcohol-induced suppression of TNF-alpha by mononuclear phagocytes. We undertook experiments to better understand the cellular mechanisms by which alcohol dose-dependently suppresses TNF elaboration by human monocytes.

c-Myc is required for the glucose-mediated induction of metabolic enzyme genes.

Glucose exerts powerful effects on hepatocyte gene transcription by mechanisms that are incompletely understood. c-Myc regulates hepatic glucose metabolism by increasing glycolytic enzyme gene transcription while concomitantly decreasing gluconeogenic and ketogenic enzyme gene expression. However, the molecular mechanisms by which c-Myc exerts these effects is not known.