Discovery of (Dihydro)pyrazine N-Oxides via Genome Mining in Pseudomonas.

Overexpression of the Pseudomonas virulence factor ( pvf) biosynthetic operon led to the identification of a family of pyrazine N-oxides (PNOs), including a novel dihydropyrazine N,N'-dioxide (dPNO) metabolite. The nonribosomal peptide synthetase responsible for production of (d)PNOs was characterized, and a biosynthetic pathway for (d)PNOs was proposed. This work highlights the unique chemistry catalyzed by pvf-encoded enzymes and sets the stage for bioactivity studies of the metabolites produced by the virulence pathway.

Domestication of Lambda Phage Genes into a Putative Third Type of Replicative Helicase Matchmaker.

At the onset of the initiation of chromosome replication, bacterial replicative helicases are recruited and loaded on the DnaA-oriC nucleoprotein platform, assisted by proteins like DnaC/DnaI or DciA. Two orders of bacteria appear, however, to lack either of these factors, raising the question of the essentiality of these factors in bacteria. Through a phylogenomic approach, we identified a pair of genes that could have substituted for dciA.

DciA is an ancestral replicative helicase operator essential for bacterial replication initiation.

Delivery of the replicative helicase onto DNA is an essential step in the initiation of replication. In bacteria, DnaC (in Escherichia coli) and DnaI (in Bacillus subtilis) are representative of the two known mechanisms that assist the replicative helicase at this stage. Here, we establish that these two strategies cannot be regarded as prototypical of the bacterial domain since dnaC and dnaI (dna[CI]) are present in only a few bacterial phyla.

Regional Control of Chromosome Segregation in Pseudomonas aeruginosa.

Chromosome segregation in bacteria occurs concomitantly with DNA replication, and the duplicated regions containing the replication origin oriC are generally the first to separate and migrate to their final specific location inside the cell. In numerous bacterial species, a three-component partition machinery called the ParABS system is crucial for chromosome segregation. This is the case in the gammaproteobacterium Pseudomonas aeruginosa, where impairing the ParABS system is very detrimental for growth, as it increases the generation time and leads to the formation of anucleate cells and to oriC mispositioning inside the cell.

σ Factor and Anti-σ Factor That Control Swarming Motility and Biofilm Formation in Pseudomonas aeruginosa.

Unlabelled: Pseudomonas aeruginosa is capable of causing a variety of acute and chronic infections. Here, we provide evidence that sbrR (PA2895), a gene previously identified as required during chronic P. aeruginosa respiratory infection, encodes an anti-σ factor that inhibits the activity of its cognate extracytoplasmic-function σ factor, SbrI (PA2896).

Anr and its activation by PlcH activity in Pseudomonas aeruginosa host colonization and virulence.

Pseudomonas aeruginosa hemolytic phospholipase C (PlcH) degrades phosphatidylcholine (PC), an abundant lipid in cell membranes and lung surfactant. A ΔplcHR mutant, known to be defective in virulence in animal models, was less able to colonize epithelial cell monolayers and was defective in biofilm formation on plastic when grown in lung surfactant. Microarray analyses found that strains defective in PlcH production had lower levels of Anr-regulated transcripts than the wild type.

Chromosomal organization and segregation in Pseudomonas aeruginosa.

The study of chromosomal organization and segregation in a handful of bacteria has revealed surprising variety in the mechanisms mediating such fundamental processes. In this study, we further emphasized this diversity by revealing an original organization of the Pseudomonas aeruginosa chromosome. We analyzed the localization of 20 chromosomal markers and several components of the replication machinery in this important opportunistic γ-proteobacteria pathogen.

Long-range chromosome organization in E. coli: a site-specific system isolates the Ter macrodomain.

The organization of the Escherichia coli chromosome into a ring composed of four macrodomains and two less-structured regions influences the segregation of sister chromatids and the mobility of chromosomal DNA. The structuring of the terminus region (Ter) into a macrodomain relies on the interaction of the protein MatP with a 13-bp target called matS repeated 23 times in the 800-kb-long domain. Here, by using a new method that allows the transposition of any chromosomal segment at a defined position on the genetic map, we reveal a site-specific system that restricts to the Ter region a constraining process that reduces DNA mobility and delays loci segregation.

Monalysin, a novel ß-pore-forming toxin from the Drosophila pathogen Pseudomonas entomophila, contributes to host intestinal damage and lethality.

Pseudomonas entomophila is an entomopathogenic bacterium that infects and kills Drosophila. P. entomophila pathogenicity is linked to its ability to cause irreversible damages to the Drosophila gut, preventing epithelium renewal and repair.

A secondary metabolite acting as a signalling molecule controls Pseudomonas entomophila virulence.

Pseudomonas entomophila is an entomopathogenic bacterium that is lethal to Drosophila melanogaster within 1-2 days of ingestion of high doses. Flies orally infected with P. entomophila rapidly succumb despite the induction of both local and systemic immune responses.

Epigenetic control of virulence gene expression in Pseudomonas aeruginosa by a LysR-type transcription regulator.

Phenotypic variation within an isogenic bacterial population is thought to ensure the survival of a subset of cells in adverse conditions. The opportunistic pathogen Pseudomonas aeruginosa variably expresses several phenotypes, including antibiotic resistance, biofilm formation, and the production of CupA fimbriae. Here we describe a previously unidentified bistable switch in P.

Association of hemolytic activity of Pseudomonas entomophila, a versatile soil bacterium, with cyclic lipopeptide production.

Pseudomonas entomophila is an entomopathogenic bacterium that is able to infect and kill Drosophila melanogaster upon ingestion. Its genome sequence suggests that it is a versatile soil bacterium closely related to Pseudomonas putida. The GacS/GacA two-component system plays a key role in P.

Bacterial strategies to overcome insect defences.

Recent genetic and molecular analyses have revealed how several strategies enable bacteria to persist and overcome insect immune defences. Genetic and genomic tools that can be used with Drosophila melanogaster have enabled the characterization of the pathways that are used by insects to detect bacterial invaders and combat infection. Conservation of bacterial virulence factors and insect immune repertoires indicates that there are common strategies of host invasion and pathogen eradication.

Crystal structure and RNA binding of the Tex protein from Pseudomonas aeruginosa.

Tex is a highly conserved bacterial protein that likely functions in a variety of transcriptional processes. Here, we describe two crystal structures of the 86-kDa Tex protein from Pseudomonas aeruginosa at 2.3 and 2.

Local and global regulators linking anaerobiosis to cupA fimbrial gene expression in Pseudomonas aeruginosa.

The cupA gene cluster of Pseudomonas aeruginosa encodes components and assembly factors of a putative fimbrial structure that enable this opportunistic pathogen to form biofilms on abiotic surfaces. In P. aeruginosa the control of cupA gene expression is complex, with the H-NS-like MvaT protein functioning to repress phase-variable (on/off) expression of the operon.

Multiple sensors control reciprocal expression of Pseudomonas aeruginosa regulatory RNA and virulence genes.

The opportunistic pathogen Pseudomonas aeruginosa is responsible for a wide range of acute and chronic infections. The transition to chronic infections is accompanied by physiological changes in the bacteria favoring formation of biofilm communities. Here we report the identification of LadS, a hybrid sensor kinase that controls the reciprocal expression of genes for type III secretion and biofilm-promoting polysaccharides.

Repression of phase-variable cup gene expression by H-NS-like proteins in Pseudomonas aeruginosa.

The cupA gene cluster of Pseudomonas aeruginosa encodes components of a putative fimbrial structure that enable this opportunistic human pathogen to form biofilms on abiotic surfaces. In P. aeruginosa, cupA gene expression is repressed by MvaT, a putative transcription regulator thought to belong to the H-NS family of nucleoid-associated proteins that typically function by repressing transcription.

ExsE, a secreted regulator of type III secretion genes in Pseudomonas aeruginosa.

Type III secretion systems are toxin delivery systems that are present in a large number of pathogens. A hallmark of all type III secretion systems studied to date is that expression of one or more of their components is induced upon cell contact. It has been proposed that this induction is controlled by a negative regulator that is itself secreted by means of the type III secretion machinery.

The pel genes of the Pseudomonas aeruginosa PAK strain are involved at early and late stages of biofilm formation.

Pseudomonas aeruginosa is a Gram-negative bacterium associated with nosocomial infections and cystic fibrosis. Chronic bacterial infections are increasingly associated with the biofilm lifestyle in which microcolonies are embedded in an extracellular matrix. Screening procedures for identifying biofilm-deficient strains have allowed the characterization of several key determinants involved in this process.