Single-molecule study on histone-like nucleoid-structuring protein (H-NS) paralogue in Pseudomonas aeruginosa: MvaU bears DNA organization mode similarities to MvaT.

Pseudomonas aeruginosa contains two distinct members of H-NS family of nucleoid-structuring proteins: MvaT and MvaU. Together, these proteins bind to the same regions of the chromosome and function coordinately in the regulation of hundreds of genes. Due to their structural similarity, they can associate to form heteromeric complexes.

Basis for the essentiality of H-NS family members in Pseudomonas aeruginosa.

Members of the histone-like nucleoid-structuring (H-NS) family of proteins have been shown to play important roles in silencing gene expression and in nucleoid compaction. In Pseudomonas aeruginosa, the two H-NS family members MvaT and MvaU are thought to bind the same AT-rich regions of the chromosome and function coordinately to control a common set of genes. Here we present evidence that the loss of both MvaT and MvaU cannot be tolerated because it results in the production of Pf4 phage that superinfect and kill cells or inhibit their growth.

Higher order oligomerization is required for H-NS family member MvaT to form gene-silencing nucleoprotein filament.

MvaT from Pseudomonas aeruginosa is a member of the histone-like nucleoid structuring protein (H-NS) family of nucleoid-associated proteins widely spread among Gram-negative bacteria that functions to repress the expression of many genes. Recently, it was reported that H-NS from Escherichia coli can form rigid nucleoproteins filaments on DNA, which are important for their gene-silencing function. This raises a question whether the gene-silencing function of MvaT, which has only ∼18% sequence similarity to H-NS, is also based on the formation of nucleoprotein filaments.

High-order oligomerization is required for the function of the H-NS family member MvaT in Pseudomonas aeruginosa.

H-NS is an abundant DNA-binding protein that has been implicated in the silencing of foreign DNA in several different bacteria. The ability of H-NS dimers to form higher-order oligomers is thought to aid the polymerization of the protein across AT-rich stretches of DNA and facilitate gene silencing. Although the oligomerization of H-NS from enteric bacteria has been the subject of intense investigation, little is known regarding the oligomerization of H-NS family members from bacteria outside of the enterobacteriaceae, many of which share little sequence similarity with their enteric counterparts.

The GacS/GacA signal transduction system of Pseudomonas aeruginosa acts exclusively through its control over the transcription of the RsmY and RsmZ regulatory small RNAs.

We report here the results of an analysis of the regulatory range of the GacS/GacA two-component system in Pseudomonas aeruginosa. Using microarrays, we identified a large number of genes that are regulated by the system, and detected a near complete overlap of these genes with those regulated by two small RNAs (sRNAs), RsmY and RsmZ, suggesting that the expression of all GacA-regulated genes is RsmY/Z-dependent. Using genome-wide DNA-protein interaction analyses, we identified only two genomic regions that associated specifically with GacA, located upstream of the rsmY and rsmZ genes.

H-NS family members function coordinately in an opportunistic pathogen.

The histone-like nucleoid structuring protein, H-NS, is a prominent global regulator of gene expression. Many Gram-negative bacteria contain multiple members of the H-NS family of proteins. Thus, a key question is whether H-NS family members have overlapping or distinct functions.

PecS is a global regulator of the symptomatic phase in the phytopathogenic bacterium Erwinia chrysanthemi 3937.

Pathogenicity of the enterobacterium Erwinia chrysanthemi (Dickeya dadantii), the causative agent of soft-rot disease in many plants, is a complex process involving several factors whose production is subject to temporal regulation during infection. PecS is a transcriptional regulator that controls production of various virulence factors. Here, we used microarray analysis to define the PecS regulon and demonstrated that PecS notably regulates a wide range of genes that could be linked to pathogenicity and to a group of genes concerned with evading host defenses.

The crystal structure of pectate lyase peli from soft rot pathogen Erwinia chrysanthemi in complex with its substrate.

The crystallographic structure of the family 3 polysaccharide lyase (PL-3) PelI from Erwinia chrysanthemi has been solved to 1.45 A resolution. It consists of an N-terminal domain harboring a fibronectin type III fold linked to a catalytic domain displaying a parallel beta-helix topology.

Direct evidence for the modulation of the activity of the Erwinia chrysanthemi quorum-sensing regulator ExpR by acylhomoserine lactone pheromone.

In Erwinia chrysanthemi production of pectic enzymes is controlled by a complex network involving several regulators. Among them is ExpR, the quorum-sensing regulatory protein. ExpR is a member of the LuxR family of transcriptional regulators, the activity of which is modulated by the binding of diffusible N-acylhomoserine lactone pheromones to the N-terminal receptor site of the proteins.

Synthesis and biological evaluation of homoserine lactone derived ureas as antagonists of bacterial quorum sensing.

A series of 15 racemic alkyl- and aryl-N-substituted ureas, derived from homoserine lactone, were synthesized and tested for their ability to competitively inhibit the action of 3-oxohexanoyl-l-homoserine lactone, the natural inducer of bioluminescence in the bacterium Vibrio fischeri. N-alkyl ureas with an alkyl chain of at least 4 carbon atoms, as well as certain ureas bearing a phenyl group at the extremity of the alkyl chain, were found to be significant antagonists. In the case of N-butyl urea, it has been shown that the antagonist activity was related to the inhibition of the dimerisation of the N-terminal domain of ExpR, a protein of the receptor LuxR family.

N-Sulfonyl homoserine lactones as antagonists of bacterial quorum sensing.

A series of 11 new analogues of N-acylhomoserine lactones in which the carboxamide bond was replaced by a sulfonamide one, has been synthesised. These compounds were evaluated for their ability to competitively inhibit the action of 3-oxohexanoyl-L-homoserine lactone, the natural ligand of the quorum sensing transcriptional regulator LuxR, which in turn activates expression of bioluminescence in the model bacterium Vibrio fischeri. Several compounds were found to display antagonist activity.

Crystallization of the pectate lyase PelI from Erwinia chrysanthemi and SAD phasing of a gold derivative.

The pectate lyase PelI is involved in the degradation of plant tissues by the phytopathogenic bacterium Erwinia chrysanthemi. It has been crystallized from a solution containing PEG 550 in the space group P2(1), with unit-cell parameters a = 61.6, b = 70.