Biofilm dispersal in Xanthomonas campestris is controlled by cell–cell signaling role for the DSF/rpf regulatory system in biofilm formation and/or dispersal. Biofilm formation and dispersal in the black rot pathogen Xanthomonas campestris pathovar campestris (Xcc) is influenced by a number of. Among them, Xanthomonas campestris is the most dominant species with at least .. Identification of other genes encoding for biofilm formation/dispersal and.

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Studies on xanthan production from Xanthomonas campestris.

The dashed arrow indicates basal signal generation or no signal flow. Genetic and molecular analysis of a cluster of rpf genes involved in positive regulation of synthesis of extracellar enzymes and polysaccharide in Xanthomonas campestris pv.

The rpfF mutants show severely reduced motility, decreased production of extracellular protease, decreased tolerance to a range of antibiotics and heavy metals, and form cell aggregates Fouhy et al. Subsequently, it was found that the protease production in the mutant of the rpfF gene, which encodes a putative enoyl CoA hydratase, was restored by cocultivation in proximity to Xcc wild-type strains, suggesting that Xcc wild-type strains could produce a diffusible signal factor DSF Barber et al.

The DSF signal, originally identified in Xccrepresents a novel class of the QS signal, that appears to be widely conserved in a range of bacterial species. QS is one of the sophisticated mechanisms of cell—cell communications, by which bacteria count their own number by producing, detecting, and responding to the accumulation of signaling molecules that they export into their environment for reviews, see Whitehead et al.

References Publications referenced by this paper. These phenotypes are puzzling, given that the transcriptional expression of clp is upregulated by DSF. It is similarly intriguing that only rpfG and pdeA seem to regulate biofilm formation and only rpfG controls motility under the conditions tested Ryan et al.

Once inside the plant, Xcc colonizes the vascular system where it produces an extracellular polysaccharide EPS called xanthan, which can obstruct the xylem vessels, causing tissue necrosis and severe leaf wilting Williams, ; Onsando, Clp upregulates transcription of engA gene encoding a virulence factor in Xanthomonas campestris by direct binding to the upstream tandem Clp sites. In wild-type strain XC1, deletion of rpfF results in formation of cell aggregates comprising a few dozens to a few hundred cells, whereas deletion of clp alone does not affect DSF production, not does it cause the formation of cell aggregates He et al.


Interestingly, two groups of Gram-negative bacterial QS signals, i. Regulation of quorum sensing in Pseudomonas. Further analysis reveals that DSF may autoregulate its biosynthesis through a novel posttranslational mechanism involving RpfC—RpfF interaction. Third, Xcc may be able to sense various cues of the environment and integrate the signal inputs by changing the cellular content of cyclic-di-GMP, and thus to modulate the bacterial physiology and virulence.

Biofilm formation and dispersal in Xanthomonas campestris.

Measurement of gene expression levels has been performed using an oligonucleotide microarray based on the genome sequence of Xcc strain ATCC He et al. Overexpression of a short peptide of aa within the receiver domain is sufficient to block the DSF production by the rpfC deletion mutant He et al. Within this family, the Crp of E.

As the sensitivity of downstream regulatory systems to the change of cyclic-di-GMP or related nucleotides level may differ, these subtle differences would be translated to acmpestris bacterial responses to different environmental cues. Genome annotation of Xcc strains ATCC and leads to prediction of and genes, respectively da Silva et al.

Biofilm formation and dispersal in Xanthomonas campestris.

Identification, timing, and signal specificity of Pseudomonas aeruginosa quorum-controlled genes. The information was summarized from the following references: The availability of the Xcc genome sequence and advancement of microarray technology have greatly facilitated the determination of the scope of genes and biological functions regulated by the DSF signal.

DNA binding specificity and sequence of Xanthomonas campestris catabolite gene activator protein-like protein. QS, in which bacterial xanthomonae communicate by means of small signal molecules, plays essential roles in the synchronization of gene expression and functional coordination among bacterial communities.

Structure of a complex of catabolite gene activator protein and cyclic AMP refined at 2.

Type III protein secretion systems in bacterial pathogens of animals and plants. Three cdg operons control cellular turnover of cyclic-di-GMP in Acetobacter xylinum.

Previously we demonstrated that the post-transcriptional regulator RsmA exerts a negative regulatory influence on biofilm formation in Xcc. The contribution of each of these proteins to virulence, extracellular enzyme synthesis, and biofilm formation has been investigated using a panel of mutants Ryan et al.

Moreover, microarray analysis shows that the DSF regulon and the Clp regulon are largely overlapping with similar expression patterns He et al. At present, two chemically similar AI-2 signals have been identified in Vibrio harveyi and Salmonella typhimuriumrespectively.


In addition, the transcriptional expression of several DSF-regulated genes He et al. In trans expression of the HD-GYP domain of RpfG alone in the null mutants of RpfG restores the production of EPS and extracellular enzymes to a level close to the wild-type strain, whereas expression of the receiver domain alone has no effect He, ; Ryan et al.

Comparison of the biological activities of a range of DSF derivatives has led to identification of a few key structural features that determine the signaling activity. Consistently, exogenous addition of DSF at a physically relevant concentration to the rpfF deletion mutants grown in rich medium restores the wild-type planktonic growth mode He et al. A cAMP receptor protein regulated cell—cell communication system mediates expression of a FecA homologue in Stenotrophomonas maltophilia.

Holger SondermannNicholas J. Email alerts New issue alert. Quorum sensing modulation of a putative glycosyltransferase gene cluster essential for Xanthomonas campestris biofilm formation. Laboratory-scale production of polysaccharides by species of Xanthomonas.

Salmonella typhimurium recognizes a chemically distinct form of the bacterial quorum-sensing signal AI Moreover, evidence is emerging that the DSF QS system is conserved in a range of plant and human bacterial pathogens. Its function in the DSF-signaling system remains unclear.

Booming research on QS since the s has led to identification of several types of bacterial QS signals Fig. Most proteins or enzymes encoded by these 86 genes belong to the following functional groups: The HD domain defines a new superfamily of metal-dependent phosphohydrolases.

Showing of 33 references. Among the two fatty acid metabolism enzymes, RpfF is particularly interesting as its expression in a non-DSF-producing bacterium, such as E. Waters Journal of bacteriology The bacterium has a single polar flagellum, is positive in catalase activity and hydrogen sulfide reaction, oxidase negative, and does not produce nitrate or indole Onsando, The solid arrow indicates the demonstrated or predicted directed protein—protein interaction or directed signal modulation.

Pathogenicity determinants and global regulation of pathogenicity of Xanthomonas campestris pv. Third, site-directed mutagenesis of the three conserved amino acid residues involved in phosphorelay has no effect on DSF production He et al.