Controlled synthesis of the DSF cell–cell signal is required for biofilm formation and virulence in <i>Xanthomonas campestris</i>

Torres, Pablo; Malamud, Florencia; Rigano, Luciano A.; Russo, Daniela M.; Maraño, María Rosa; Castagnaro, Atilio Pedro; Zorreguieta, Ángeles; Bouarab, Kamal; Dow, J. Maxwell; Vojnov, Adrián Alberto

doi:10.1111/j.1462-2920.2007.01332.x

Cited by 94 publications

(93 citation statements)

References 23 publications

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“…We used chambered coverslides, whereby the base of the culture chamber forms a coverslip, to visualize biofilm formation, as this allowed us to visualize aggregates as they sedimented. Chambered coverslides have also been used in studies of R. leguminosarum [11], S. meliloti [46] and X. campestris [47] biofilms. We found that the exoS mutant forms an inhomogeneous structure, consisting of interlinked aggregates separated by gaps that are characteristic of the 'water channels' described in many biofilms.…”

Section: Discussionmentioning

confidence: 99%

Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

Dorken

Ferguson

French

et al. 2012

J. R. Soc. Interface.

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In bacteria, the production of exopolysaccharides-polysaccharides secreted by the cells into their growth medium-is integral to the formation of aggregates and biofilms. These exopolysaccharides often form part of a matrix that holds the cells together. Investigating the bacterium Sinorhizobium meliloti, we found that a mutant that overproduces the exopolysaccharide succinoglycan showed enhanced aggregation, resulting in phase separation of the cultures. However, the aggregates did not appear to be covered in polysaccharides. Succinoglycan purified from cultures was applied to different concentrations of cells, and observation of the phase behaviour showed that the limiting polymer concentration for aggregation and phase separation to occur decreased with increasing cell concentration, suggesting a 'crowding mechanism' was occurring. We suggest that, as found in colloidal dispersions, the presence of a non-adsorbing polymer in the form of the exopolysaccharide succinoglycan drives aggregation of S. meliloti by depletion attraction. This force leads to self-organization of the bacteria into small clusters of laterally aligned cells, and, furthermore, leads to aggregates clustering into biofilm-like structures on a surface.

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Section: Discussionmentioning

confidence: 99%

Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

Dorken

Ferguson

French

et al. 2012

J. R. Soc. Interface.

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“…campestris. It can enhance the susceptibility of host plants by suppressing defense responses such as callose formation (72) and can contribute to biofilm formation (18,61) and bacterial resistance against host defenses. It may also serve to mask bacterial cells to prevent recognition by the host and to enable colonization of host tissues (1).…”

Section: Discussionmentioning

confidence: 99%

An Adenosine Kinase Exists inXanthomonas campestrisPathovar campestris and Is Involved in Extracellular Polysaccharide Production, Cell Motility, and Virulence

Yong-qin

et al. 2009

J Bacteriol

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Adenosine kinase (ADK) is a purine salvage enzyme and a typical housekeeping enzyme in eukaryotes which catalyzes the phosphorylation of adenosine to form AMP. Since prokaryotes synthesize purines de novo and no endogenous ADK activity is detectable in Escherichia coli, ADK has long been considered to be rare in bacteria. To date, only two prokaryotes, both of which are gram-positive bacteria, have been reported to contain ADK. Here we report that the gram-negative bacterium Xanthomonas campestris pathovar campestris, the causal agent of black rot of crucifers, possesses a gene (designated adk Xcc ) encoding an ADK (named ADK Xcc ), and we demonstrate genetically that the ADK Xcc is involved in extracellular polysaccharide (EPS) production, cell motility, and pathogenicity of X. campestris pv. campestris. adk Xcc was overexpressed as a His 6 -tagged protein in E. coli, and the purified His 6 -tagged protein exhibited ADK activity. Mutation of adk Xcc did not affect bacterial growth in rich and minimal media but led to an accumulation of intracellular adenosine and diminutions of intracellular ADK activity and ATP level, as well as EPS. The adk Xcc mutant displayed significant reductions in bacterial growth and virulence in the host plant.

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“…campestris (Xcc) (Rigano et al, 2007a;Torres et al, 2007). Synthesis and perception of DSF require proteins coded in the rpf cluster (for regulation of pathogenicity factors).…”

Section: Introductionmentioning

confidence: 99%

“…RpfF directs DSF synthesis whereas RpfC is involved in DSF perception (Barber et al, 1997;Slater et al, 2000). Mutants in the rpfF (DSF-minus) and rpfC (DSF overproducer) genes in Xcc can only form unstructured arrangements of bacteria (Torres et al, 2007). Synthesis of xanthan is directed by genes from the gum operon (da Silva et al, 2002), which is highly conserved in Xanthomonas spp.…”

Section: Introductionmentioning

confidence: 99%

The Xanthomonas axonopodis pv. citri flagellum is required for mature biofilm and canker development

et al. 2011

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The Xanthomonas axonopodis pv. citri flagellum is required for mature biofilm and canker development Xanthomonas axonopodis pv. citri (Xac) is the causative agent of citrus canker. This bacterium develops a characteristic biofilm on both biotic and abiotic surfaces. To evaluate the participation of the single flagellum of Xac in biofilm formation, mutants in the fliC (flagellin) and the flgE (hook) genes were generated. Swimming motility, assessed on 0.25 % agar plates, was markedly reduced in fliC and flgE mutants. However, the fliC and flgE mutants exhibited a flagellarindependent surface translocation on 0.5 % agar plates. Mutation of either the rpfF or the rpfC gene, which both encode proteins involved in cell-cell signalling mediated by diffusible signal factor (DSF), led to a reduction in both flagellar-dependent and flagellar-independent surface translocation, indicating a regulatory role for DSF in both types of motility. Confocal laser scanning microscopy of biofilms produced in static culture demonstrated that the flagellum is also involved in the formation of mushroom-shaped structures and water channels, and in the dispersion of biofilms. The presence of the flagellum was required for mature biofilm development on lemon leaf surfaces. The absence of flagellin produced a slight reduction in Xac pathogenicity and this reduction was more severe when the complete flagellum structure was absent.

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Controlled synthesis of the DSF cell–cell signal is required for biofilm formation and virulence in Xanthomonas campestris

Cited by 94 publications

References 23 publications

Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

Aggregation by depletion attraction in cultures of bacteria producing exopolysaccharide

An Adenosine Kinase Exists inXanthomonas campestrisPathovar campestris and Is Involved in Extracellular Polysaccharide Production, Cell Motility, and Virulence

The Xanthomonas axonopodis pv. citri flagellum is required for mature biofilm and canker development

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