Three independent signalling pathways repress motility in Pseudomonas fluorescens F113.
Bottom Line: In order to identify genes and pathways implicated in motility repression, we have used generalized mutagenesis with transposons.Epistasis analysis has shown that the pathways defined by each of these genes are independent, because double and triple mutants show an additive phenotype.Furthermore, GacS, SadB and WspR act at different levels.
Affiliation: Departamento de Biología. Universidad Autónoma de Madrid. c/Darwin, 2, 28049 Madrid, Spain.Show MeSH
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Mentions: To determine that the swimming motility phenotype of both mutants was linked to the transposon insertion, the mutants were reconstructed by insertional mutagenesis using homologous recombination. Reconstructed mutants showed the same hypermotile phenotype (Fig. 1) than the transposon tagged mutants and were used for further characterization. Wild‐type F113 produced a 10.25 ± 0.5 mm diameter halo after 18 h. The gacS, sadB and wspR mutants produced haloes of 13.25 ± 0.5, 15.5 ± 1 and 16 ± 0.8 mm. All the mutants produced statistically larger haloes than F113 (P < 0.05). No statistical difference was observed between gacS and sadB or sadB and wspR. However, wspR produced haloes significantly larger than gacS (P < 0.05). The mutants were also tested for swarming motility and biofilm formation. Conversely to the wild‐type strain, both mutants were able to swarm (Fig. 2) and were affected in biofilm formation on abiotic surfaces (not shown). Therefore, besides swimming motility, shown here, SadB and the Wsp system appear to be implicated in the regulation of these phenotypes in P. fluorescens, as has been described in other pseudomonads.
Affiliation: Departamento de Biología. Universidad Autónoma de Madrid. c/Darwin, 2, 28049 Madrid, Spain.