Abstract:[Objective] The PcoI/PcoR quorum-sensing (QS) system in Pseudomonas fluorescens 2P24, important for biofilm formation and plant root colonization, was influenced by multiple upstream regulatory elements. In this study, the effect of the gidA gene on QS system was studied by genetic analysis. [Methods] The transcriptional reporter of pcoI gene on plasmid p970km-pcoIp was used to monitor the pcoI expression in the wild type strain 2P24 and its gidA gene mutant. Agrobacterium tumefaciens NTL4 (pZLR4) was used as the reporter strain to detect QS signal molecule N-acyl-homoserine lactone (AHL) production. [Results] Mutation of the gidA gene in strain 2P24 did not influence its swimming capacity, but significantly decreased pcoI transcription and AHL production. Furthermore, the biofilm formation and the colonization on the wheat rhizosphere and tips in both the gnotobiotic and natural soil were remarkably reduced in the gidA gene mutant compared with the wild type and the complementary strain. Although the gidA mutation in strain 2P24 did not affect the bacterial growth in the rich medium (LB), it significantly affected the utilization of multiple carbon sources in the minimal medium, including glucose, sucrose, fructose, glycerol, galactose, arabinose, mannose, xylose and sorbitol. [Conclusion] These results suggest that GidA function as a globle regulatory element influenced the PcoI/PcoR QS system, biofilm formation, colonization ability and carbon source utilization in P. fluorescens 2P24.
