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The Gac regulon of P seudomonas fluorescens SBW 25
Author(s) -
Cheng Xu,
Bruijn Irene,
Voort Menno,
Loper Joyce E.,
Raaijmakers Jos M.
Publication year - 2013
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12061
Subject(s) - mutant , regulon , swarming motility , pseudomonas fluorescens , biology , gene , operon , transcriptome , siderophore , complementation , microbiology and biotechnology , biochemistry , genetics , bacteria , virulence , gene expression , quorum sensing
Summary Transcriptome analysis of P seudomonas fluorescens SBW 25 showed that 702 genes were differentially regulated in a gacS :: Tn 5 mutant, with 300 and 402 genes up‐ and downregulated respectively. Similar to the Gac regulon of other P seudomonas species, genes involved in motility, biofilm formation, siderophore biosynthesis and oxidative stress were differentially regulated in the gacS mutant of SBW 25. Our analysis also revealed, for the first time, that transcription of 19 rhizosphere‐induced genes and of genes involved in type II secretion, (exo)polysaccharide and pectate lyase biosynthesis, twitching motility and an orphan non‐ribosomal peptide synthetase ( NRPS ) were significantly affected in the gacS mutant. Furthermore, the gacS mutant inhibited growth of oomycete, fungal and bacterial pathogens significantly more than wild type SBW 25. Since RP ‐ HPLC analysis did not reveal any potential candidate metabolites, we focused on the Gac ‐regulated orphan NRPS gene cluster that was predicted to encode an eight‐amino‐acid ornicorrugatin‐like peptide. Site‐directed mutagenesis indicated that the encoded peptide is not involved in the enhanced antimicrobial activity of the gacS mutant but may function as a siderophore. Collectively, this genome‐wide analysis revealed that a mutation in the GacS / A two‐component regulatory system causes major transcriptional changes in SBW 25 and significantly enhances its antimicrobial activities by yet unknown mechanisms.