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Integrated regulation of acetoin fermentation by quorum sensing and pH in Serratia plymuthica RVH1.

ABSTRACT: During fermentation of sugars, a number of bacterial species are able to switch from mixed acid production to acetoin and 2,3-butanediol production in order to avoid lethal acidification of their environment, although the regulation of this switch is only poorly understood. In this study, we report the identification of the budAB structural operon, involved in acetoin production in Serratia plymuthica RVH1, and its activation by a LysR-type regulator encoded by budR, immediately upstream of this operon. In addition, the regulation of budR transcription was elucidated and found to be subject to negative control by BudR itself and to positive control by external stimuli such as N-(3-oxohexanoyl)-L-homoserine lactone (OHHL) quorum sensing signaling molecules and acetate. Interestingly, however, we observed that induction of budR transcription by OHHL or acetate did not require BudR, indicating the involvement of additional regulatory factors in relaying these environmental signals to the budR promoter.

SUBMITTER: Moons P

PROVIDER: S-EPMC3126459 | biostudies-literature | 2011 May

REPOSITORIES: biostudies-literature

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Integrated regulation of acetoin fermentation by quorum sensing and pH in Serratia plymuthica RVH1.

Moons Pieter P Van Houdt Rob R Vivijs Bram B Michiels Chris W CW Aertsen Abram A

Applied and environmental microbiology 20110325 10

During fermentation of sugars, a number of bacterial species are able to switch from mixed acid production to acetoin and 2,3-butanediol production in order to avoid lethal acidification of their environment, although the regulation of this switch is only poorly understood. In this study, we report the identification of the budAB structural operon, involved in acetoin production in Serratia plymuthica RVH1, and its activation by a LysR-type regulator encoded by budR, immediately upstream of this ...[more]

PMID: 21441339

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Project description:BackgroundN-acylhomoserine lactone (AHL)-based quorum sensing (QS) systems have been described in many plant-associated Gram-negative bacteria to control certain beneficial phenotypic traits, such as production of biocontrol factors and plant growth promotion. However, the role of AHL-mediated signalling in the endophytic strains of plant-associated Serratia is still poorly understood. An endophytic Serratia sp. G3 with biocontrol potential and high levels of AHL signal production was isolated from the stems of wheat and the role of QS in this isolate was determined.ResultsStrain G3 classified as Serratia plymuthica based on 16S rRNA was subjected to phylogenetic analysis. Using primers to conserved sequences of luxIR homologues from the Serratia genus, splIR and spsIR from the chromosome of strain G3 were cloned and sequenced. AHL profiles from strain G3 and Escherichia coli DH5α expressing splI or spsI from recombinant plasmids were identified by liquid chromatography-tandem mass spectrometry. This revealed that the most abundant AHL signals produced by SplI in E. coli were N-3-oxo-hexanoylhomoserine lactone (3-oxo-C6-HSL), N-3-oxo-heptanoylhomoserine lactone (3-oxo-C7-HSL), N-3-hydroxy-hexanoylhomoserine lactone (3-hydroxy-C6-HSL), N-hexanoylhomoserine lactone (C6-HSL), and N-heptanoyl homoserine lactone (C7-HSL); whereas SpsI was primarily responsible for the synthesis of N-butyrylhomoserine lactone (C4-HSL) and N-pentanoylhomoserine lactone (C5-HSL). Furthermore, a quorum quenching analysis by heterologous expression of the Bacillus A24 AiiA lactonase in strain G3 enabled the identification of the AHL-regulated biocontrol-related traits. Depletion of AHLs with this lactonase resulted in altered adhesion and biofilm formation using a microtiter plate assay and flow cells coupled with confocal laser scanning microscopy respectively. This was different from the closely related S. plymuthica strains HRO-C48 and RVH1, where biofilm formation for both strains is AHL-independent. In addition, QS in G3 positively regulated antifungal activity, production of exoenzymes, but negatively regulated production of indol-3-acetic acid (IAA), which is in agreement with previous reports in strain HRO-C48. However, in contrast to HRO-C48, swimming motility was not controlled by AHL-mediated QS.ConclusionsThis is the first report of the characterisation of two AHL-based quorum sensing systems in the same isolate of the genus Serratia. Our results show that the QS network is involved in the global regulation of biocontrol-related traits in the endophytic strain G3. However, although free-living and endophytic S. plymuthica share some conservation on QS phenotypic regulation, the control of motility and biofilm formation seems to be strain-specific and possible linked to the life-style of this organism.

Dataset Information

Integrated regulation of acetoin fermentation by quorum sensing and pH in Serratia plymuthica RVH1.

Publications

Integrated regulation of acetoin fermentation by quorum sensing and pH in Serratia plymuthica RVH1.

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