SprI/SprR Quorum Sensing System ofSerratia proteamaculans94

Abstract

In this study, we investigated the quorum sensing (QS) regulatory system of the psychrotrophic strainSerratia proteamaculans94 isolated from spoiled refrigerated meat. The strain produced severalN-acyl-L-homoserine-lactone (AHL) QS signal molecules, withN-(3-oxo-hexanoyl)-L-homoserine lactone andN-(3-hydroxy-hexanoyl)-L-homoserine lactone as two main types. ThesprIandsprRgenes encoding an AHL synthase and a receptor regulatory protein, respectively, were cloned and sequenced. Analysis of their nucleotide sequence showed that these genes were transcribed convergently and that their reading frames partly overlapped by 23 bp in the terminal regions. The genes were highly similar to theluxI/luxR-type QS genes of other Gram-negative bacteria. Anspr-box (analog of thelux-box) was identified upstream of thesprRgene and found to be overlapped with the sequence of −10 sequence site in the promoter region of this gene. Inactivation of thesprIgene led to the absence of AHL synthesis, chitinolytic activity, and swimming motility; decrease of extracellular proteolytic activity; affected the cellular fatty acid composition; and reduced suppression of the fungal plant pathogen mycelium growth by volatile compounds emitted by strainS. proteamaculans94. The data obtained demonstrated the important role of the QS system in the regulation of cellular processes inS. proteamaculans94.