Cloning and preliminary identification of SptR, a LuxR-like regulator from Serratia plymuthica

Abstract

N-acylhomoserine lactone (AHL)-mediated Quorum sensing (QS) allows bacterial populations to communicate via the exchange of diffusible signals to coordinate gene expression and control adaptive behaviors in response to cell density in Gram-negative bacteria. Two luxIR-like QS systems splIR and spsIR have been characterized in an endophytic strain G3 of Serratia plymuthica. Here we reported a third LuxR homolog, SptR for better understanding the QS network by strain G3. Firstly, cloning and sequencing of a sptR gene was performed using PCR; phylogenetic analysis revealed that SptR was not closely correlated to other members of LuxR-family protein in Serratia, but clustered into one clade with LuxR-family members from Enterobacter cloacae SCF1 and Erwinia tasmaniensis Et1/99 sharing a more common ancestor. Further mutational analysis of biocontrol-related phenotypes demonstrated that SptR served as a positive regulator to control production of exenzymes, as well as swimming motility and biofilm formation contrary to most LuxR homologs from Serratia as repressor. However, no significant impact on production of auxin indole-3-acetic acid (IAA) and antagonistic ability was observed. The results paved the way for further studies of the complex QS network and regulatory mechanisms involved in fine tuning of beneficial bacteria-plant interactions by S. plymuthica.

Biosynthesis of the acetyl‐CoA carboxylase‐inhibiting antibiotic, andrimid in Serratia is regulated by Hfq and the LysR‐type transcriptional regulator, AdmX

“…) and so we investigated whether quorum sensing (QS) could be regulating andrimid production. A153 carries sptI, sptR , splR and spsR genes encoding LuxI‐ and LuxR‐type proteins very similar to those of the three QS systems identified in the taxonomically related rhizobacterium, S. plymuthica G3 (Liu et al ., ; Duan et al ., ). However mutations in each of these four genes in A153 had no observable impacts on antibacterial activity (not shown).…”

Biosynthesis of the antifungal haterumalide, oocydin A, in Serratia, and its regulation by quorum sensing, RpoS and Hfq

“…The highest levels of transcription of the ooc gene cluster occurred at higher cell densities suggesting that expression could be under QS control. Analysis of the genome sequence of S. plymuthica A153 revealed a candidate QS locus, SptIR and two orphan LuxR encoding genes, splR and spsR , all highly homologous to the luxI - and luxR -type genes encoded by the three QS loci present in S. plymuthica G3 (Liu et al ., 2011 ; Duan et al ., 2012 ). However, we were unable to detect the production of QS signalling molecules in A153 using the biosensor strains Chromobacterium violaceum CV026 (McClean et al ., 1997 ) and Serratia SP19 (Poulter et al ., 2010 ) (not shown).…”