Quorum Sensing in the Endophytic Strain of Serratia

An international team of scientists from Jiangsu University (Zhenjiang, Jiangsu Province, China), the University of Nottingham (Nottingham, United Kingdom), and Shandong Agricultural University (Taian, China) has used liquid chromatography–tandem mass spectrometry (LC–MS-MS) to examine the role of quorum sensing on an endophytic strain of Serratia.

Endophytic bacteria live in plant tissues without posing a significant threat to the plant, and can be beneficial by promoting plant growth or functioning as a biocontrol agent. Quorum sensing (QS) controls gene expression within bacterial gene regulatory networks. According to the research team, these QS systems are involved in various physiological processes within bacteria, including bioluminescence, conjugation, symbiosis, virulence, and biofilm formation. To further understand the role of N-acylhomoserine lactone (AHL)-based QS systems in the endophytic strain of Serratia, the team isolated strain G3 Serratia from the stems of wheat.

Strain G3 Serratia was subject to phylogenetic analysis, which allowed the team to identify and characterize two luxIR homolog genes, splIR and spsIR. Conducting LC–MS-MS analysis, the team examined AHL profiles derived from strain G3 and Escherichia coli DH5a expressing splIR or spsIR from recombinant plasmids and identified the most abundant signals produced by splIR and spsIR.

This is the first report of the characterization of two AHL-based quorum sensing systems in the same isolate of the genus Serratia. The team concluded that the QS network is involved in global regulation of biocontrol-related traits, especially antifungal activity, adhesion, and biofilm formation, some of which are strain specific, in the genus of Serratia. The researchers hope to further examine the interplay between the QS systems splIR and spsIR, and their integration into complex regulatory networks.

The team published its findings in the February 1, 2011, issue of BMC Microbiology.