Abstract
Quorum sensing is a well-studied cell-to-cell communication method that involves a cell-density dependent regulation of genes expression mediated by signalling molecules. In this study, a bacterium isolated from a plant material compost pile was found to possess quorum sensing activity based on bioassay screening. Isolate YL12 was identified using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry and molecular typing using rpoD gene which identified the isolate as Aeromonas caviae. High resolution tandem mass spectrometry was subsequently employed to identify the N-acyl homoserine lactone profile of Aeromonas caviae YL12 and confirmed that this isolate produced two short chain N-acyl homoserine lactones, namely C4-HSL and C6, and the production was observed to be cell density-dependent. Using the thin layer chromatography (TLC) bioassay, both AHLs were found to activate C. violaceum CV026, whereas only C6-HSL was revealed to induce bioluminescence expression of E. coli [pSB401]. The data presented in this study will be the leading steps in understanding the role of quorum sensing in Aeromonas caviae strain YL12.
Highlights
Composting is an aerobic process, which is mainly carried out by a rapid succession of mixed microbial populations, mainly constituted by bacteria and fungi
80 strains of bacteria were isolated from the compost suspension and all of the strains were preliminarily screened for acyl homoserine lactone (AHL) production by cross-streaking with C. violaceum CV026 as biosensor
C. violaceum CV026 is an AHL biosensor that was subjected to mini-Tn5 transposon mutagenesis which result in a mutation that is defective in production of AHL but retain the capability of producing violacein, a water-insoluble purple pigment, when exogenous short chain AHLs are detected [17]
Summary
Composting is an aerobic process, which is mainly carried out by a rapid succession of mixed microbial populations, mainly constituted by bacteria and fungi. A wide range of bacteria has been found in different compost environments, which includes species of Pseudomonas, Klebsiella, and Bacillus [2,3]. The roles of microflora with quorum sensing (QS) activity in composting environment have not been investigated in depth. Studies conducted have discovered that quorum sensing plays essential role in controlling expression of advantageous bacterial phenotype which complements to the environmental conditions. Aeromonas caviae is a mesophilic species of the genus Aeromonas and it is commonly known as an environmental strain that occur ubiquitously in aquatic environments. Besides its role as a clinical strain, A. caviae was discovered to be a potential biocontrol agent against fungal pathogens with its chitinolytic activity [16]. We report the identification of a QS A. caviae strain isolated from compost
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