Abstract
The process of intercellular communication among bacteria, termed quorum sensing (QS), is mediated by small diffusible molecules known as the autoinducers. QS allows the population to react to the change of cell density in unison, in processes such as biofilm formation, plasmid conjugation, virulence, motility and root nodulation. In Gram-negative proteobacteria, N-acyl homoserine lactone (AHL) is the common “language” to coordinate gene expression. This signaling molecule is usually synthesized by LuxI-type proteins. We have previously discovered that a rare bacterium, Cedecea neteri, exhibits AHL-type QS activity. With information generated from genome sequencing, we have identified the luxIR gene pair responsible for AHL-type QS and named it cneIR. In this study, we have cloned and expressed the 636 bp luxI homolog in an Escherichia coli host for further characterization. Our findings show that E. coli harboring cneI produced the same AHL profile as the wild type C. neteri, with the synthesis of AHL known as N-butyryl-homoserine lactone. This 25 kDa LuxI homolog shares high similarity with other AHL synthases from closely related species. This work is the first documentation of molecular cloning and characterization of luxI homolog from C. neteri.
Highlights
Bacteria communicate with each other through a phenomenon called quorum sensing (QS), which enables them to detect the cellular density of the population, directing proper genotypic and phenotypic adaptations (Bassler and Losick, 2006)
We demonstrated that C. neteri SSMD04 exhibits QS activity using biosensors and hypothesized that QS potentially plays a role in the regulation of its virulence and lipolytic pathways
The protein sequence of CneI was searched against the NCBI database using BLAST and it was found to have a high degree of similarity with several protein sequences
Summary
Bacteria communicate with each other through a phenomenon called quorum sensing (QS), which enables them to detect the cellular density of the population, directing proper genotypic and phenotypic adaptations (Bassler and Losick, 2006). This is achieved through the synthesis, release, detection, and response to small diffusible signaling molecules called the autoinducers (Schauder and Bassler, 2001). The length of the acyl side chain ranging from four to eighteen carbon atoms, the saturation level of the side chain, as well as the substitution group at the third carbon atom by oxo or hydroxyl group contribute to the variation in AHL structures (Whitehead et al, 2001; Williams et al, 2007)
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