LuxS Sequence Alignment of Different Gram-Negative Bacteria, is it Conserved?

Abstract

Background: Quorum sensing is a mechanism by which bacteria can communicate with each other’s using chemical signals termed autoinducers. Each single cell can detect the concentration of those signals in its surrounding. As the concentration of those signals reaches a threshold, the bacterial population is then ready to make their decision. Quorum sensing has been reported to regulate many biological processes like secondary metabolites production, biofilm formation, virulence, symbiosis, and dormancy. Autoinducer-2 (AI-2) is an important quorum sensing signal involved in inter-species communication. It is synthesized by the enzyme LuxS. In this work, we are trying to find out how much is the similarity of LuxS sequence between different Gram-negatives. This might lead to a better understanding of its evolutionary lineage and conservatively Methods: LuxS DNA complete coding sequence from Escherichia coli (K88, O17:K52:H18, O7:K1, K-12, O83:H1, O104:H4), Klebsiella pneumoniae, Salmonella typhimurium, Yersinia pestis, Dickeya dadantii, Citrobacter freundii, Vibrio fischeri, Haemophilus influenza, Shewanella oneidensis and Aeromonas hydrophila was obtained from Genebank. DNA sequence analysis was carried out by means of multiple sequence alignment using EMBOSS Clustal Omega and aligned using default setting at times with all mentioned strains and, at other times only with the E. coli strains Results: Pairwise sequence alignment data showed varied areas of similarity between different strains even within same species. Percent identity matrix showed a high percentage of similarity between two different species (Salmonella typhimurium and E. coli, 86%) and within the same species (E. coli K88 and O17:K52:H18, 99%). Also, it showed a very low percent of similarity (Dickeya dadantii and E. coli O83:H1, 33%) and only 42% between E. coli K-12 and O83:H1. The dendogram showed unexpected evolutionary pathway of LuxS of which this sequence in E. coli K88 and O104:H4 is closer to S. typhimurium much more than to the other E. coli strains Conclusions: LuxS sequence evolved dramatically even within the same species. This might reflect the effect of quorum sensing interaction effect in different environments which might be a case of convergent evolution, and the communication specificity within the same species and also with different species