Bioinformatics Analysis of NprR-NprX Quorum-Sensing System of Bacillus thuringiensis Isolates from the Papaloapan Region, Oaxaca-Mexico

Abstract

Quorum sensing is a chemical communication process that bacteria use to regulate collective be haviors. In Gram-positive bacteria, oligopeptides (called autoinducers) are the signaling mole cules to elicit quorum sensing. In Bacillus thuringiensis, NprR is a transcriptional regulator whose activity depends on the NprX signalling peptide. Bacillus thuringiensis is closely related to Bacillus cereus and Bacillus anthracis. The principal difference between them is that Bacillus thuringiensis is the only one that produced Cry protein. The aim of this study is to explore the relation of nprR and 16S rRNA genes in Bacillus thuringiensis. Phylogenetic trees of nucleotide sequences of nprR and 16S rRNA genes were built. Sequences of fourteen new isolates from Papaloapan region were included in those phylogenetic trees. In order to identify the isolates, a simple and fast methodol ogy considering the Cry protein formation was used. The 16S rRNA phylogenetic tree allows iden tify eight isolates as Bacillus thuringiensis and the others as Bacillus spp. The nprR phylogenetic tree does not match with the 16S rRNA phylogenetic tree. This confirms that nprR is not a molecu lar marker for evolution. Most of the new isolates have the same NprR sequence (WTSDIVG). How- ever, the SKPDIVG is the most common NprR sequence in thuringiensis species.