Abstract
Quorum sensing is a chemical communication process that bacteria use to regulate collective behaviors. In Gram-positive bacteria, oligopeptides (called autoinducers) are the signaling molecules 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 methodology considering the Cry protein formation was used. The 16S rRNA phylogenetic tree allows identify 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 molecular marker for evolution. Most of the new isolates have the same NprR sequence (WTSDIVG). However, the SKPDIVG is the most common NprR sequence in thuringiensis species.
Highlights
Several bacterial species use the Quorum Sensing (QS, cell-cell communication) to coordinate their behavior as a whole community [1]
The isolation method results show that the phase contrast microscopy strategy is not enough for B. thuringiensis isolation
The phylogenic analysis of the 16S rRNA gene from 30 isolates from the Papalopan region 24 isolates was identified as B. thuringiensis while 6 of them were unidentified (Table 2)
Summary
Several bacterial species use the Quorum Sensing (QS, cell-cell communication) to coordinate their behavior as a whole community [1]. In Gram-positive bacteria, the signaling molecules are mostly small secreted peptides that are actively released into the extracellular environment [2]. Genome analysis indicated that genes encoding a putative regulator (NprR) and a putative signaling peptide (NprX or NprRB) were found upstream from nprA in the bacteria of the Bacillus cereus (B. cereus) group [3] [4]. These genes encode for a receptor and for a small protein. The small protein has a putative signal sequence used in the export pathway and a secreted domain [5]. The NprR-NprX system was found in all the species of B. cereus group, where 31 different NprR polypeptide sequences were identified [3]
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