Genomic and molecular characterization of a novel quorum sensing molecule in Bacillus licheniformis

Elham Esmaeilishirazifard,Sterghios A Moschos,Daniela De Vizio,Tajalli Keshavarz

doi:10.1186/s13568-017-0381-6

Elham Esmaeilishirazifard, Sterghios A Moschos + Show 2 more

Open Access

https://doi.org/10.1186/s13568-017-0381-6

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Abstract

Quorum sensing molecules (QSMs) are involved in the regulation of complicated processes helping bacterial populations respond to changes in their cell-density. Although the QS gene cluster (comQXPA) has been identified in the genome sequence of some bacilli, the QS system B. licheniformis has not been investigated in detail, and its QSM (ComX pheromone) has not been identified. Given the importance of this antagonistic bacterium as an industrial workhorse, this study was aimed to elucidate B. licheniformis NCIMB-8874 QS. The results obtained from bioinformatics studies on the whole genome sequence of this strain confirmed the presence of essential quorum sensing-related genes. Although polymorphism was verified in three proteins of this cluster, ComQ, precursor-ComX and ComP, the transcription factor ComA was confirmed as the most conserved protein. The cell–cell communication of B. licheniformis NCIMB-8874 was investigated through further elucidation of the ComX pheromone as 13-amino acid peptide. The peptide sequence of the pheromone has been described through biochemical characterisation.

Highlights

The first evidence of microbial cell–cell communication was reported by Tomasz and Beiser in 1965, when they suggested that a hormone-like extracellular product regulated competence in Streptococcus pneumoniae (Tomasz and Beiser 1965)
Polymorphism of the quorum sensing locus at the protein level To evaluate the presence of the comQXPA locus in the draft assembly of B. licheniformis protein, homologues of other bacilli were investigated after annotating the B. licheniformis NCIMB 8874 assembled sequence data through “IonGap Annotation Service” and aligning amino acid sequences of comQXPA cluster from this strain with homologous proteins from other Bacilli using “Clustal Omega” (Stark et al 2010)
The alignment of B. licheniformis NCIMB 8874 ComQ with other homologues showed that the highest degree of identity appeared in other B. licheniformis strains such as 9945A, F11 and ATCC 14580

Summary

Introduction

The first evidence of microbial cell–cell communication was reported by Tomasz and Beiser in 1965, when they suggested that a hormone-like extracellular product regulated competence in Streptococcus pneumoniae (Tomasz and Beiser 1965). Later on researchers found that the product was a peptide acting as a common signal in cell–cell communication amongst Gram-positive bacteria (Dunny and Leonard 1997). Organized responses in a microbial colony were officially reported in the luminous marine bacterium. Aliivibrio fischeri in its symbiotic relationship with the Hawaiian squid, Euprymna scolopes. Bioluminescence was triggered and controlled by one or more signalling molecules accumulating in the extracellular environment of A. fischeri as their cell density increased and reached a critical number (quorum).

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