The small regulatory RNA molecule MicA is involved in Salmonella enterica serovar Typhimurium biofilm formation

Abstract

<p>Abstract</p> <p>Background</p> <p>LuxS is the synthase enzyme of the quorum sensing signal AI-2. In <it>Salmonella </it>Typhimurium, it was previously shown that a <it>luxS </it>deletion mutant is impaired in biofilm formation. However, this phenotype could not be complemented by extracellular addition of quorum sensing signal molecules.</p> <p>Results</p> <p>Analysis of additional <it>S. </it>Typhimurium <it>luxS </it>mutants indicated that the LuxS enzyme itself is not a prerequisite for a wild type mature biofilm. However, in close proximity of the <it>luxS </it>coding sequence, a small RNA molecule, MicA, is encoded on the opposite DNA strand. Interference with the MicA expression level showed that a balanced MicA level is essential for mature <it>Salmonella </it>biofilm formation. Several MicA targets known to date have previously been reported to be implicated in biofilm formation in <it>Salmonella </it>or in other bacterial species. Additionally, we showed by RT-qPCR analysis that MicA levels are indeed altered in some <it>luxS </it>mutants, corresponding to their biofilm formation phenotype.</p> <p>Conclusions</p> <p>We show that the <it>S. </it>Typhimurium biofilm formation phenotype of a <it>luxS </it>mutant in which the complete coding region is deleted, is dependent on the sRNA molecule MicA, encoded in the <it>luxS </it>adjacent genomic region, rather than on LuxS itself. Future studies are required to fully elucidate the role of MicA in <it>Salmonella </it>biofilm formation.</p