The small regulatory RNA molecule MicA is involved in Salmonella enterica serovar Typhimurium biofilm formation.
BACKGROUND
LuxS is the synthase enzyme of the quorum sensing signal AI-2. In Salmonella Typhimurium, it was previously shown that a luxS deletion mutant is impaired in biofilm formation. However, this phenotype could not be complemented by extracellular addition of quorum sensing signal molecules.


RESULTS
Analysis of additional S. Typhimurium luxS mutants indicated that the LuxS enzyme itself is not a prerequisite for a wild type mature biofilm. However, in close proximity of the luxS 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 Salmonella biofilm formation. Several MicA targets known to date have previously been reported to be implicated in biofilm formation in Salmonella or in other bacterial species. Additionally, we showed by RT-qPCR analysis that MicA levels are indeed altered in some luxS mutants, corresponding to their biofilm formation phenotype.


CONCLUSIONS
We show that the S. Typhimurium biofilm formation phenotype of a luxS mutant in which the complete coding region is deleted, is dependent on the sRNA molecule MicA, encoded in the luxS adjacent genomic region, rather than on LuxS itself. Future studies are required to fully elucidate the role of MicA in Salmonella biofilm formation.
Centre of Microbial and Plant Genetics, KU Leuven, Kasteelpark Arenberg 20, 3001 Leuven, Belgium.
Gwendoline
G
Kint
David
D
De Coster
Kathleen
K
Marchal
Jos
J
Vanderleyden
Sigrid C J
SC
De Keersmaecker
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018441:Biofilms; D013437:Carbon-Sulfur Lyases / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism*; D058727:RNA, Small Untranslated / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics / Q000502:physiology*
D001426:Bacterial Proteins; D012329:RNA, Bacterial; D058727:RNA, Small Untranslated; D013437:Carbon-Sulfur Lyases; C117753:LuxS protein, Bacteria