Exploring the physiological role and mode of action of the small RNA LhrC of Listeria monocytogenes and a recently discovered sigmaB-regulated sRNA of Staphylococcus aureus to check for their possible involvement in pathogenicity

• Applicant: Dr. Susanne Sievers
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2010 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 190827365

Small RNAs (sRNAs) play an important role in all kingdoms of life. They often act by pairing with specific target mRNAs to change their translation and/or stability or act to influence the activity of proteins. Small RNAs are also part of regulatory networks of the two human pathogens Listeria monocytogenes and Staphylococcus aureus and therefore most likely involved in virulence mechanisms. Numerous sRNAs have been discovered recently. Whereas in Gram-negative bacteria, foremost in Escherichia coli, a functional role has been assigned to many sRNAs, the state of knowledge concerning Gram-positive bacteria is lagging behind. In this context, the sRNA LhrC which is present in five almost identical copies in L. monocytogenes still requires functional classification. Interestingly, LhrC sRNAs have been shown to be up-regulated in blood and during the presence of beta-lactam antibiotics pointing to an involvement in virulence mechanisms. In the intended research project LhrC function will be explored primarily on proteome level by comparison of wild type and a mutant deleted in all five copies of LhrC in a comprehensive quantitative approach. More precisely the proteomics analysis will involve a metabolic labeling procedure based on 14N/15N isotopically labeled proteins, and will comprise not only the cytosolic proteome but also the membrane and extracellular protein fraction. Thereby identified putative LhrC targets will be backed up and complemented applying further strategies based on bioinformatics and biochemical fishing. In a second part of the project another sRNA of completely unknown function will be investigated employing a comparable experimental approach. This sRNA of S. aureus was shown to be sigmaB-regulated indicating a possible role during infection. The proposed research will contribute to the understanding of sRNA action in pathogenic Gram-positive bacteria and may provide a basis for new antimicrobial strategies.

• DFG Programme: Research Fellowships
• International Connection: Denmark
• Host: Professorin Dr. Birgitte H. Kallipolitis