Comparative transcriptome analysis of two S. aureus strains with different susceptibilities to mersacidin.

The lantibiotic mersacidin is an antimicrobial peptide of 20 amino acids that is produced by Bacillus sp. strain HIL Y-85,54728. Lantibiotics are antibiotics containing nonproteinogenic amino acids like lanthionine and/or 3-methyllanthionine. Mersacidin interferes with cell wall biosynthesis by targeting the peptidoglycan precursor lipid II and inhibits the growth of MRSA and other gram-positive bacteria. Therefore, mersacidin could be a lead substance for the development of new antibacterial agents. The clinical VISA isolates S. aureus 137/93A and its spontaneous mutant S. aureus 137/93G show reduced sensitivity towards mersacidin. This phenotype could not be traced to factors being responsible for vancomycinresistance (i.e. the thickened cell wall). Here, we focussed on the comparative transcriptome analysis of S. aureus 137/93A and S. aureus SG511 (sensitive strain) via full genome S. aureus microarrays to identify genes involved in the reduced sensitivity towards mersacidin. In this experiment, the transcriptomes of S. aureus 137/93A and S. aureus SG511 (sensitive strain) should be compared via microarray analysis. To this end, S. aureus 137/93A and S. aureus SG511 were grown without mersacidin to determine the genes which are differently expressed in these strains. Each experiment was performed 2 times including a dye swap resulting in two chips per competitive comparison with the incorporated dye reversed. All hybridizations were done with equal amounts of fluorescence-labeled cDNA probes or picomols of dye.