Construction of S. aureus Gene Knockout Strains

S. aureus USA500 (Diep et al., 2006 (link)) was used for construction of gene knockout and complementation strains. E. coli DC10B (Monk et al., 2012 (link)) was used for shuttle plasmid construction. Luria Broth medium was composed of 1% tryptone (Oxoid), 0.5% yeast extract (Oxoid) and 0.5% NaCl; BM (B-Medium) was composed of 1% tryptone, 0.5% yeast extract, 0.5% glucose, 0.1% K₂HPO₄ and 0.5% NaCl; BM and TSB (Tryptic soy broth, Oxoid) were used for S. aureus cultivation. Bacterial strains were inoculated in BM, and their growth rate at 37°C was monitored by measuring the OD values at 600 nm. Anhydrotetracycline (ATc) was used for induction of secY antisense RNA during gene knockout. Antibiotics were added to medium at the following concentrations: chloramphenicol, 10 μg/ml; ampicillin, 100 μg/ml, levofloxacin, 50 μg/ml.