Northern blot analysis of RNAIII (2A) or spa mRNA (2B) expression in S. aureus WT and Δhfq strains. Total RNA was extracted from post-exponential phase cultures of RN6390, Newman and COL, WT and Δhfq strains. 15 μg of total RNA of RN6390 and Newman strains were analysed by northern blot, using an RNAIII-specific probe (2A). Total RNA from RN6390, Newman and COL strains was also compared for spa mRNA expression, using a spa-specific probe (2B). Results from three independent experiments were identical.