Base and acid resistance of B. subtilis associated with transcriptomic responses

Gene expression profiles of Bacillus subtilis strain AG174 were compared as a function of steady-state external pH during growth with aeration. Aerated overnight cultures were diluted 1:500 and incubated in 250 mL baffled flasks containing potassium-modified Luria-Bertani medium (LBK) buffered with 50 mM HOMOPIPES at pH 6.0, pH 7.0, and pH 9.0. Tubes were incubated at 37°C with aeration (260 rpm) to an optical density at 600 nm of 0.2. For each of the three pH conditions, RNA was isolated from five independent cultures. Overnight cultures were diluted 1:500 and incubated in 250 mL baffled flasks containing potassium-modified Luria-Bertani medium (LBK) buffered with 50 mM HOMOPIPES at pH 6.0, pH 7.0, and pH 9.0. Cultures were incubated at 37°C with aeration (260 rpm) to an optical density at 600 nm of 0.2. Five replicate cultures were grown at each pH.