FIG. 4.

Real-time PCR expression ratios of selected genes as a function of external pH. B. subtilis strain AG174 overnight cultures in unbuffered LBK were diluted 500-fold into LBK buffered with 50 mM HOMOPIPES at pH 6.0, at pH 7.0, and at pH 9.0. RNA was isolated, and mRNA expression for individual genes was quantified by real-time PCR using an ABI Prism 7500 DNA analyzer (Applied Biosystems) with SYBR Green one-step protocol. All expression levels are presented relative to the expression at pH 7.0. Error bars represent the SEM (n = 3).