Growth, SEA levels, and sea mRNA levels of S. aureus SA45 grown at two pH levels. (A) Growth curves determined by OD measurements at 620 nm and extracellular SEA levels at pH 7.0 and pH 5.5. (B) Relative expression (RE) of sea at pH 7.0 and pH 5.5. Solid, dotted and dashed lines represents growth, SEA levels and RE, respectively. Values are the mean and standard deviations of two independent batch cultures.