Small increases in sea expression were found in the transitional phase at pH 7.0 and

6.5. However, relative sea expression in the transitional phase at pH 6.0 (n = 2) and 5.5 (n = 3) were high, nine and four times higher, respectively, than in the exponential growth phase. At pH 5.5, extended sea mRNA expression was observed with the peak associated with the transitional phase. However, sea mRNA was not possible to detect selleck products at pH 5.0 or 4.5. Figure 1 Growth and relative sea levels of S. aureus Mu50 when grown at different pH levels. (A) Growth curves determined by OD measurements at 620 nm at pH 7.0, 6.5, 6.0, 5.5, 5.0, and 4.5. (B) Relative expression (RE) of sea at pH 7.0, 6.5, 6.0, and 5.5. Solid and dashed lines represent growth and RE, respectively. For pH 6.0 and 5.5, the mean and standard deviations of independent batch cultures; two and three, respectively, is displayed. Extracellular SEA was detected in all cultivations of S. aureus Mu50 and the levels increased over time at tested

pH levels allowing growth (Figure 2). The SEA levels increased from pH 7.0 to 6.0 and decreased significantly at lower pH levels, i.e. pH 5.5, 5.0 and 4.5. The specific extracellular SEA concentrations (i.e. the extracellular SEA concentrations divided by the value of the OD at that point in time) correlating the SEA production to growth, showed the same trend. The specific SEA concentrations were 100, 450, 510, 210, 40, and 870 ng per ml and OD unit for pH 7.0, 6.5, 6.0, 5.5, 5.0, and 4.5, respectively. The specific SEA concentration at pH 4.5 is misleading since the culture was not growing. Figure 2 SEA levels, growth rate and sea Ixazomib expression of S. aureus Mu50 at different pH levels. Extracellular others SEA levels in the mid-exponential, the transitional, the early stationary, and late stationary growth phase;

maximal growth rate (μmax), and relative sea levels (RE) in the transitional phase. At pH 4.5 the SEA values are after 10, 24 and 30 h of growth, shown in the figure as transitional, early stationary and late stationary phase samples, respectively. The values at pH 6.0 and 5.5 are the average and standard deviations of two and three independent batch cultures, respectively. Phage-associated sea expression Samples of bacterial cells and culture supernatants from S. aureus Mu50 were collected to determine the trends of the relative sea gene copy number (and thus the replicative form of the sea-carrying phage) and relative phage copy number in the four growth phases at different pH values (Figure 3). The relative sea gene copy number was low throughout the cultivations at pH 7.0 and 6.5. The sea gene copy number peaked at pH 5.5, being twelve times higher than at pH 7.0 in the mid-exponential growth phase, and a trend of the sea gene copy number decreasing over time was observed at this pH. The sea gene copy number increased over time at pH 5.0 and 4.