Figure 2.
Changes in glucose concentration and pH in the bulk media correspond to transitions between growth phases in S. aureus cultures. (A) Growth curves for S. aureus 6538 and S. aureus 10943 planktonic and biofilm cultures were plotted for all growth time periods. Cultures were inoculated with an equal amount of cell mass, as determined by comparable absorbance readings of seed flasks (i.e., OD600 nm). Time zero refers to mature biofilms grown up to 72 h (T0) and inoculum for planktonic cultures, respectively. Error bars have been calculated from growth curve measurements of duplicate biological replicates for each growth condition and growth time point. (B) Decreasing glucose concentration in the media for planktonic cultures corresponds in time to transition from exponential to stationary phase of growth. For biofilm cultures, consumption of glucose is below the detection limit of 1H 1D NMR for all time points of growth. (C) Changes in pH profile for planktonic cultures correspond in time to changes in growth rate, with significant pH differences between strains observed for biofilm cultures. Slight differences in bulk pH were detected between the two strains based on growth phase and growth phenotype.