Cells were obtained from cultures started in 25 mL sterile serum vials, in the same media at pH 7.6. Sealed serum vials were incubated at 37 °C with shaking at 240 rpm for 48 h. The OD 600 of the cultures was measured to determine the volume to add to each well, so that the initial OD 600 would be around 0.05 in each well. Once inoculated