Bacteria and growth conditions.Staphylococcus aureus D2H is a representative staphylococcus and was used for study. It was maintained on Trypticase soy agar slants (Difco) until experimentation. A slant culture initiated an overnight Trypticase soy broth culture that was used for the mid-exponential growth phase (optical density at 600 nm = 0.2) used for study. All liquid cultures were grown at 37°C, whereas the AFM liquid cell was held at 20°C in an attempt to slow growth for better surface visualization.