Effect of aeration on the extreme acid survival of W3110, ΔhybC, ΔhycE, and ΔhypF.

The white bars represent cultures grown with aeration to stationary phase in LBK buffered at pH 5 that were diluted 200-fold into LBK pH 2 and exposed for 2 h with aeration at 37°C. The hatched and black bars represent anaerobic cultures grown to stationary phase in LBK buffered at pH 5.5 that were diluted 200-fold into LBK pH 2.5 (hatched) or pH 2 (black) and exposed for 2 h without aeration at 37°C. Aerobic and anaerobic cultures were maintained as stated in the Materials and Methods. Error bars represent SEM, n = 5 or 6.