FIG. 3.

(A) Aerobic survival of E. coli QC2375 (sodA sodB recA) transformed with plasmids pUC18, pRS41.1, pJF119EH, and pRS51. Saturated anaerobic cultures were plated under anaerobic conditions (black) and aerobic conditions without (white) and with (shaded) 2 mM IPTG. CFU were counted after incubation overnight. Values are means of at least three independent experiments, and bars represent standard deviations. (B) Expression of S. meliloti sodA-lacZ in E. coli. Strain QC2461 was transformed with pRS58 and assayed for β-galactosidase activity in aerobiosis (circles) and anaerobiosis (squares).