FIG. 3.

Role of Mn-catalase during aerobic growth. (A) Identical amounts of anaerobically grown cells of T. thermophilus HB27::nar transformed with plasmid pMK18r (black circles) or pMK18cat (white circles) were inoculated in 12-ml tubes containing 3 ml of TB medium in the presence of the indicated concentrations of H₂O₂. The percentage of the OD₅₅₀ reached after 10 h of incubation at 70°C (microaerobic growth) with respect to untreated cultures compared to the H₂O₂ concentration is shown. (B) RT-PCR to detect the cat gene on total RNA from exponential cultures of T. thermophilus HB8 grown aerobically or after 7 h of anaerobic growth by nitrate respiration (anaerobic). The amounts of total RNA used were 4 μg (lane 1), 2 μg (lane 2), and 1 μg (lane 3). Lane M, size markers in kilobase pairs.