Plasmid-influenced changes in Mycobacterium avium catalase activity.

A virulent Mycobacterium avium strain, LR25, which carries three plasmids (18, 28, and 165 kilobases) and grows at 43 degrees C was compared with its plasmid-free, avirulent segregant, strain LR163, to identify the basis for the latter's inability to grow at 43 degrees C. The failure of mid-log-phase cultures of strain LR163 to grow at 43 degrees C was dependent on the presence of high levels of culture aeration. In addition, highly aerated cultures of strain LR163 failed to grow at 37 degrees C. Mid-log-phase cultures of strain LR163 had 30% of the catalase activity of strain LR25 and were more hydrogen peroxide (0.08%, wt/vol) susceptible. Catalase activity of strain LR25 was higher in cultures grown with high aeration than in those grown with almost no aeration. These data support the contention that plasmid-encoded genes influence M. avium catalase activity.