Upregulation of stress response genes and ABC transporters in anaerobic stationary-phase Mycobacterium smegmatis.

Oxygen starvation triggers an adaptive stationary-phase response in Mycobacterium smegmatis. During this anaerobic stationary phase, RNA synthesis continues at a low but significant level. Employing a modified expressed-sequence-tag (EST) approach, in combination with the M. tuberculosis genome data and comparative Northern analysis, we have identified the first genes that show an increase in transcription in M. smegmatis cells that have entered anaerobic stationary phase. One gene encodes the counterpart of the M. tuberculosis NifS-like protein Rv1464. Two genes are homologues of M. tuberculosis Rv1460 and Rv3368c, of unknown function. Strikingly, several genes induced by oxygen starvation encode putative stress protection proteins (counterparts of M. tuberculosis DnaK, Rv0350; betaine-aldehyde dehydrogenase, Rv0768; thioredoxin reductase, Rv3913) and ABC transporters (counterparts of M. tuberculosis Rv1463, Rv1473, Rv3197). We conclude that development of general stress resistance and certain active transport processes might play a role in the survival of oxygen-starved M. smegmatis.