Up-regulation of narX, encoding a putative 'fused nitrate reductase' in anaerobic dormant Mycobacterium bovis BCG

Mycobacterium tuberculosis and its closely related but non-pathogenic relat ive M. bovis Bacille Calmette-Guerin (BCG) have the capability to adapt to anaerobiosis by shifting down from aerobic growth to a stale of non-replica ting persistence or dormancy. Here, we report the results of a comparative Northern analysis of 23 genes identified in the tubercle bacillus genome pr oject that might play a role in the energy metabolism under anaerobic condi tions. The expression of a majority of the genes was found to be down-regul ated in the dormant BCG Culture. However, the mRNA level for narX, a putati ve 'fused nitrate reductase' not found in other bacteria, was strongly up-r egulated in anaerobic dormant bacilli. narX is the first transcriptionally induced gene in anaerobic dormant mycobacteria and might be a useful marker for monitoring the dormancy response in infected animals. (C) 1999 Publish ed by Elsevier Science B.V. All rights reserved.