Mutants of Mycobacterium tuberculosis Lacking Three of the Five rpf-Like Genes Are Defective for Growth In Vivo and for Resuscitation In Vitro

• Published in: Infection and Immunity 2005-05, Vol.73 (5), p.3038-3043
• Main Authors: Downing, Katrina J, Mischenko, Vladimir V, Shleeva, Margarita O, Young, Danielle I, Young, Michael, Kaprelyants, Arseny S, Apt, Alexander S, Mizrahi, Valerie
• Format: Article
• Language: English
• Subjects: Animals; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Culture Media; Cytokines - genetics; Cytokines - metabolism; Gene Deletion; Gene Expression Regulation, Bacterial; Genes, Bacterial; Humans; Mice; Mice, Inbred C57BL; Micrococcus luteus; Molecular Pathogenesis; Multigene Family; Mutation; Mycobacterium tuberculosis; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - growth & development; Mycobacterium tuberculosis - pathogenicity; Tuberculosis, Pulmonary - microbiology; Virulence
• ISSN: 0019-9567; 1098-5522
• DOI: 10.1128/IAI.73.5.3038-3043.2005

Mycobacterium tuberculosis contains five genes, rpfA through rpfE, that bear significant homology to the resuscitation-promoting factor (rpf) gene of Micrococcus luteus, whose product is required to resuscitate the growth of dormant cultures of M. luteus and is essential for the growth of this organism. Previous studies have shown that deletion of any one of the five rpf-like genes did not affect the growth or survival of M. tuberculosis in vitro. In conjunction with the results of whole-genome expression profiling, this finding was indicative of their functional redundancy. In this study, we demonstrate that the single deletion mutants are phenotypically similar to wild-type M. tuberculosis H37Rv in vivo. The deletion of individual rpf-like genes had no discernible effect on the growth or long-term survival of M. tuberculosis in liquid culture, and the ability to resuscitate spontaneously from a nonculturable state in a most probable number assay was also unaffected for the three strains tested (the [Delta]rpfB, [Delta]rpfD, and [Delta]rpfE strains). In contrast, two multiple strains, KDT8 ([Delta]rpfA-mutation [Delta]rpfC [Delta]rpfB) and KDT9 ([Delta]rpfA [Delta]rpfC [Delta]rpfD), which lack three of the five rpf-like genes, were significantly yet differentially attenuated in a mouse infection model. These mutants were also unable to resuscitate spontaneously in vitro, demonstrating the importance of the Rpf-like proteins of M. tuberculosis in resuscitation from the nonculturable state. These results strongly suggest that the biological functions of the five rpf-like genes of M. tuberculosis are not wholly redundant and underscore the potential utility of these proteins as targets for therapeutic intervention.