Mycobacterium tuberculosis H37Rv possesses five resuscitation-promoting factors, RpfA-E, which are required for the resuscitation of dormancy in mycobacteria induced by prolonged incubation of the culture in stationary phase. This study explores the transcriptional profile of all the rpf-like genes of M. tuberculosis H37Rv in the exponential phase, stationary phase, nonculturable phase and Rpf-mediated resuscitation phase. The relative expression was also monitored under acid stress, nutrient

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... arvation and low-oxygen (hypoxia) conditions by real-time quantitative PCR. We show differential relative expression of the rpf genes during different stages of growth and under stress. During early resuscitation, all rpf genes were expressed with maximal expression ratios for rpfA and rpfD. rpfC was consistently expressed during all stages of growth and nutrient starvation. Acid stress induced higher relative expression of rpfD and rpfE and hypoxia of rpfC and rpfE. These results therefore provide further evidence that the rpf genes perform distinct roles during cell growth and cell survival under different physiological stresses, and are consistent with the rpf-like genes being differentially regulated. Abbreviations: NC, non-culturable; NCC non-culturable cells. A set of supplementary methods, describing the protocol for cDNA synthesis, a supplementary figure, showing amplification efficiency for each primer set, and a supplementary table, showing the data used to calculate the normalized ratios, are available with the online version of this paper. Microbiology