Global expression profiling of strains harbouring null mutations reveals that the five rpf-like genes of Mycobacterium tuberculosis show functional redundancy.
METHODS
Aged, dormant cultures of Mycobacterium tuberculosis can be resuscitated by a secreted, proteinaceous growth factor from Micrococcus luteus, known as resuscitation-promoting factor (Rpf). M. tuberculosis contains five rpf-like genes, rpfA (Rv0867c), rpfB (Rv1009), rpfC (Rv1884c), rpfD (Rv2389c) and rpfE (Rv2450c), that bear significant similarity to Mi. luteus rpf, suggesting that these too may play a role in growth and/or reactivation from a quiescent state.


OBJECTIVE
Unmarked deletion mutants of each of the five rpf-like genes of M. tuberculosis H37Rv were constructed and their phenotypes and global gene expression profiles were assessed.


CONCLUSIONS
Deletion of any one of the rpf-like genes did not affect growth or survival of M. tuberculosis in liquid culture, but some alterations in colony-forming ability and colonial morphology were observed. Global gene expression profiling suggested that loss of rpfC affected the expression of the largest number of genes and there was a significant overlap in the differential gene expression profile of the rpfC mutant with those of the rpfB, rpfD and rpfE mutants. The expression profile of the rpfA mutant was notably less similar, but inverse associations with genes affected in the other mutants were observed. These results, together with those obtained by real-time, quantitative RT-PCR, suggest that the rpf-like genes serve wholly or partially overlapping functions in M. tuberculosis.
Downing
K J
KJ
MRC/NHLS/WITS Molecular Mycobacteriology Research Unit, School of Pathology of the University of the Witwatersrand and the National Health Laboratory Service, P.O. Box 1038, Johannesburg 2000, South Africa.
Betts
J C
JC
Young
D I
DI
McAdam
R A
RA
Kelly
F
F
Young
M
M
Mizrahi
V
V
D001426:Bacterial Proteins / Q000235:genetics*; D016000:Cluster Analysis; D015169:Colony Count, Microbial; D016207:Cytokines / Q000235:genetics*; D017353:Gene Deletion; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000235:genetics* / Q000254:growth & development; D020133:Reverse Transcriptase Polymerase Chain Reaction
D001426:Bacterial Proteins; D016207:Cytokines; C113704:resuscitation-promoting factor, bacteria