The impact of genotype on the phenotype of Mycobacterium tuberculosis AsufR mutants

Iron-sulphur (FeS) cluster biogenesis is a tightly regulated process in vivo. In Mycobacterium tuberculosis (Mtb), SufR functions as a transcriptional repressor of the operon encoding the primary FeS cluster biogenesis system. Previously, three independently isolated mutants (ARv1460stop_1.19, ARv1460stop _5.19 and ARv1460stop _5.20) harbouring the same deletion in sufR, displayed different growth kinetics in OADC supplemented 7H9 media. To investigate this discrepancy, we performed whole genome sequencing of the 3 mutants and the wildtype progenitor. Single nucleotide polymorphisms (SNPs) were identified in 3 genes in the dRv1460stop_1.19 mutant and one gene in the dRv1460stop_5.20 mutant. Phenotyping of the dRv1460stop_5.19 mutant, which had no additional SNPs, revealed increased susceptibility to clofazimine, DMNQ and menadione, while uptake and survival in THP-1 cells were not significantly different from the wild-type strain. Given that these results differ from those reported for other sufR deletion mutants (dSufRMTB and MtbdSufR), they suggest that the position of the sufR deletion and the genotype of the progenitor strain impact the resulting phenotype.