Open AccessA single‐nucleotide mutation in the −10 promoter region inactivates the narK2X promoter in Mycobacterium bovis and Mycobacterium bovis BCG and has an application in diagnosis
Author(s) -
Chauhan Santosh,
Singh Alka,
Tyagi Jaya Sivaswami
Publication year - 2010
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2009.01876.x
Subject(s) - mycobacterium bovis , microbiology and biotechnology , mycobacterium , biology , mycobacterium tuberculosis , operon , nitrate reductase , promoter , gene , tuberculosis , bacteria , gene expression , escherichia coli , genetics , biochemistry , enzyme , medicine , pathology
Nitrate reduction is believed to be vital for the survival of tubercle bacteria under hypoxic/anaerobic conditions that are thought to prevail within granulomas. Nitrate reductase activity is rapidly induced in Mycobacterium tuberculosis ( M. tb ) under hypoxic conditions and is attributed to the induced expression of the nitrate/nitrite transporter gene, narK2 . By contrast, Mycobacterium bovis ( M. bovis ) and M. bovis BCG (BCG) do not support the hypoxic induction of either nitrate reductase activity or narK2 . Here, we show that the induction defect in the narK2X operon in M. bovis and BCG is caused by a −6T/C single nucleotide polymorphism (SNP) in the −10 promoter element essential for narK2X promoter activity. Complementation of M. bovis with both narGHJI and narK2X genes from M. tb failed to restore nitrate reductase activity in M. bovis , suggesting the involvement of additional genes/regulatory mechanisms for nitrate reduction that are absent in M. bovis . The −6T/C promoter‐linked SNP enabled clear differentiation of M. tb from the other members of the M. tb complex, including M. bovis , BCG, Mycobacterium africanum and Mycobacterium microti , through a PCR‐RFLP assay.