RESUMO
Mycobacterium tuberculosis H37Ra (Mtb-Ra) ORF MRA_2875, annotated as malate:quinone oxidoreductase (mqo), is thought to have a role in TCA cycle in converting malate to oxaloacetate. To study its physiological relevance, we developed mqo knockout (KO) in Mtb-Ra. A KO complemented (KOC) strain was also developed by complementing the KO with mqo over-expressing construct. Under normal in vitro conditions, KO does not show any growth defect but showed reduced CFU burden in macrophages and in mice lungs. In vitro studies with KO showed reduced fitness under oxidative and low pH stress, and also increased susceptibility to levofloxacin and D-cycloserine. Transcript analysis of mqo showed increased expression levels under oxidative and low pH stress. This is the first study to show physiological relevance of mqo encoded by MRA_2875 in Mtb-Ra under oxidative and low pH stress. In summary, the present study shows that MRA_2875 encoded malate:quinone oxidoreductase is a functional enzyme which contributes to oxidative stress and low pH tolerance, and survival in macrophages and in mice.
