Key Laboratory of Special Pathogens and Biosafety, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan, 430071, People's Republic of China.
University of Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
Sci Rep. 2021 Jan 14;11(1):1352. doi: 10.1038/s41598-020-80213-4.
Previous studies showed that mutation of folC caused decreased expression of the dihydropteroate synthase encoding gene folP2 in Mycobacterium tuberculosis (M. tuberculosis). We speculated that mutation of folC in M. tuberculosis might affect the susceptibility to sulfamethoxazole (SMX). To prove this, 53 clinical isolates with folC mutations were selected and two folC mutants (I43A, I43T) were constructed based on M. tuberculosis H37Ra. The results showed that 42 of the 53 clinical isolates (79.2%) and the two lab-constructed folC mutants were more sensitive to SMX. To probe the mechanism by which folC mutations make M. tuberculosis more sensitive to SMX, folP2 was deleted in H37Ra, and expression levels of folP2 were compared between H37Ra and the two folC mutants. Although deletion of folP2 resulted in increased susceptibility to SMX, no difference in folP2 expression was observed. Furthermore, production levels of para-aminobenzoic acid (pABA) were compared between the folC mutants and the wild-type strain, and results showed that folC mutation resulted in decreased production of pABA. Taken together, we show that folC mutation leads to decreased production of pABA in M. tuberculosis and thus affects its susceptibility to SMX, which broadens our understanding of mechanisms of susceptibilities to antifolates in this bacterium.
先前的研究表明，folC 突变导致结核分枝杆菌（M. tuberculosis）中二氢喋啶合酶编码基因 folP2 的表达降低。我们推测，结核分枝杆菌中 folC 的突变可能会影响磺胺甲恶唑（SMX）的敏感性。为了证明这一点，我们选择了 53 株具有 folC 突变的临床分离株，并基于 M. tuberculosis H37Ra 构建了两个 folC 突变体（I43A、I43T）。结果表明，53 株临床分离株中有 42 株（79.2%）和两个实验室构建的 folC 突变体对 SMX 更敏感。为了探究 folC 突变使结核分枝杆菌对 SMX 更敏感的机制，我们在 H37Ra 中缺失了 folP2，并比较了 H37Ra 和两个 folC 突变体之间 folP2 的表达水平。尽管缺失 folP2 导致对 SMX 的敏感性增加，但 folP2 的表达水平没有差异。此外，我们比较了 folC 突变体和野生型菌株之间对 para-aminobenzoic acid (pABA) 的产生水平，结果表明 folC 突变导致 pABA 的产生减少。总之，我们表明 folC 突变导致结核分枝杆菌中 pABA 的产生减少，从而影响其对 SMX 的敏感性，这拓宽了我们对该细菌中抗叶酸药物敏感性机制的理解。
