Sao Emani Carine, Reiling Norbert
Microbial Interface Biology, Research Center Borstel, Leibniz Lung Center, Borstel, Germany.
German Center for Infection Research (DZIF), Partner Site Hamburg-Lübeck-Borstel-Riems, Borstel, Germany.
Front Microbiol. 2024 Mar 4;15:1359188. doi: 10.3389/fmicb.2024.1359188. eCollection 2024.
It was previously shown that GlnA3 enabled to survive in excess polyamines. However, subsequent studies revealed that Rv1878, the corresponding (M.tb) ortholog, was not essential for the detoxification of spermine (Spm), in M.tb. On the other hand, the multi-drug efflux pump Rv1877 was previously shown to enable export of a wide range of compounds, while Rv0191 was shown to be more specific to chloramphenicol.
Therefore, we first wanted to determine if detoxification of Spm by efflux can be achieved by any efflux pump, or if that was dependent upon the function of the pump. Next, since Rv1878 was found not to be essential for the detoxification of Spm, we sought to follow-up on the investigation of the physiological role of Rv1878 along with Rv1877 and Rv0191.
To evaluate the specificity of efflux pumps in the mycobacterial tolerance to Spm, we generated unmarked ∆ and ∆ M.tb mutants and evaluated their susceptibility to Spm. To follow up on the investigation of any other physiological roles they may have, we characterized them along with the ∆ M.tb mutant.
The ∆ mutant was sensitive to Spm stress, while the ∆ mutant was not. On the other hand, the ∆ mutant grew better than the wild-type during iron starvation yet was sensitive to cell wall stress. The proteins Rv1877 and Rv1878 seemed to play physiological roles during hypoxia and acidic stress. Lastly, the ∆ mutant was the only mutant that was sensitive to oxidative stress.
The multidrug MFS-type efflux pump Rv1877 is required for Spm detoxification, as opposed to Rv0191 which seems to play a more specific role. Moreover, Rv1878 seems to play a role in the regulation of iron homeostasis and the reconstitution of the cell wall of M.tb. On the other hand, the sensitivity of the ∆ mutant to oxidative stress, suggests that Rv0191 may be responsible for the transport of low molecular weight thiols.
先前的研究表明，GlnA3能够在过量的多胺环境中存活。然而，随后的研究发现，结核分枝杆菌（M.tb）中对应的同源蛋白Rv1878对于精胺（Spm）的解毒并非必不可少。另一方面，先前的研究表明，多药外排泵Rv1877能够转运多种化合物，而Rv0191则对氯霉素具有更高的特异性。
因此，我们首先想确定Spm的外排解毒是否可以通过任何外排泵实现，或者这是否取决于泵的功能。接下来，由于发现Rv1878对于Spm的解毒并非必不可少，我们试图跟进对Rv1878与Rv1877和Rv0191生理作用的研究。
为了评估外排泵在分枝杆菌对Spm耐受性中的特异性，我们构建了无标记的结核分枝杆菌∆和∆突变体，并评估了它们对Spm的敏感性。为了跟进对它们可能具有的任何其他生理作用的研究，我们将它们与结核分枝杆菌∆突变体一起进行了表征。
∆突变体对Spm胁迫敏感，而∆突变体则不敏感。另一方面，∆突变体在铁饥饿期间比野生型生长得更好，但对细胞壁胁迫敏感。蛋白质Rv1877和Rv1878似乎在缺氧和酸性胁迫期间发挥生理作用。最后，∆突变体是唯一对氧化应激敏感的突变体。
多药MFS型外排泵Rv1877是Spm解毒所必需的，而Rv0191似乎发挥更具特异性的作用。此外，Rv1878似乎在结核分枝杆菌的铁稳态调节和细胞壁重建中发挥作用。另一方面，∆突变体对氧化应激的敏感性表明，Rv0191可能负责低分子量硫醇的转运。
