Mycobacterium abscessus exhibits intrinsic resistance to conventional antibiotics, significantly limiting treatment options. Our previous studies established that MAB₂362 (SteA) is a key regulator of cell division that contributes to intrinsic resistance and virulence. Considering that SteA-like proteins often act alongside SteB counterparts, we hypothesized that the adjacent gene MAB₂363 encodes the corresponding SteB-like division regulator. In this study, we found that deletion of MAB₂363 significantly increased susceptibility to multiple antibiotics and disrupted cell wall permeability. Microscopy revealed pronounced cell division defects in the mutant, including elongated cell morphology and multiple septa. Subcellular localization of a GFP-MAB₂363 fusion protein demonstrated its enrichment at division septa, confirming its direct involvement in cell division. Furthermore, deletion of MAB₂363 led to attenuated virulence, as evidenced by reduced bacterial survival in macrophages and murine infection models. To assess its functional relation with MAB₂362, we compared the single-deletion mutant of MAB₂363 with the single-deletion mutant of MAB₂362 and the double-deletion mutant of MAB₂362-MAB₂363. Notably, the phenotypes of the MAB₂363 mutant, including cell division defects, antibiotic susceptibility, and virulence, were markedly milder than those of the other two mutants. Collectively, these findings indicate that MAB₂363 functions as a secondary but essential division-associated factor that operates during cell division, thereby influencing intrinsic resistance and virulence in M. abscessus.
Li et al. (Mon,) studied this question.