# A Division-Associated Envelope Protein, MAB_2363, Drives Intrinsic Resistance and Virulence in Mycobacterium abscessus

## TL;DR

This study identifies MAB_2363 as a protein involved in cell division in Mycobacterium abscessus, which affects antibiotic resistance and virulence.

## Contribution

The study reveals MAB_2363 as a novel division-associated protein that influences intrinsic resistance and virulence in M. abscessus.

## Key findings

- Deletion of MAB_2363 increases antibiotic susceptibility and disrupts cell wall permeability.
- MAB_2363 is localized at division septa and is essential for normal cell division.
- MAB_2363 deletion leads to reduced virulence in macrophages and mouse models.

## Abstract

Mycobacterium abscessus exhibits intrinsic resistance to conventional antibiotics, significantly limiting treatment options. Our previous studies established that MAB_2362 (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 MAB_2363 encodes the corresponding SteB-like division regulator. In this study, we found that deletion of MAB_2363 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-MAB_2363 fusion protein demonstrated its enrichment at division septa, confirming its direct involvement in cell division. Furthermore, deletion of MAB_2363 led to attenuated virulence, as evidenced by reduced bacterial survival in macrophages and murine infection models. To assess its functional relation with MAB_2362, we compared the single-deletion mutant of MAB_2363 with the single-deletion mutant of MAB_2362 and the double-deletion mutant of MAB_2362-MAB_2363. Notably, the phenotypes of the MAB_2363 mutant, including cell division defects, antibiotic susceptibility, and virulence, were markedly milder than those of the other two mutants. Collectively, these findings indicate that MAB_2363 functions as a secondary but essential division-associated factor that operates during cell division, thereby influencing intrinsic resistance and virulence in M. abscessus.