The physiological effect of rimI/rimJ silencing by CRISPR interference in Mycobacterium smegmatis mc2155

N-terminal acetylation of proteins is an important post-translational modification (PTM) found in eukaryotes and prokaryotes. In bacteria, N-terminal acetylation is suggested to play various regulatory roles related to protein stability, gene expression, stress response, and virulence; however, the mechanism of such response remains unclear. The proteins, namely RimI/RimJ, are involved in N-terminal acetylation in mycobacteria. In this study, we used CRISPR interference (CRISPRi) to silence rimI/rimJ in Mycobacterium smegmatis mc(2)155 to investigate the physiological effects of N-terminal acetylation in cell survival and stress response. Repeat analysis of growth curves in rich media and biofilm analysis in minimal media of various mutant strains and wild-type bacteria did not show significant differences that could be attributed to the rimI/rimJ silencing. However, total proteome and acetylome profiles varied significantly across mutants and wild-type strains, highlighting the role of RimI/RimJ in modulating levels of proprotein acetylation in the cellular milieu. Further, we observed a significant increase in the minimum inhibitory concentration (MIC) (from 64 to 1024 mu g ml(-1)) for the drug isoniazid in rimI mutant strains. The increase in MIC value for the drug isoniazid in the mutant strains suggests the link between N-terminal acetylation and antibiotic resistance. The study highlights the utility of CRISPRi as a convenient tool to study the role of PTMs, such as acetylation in mycobacteria. It also identifies rimI/rimJ genes as necessary for managing cellular response against antibiotic stress. Further research would be required to decipher the potential of targeting acetylation to enhance the efficacy of existing antibiotics.