Global Insights\ninto the Lysine Acetylome Reveal the\nRole of Lysine Acetylation in the Adaptation of <i>Bacillus altitudinis</i> to Salt Stress

<i>Bacillus altitudinis</i> is a well-known\nbeneficial\nmicroorganism in plant rhizosphere, capable of enhancing plant growth\nand salt tolerance in saline soils. However, the mechanistic changes\nunderlying salt tolerance in <i>B. altitudinis</i> at the\nlevel of post-translational modifications remain unclear. Here, diverse\nlysine modifications including acetylation, succinylation, crotonylation,\nand malonylation were determined in the <i>B. altitudinis</i> response to salt stress by immunodetection, and the acetylation\nlevel greatly increased under salt stress. The in-depth acetylome\nlandscape showed that 1032 proteins in <i>B. altitudinis</i> were differentially acetylated under salt stress. These proteins\nwere involved in many physiological aspects closely related to salt\ntolerance like energy generation and conversion, amino acid synthesis\nand transport, cell motility, signal transduction, secretion system,\nand repair system. Moreover, we also identified the differential acetylation\nof key enzymes involved in the major osmolyte biosynthesis and conversion\nand antioxidant defenses. Thiol peroxidase (TPX), a key protective\nantioxidant enzyme, had 3 upregulated acetylation sites (K7/139/157)\nunder salt stress. Site-specific mutations demonstrated that K7/139/157\nacetylation strongly regulated TPX function in scavenging intracellular\nROS, thereby impacting bacterial growth under salt stress. To our\nknowledge, this is the first study showing that bacteria adaptation\nto salt stress occurs at the level of PTMs.