Bacillus subtilis Regulators MntR and Zur Participate in Redox Cycling, Antibiotic Sensitivity, and Cell Wall Plasticity

Abstract

The <i>Bacillus subtilis</i> MntR and Zur transcriptional regulators control homeostasis of manganese and zinc, two essential elements required in various cellular processes. In this work, we describe the global impact of <i>mntR</i> and <i>zur</i> deletions at the protein level. Using a comprehensive proteomic approach, we showed that 33 and 55 proteins are differentially abundant in Δ<i>mntR</i> and Δ<i>zur</i> cells, respectively, including proteins involved in metal acquisition, translation, central metabolism, and cell wall homeostasis. In addition, both mutants showed modifications in intracellular metal ion pools, with significant Mg²⁺ accumulation in the Δ<i>mntR</i> mutant. Phenotypic and morphological analyses of Δ<i>mntR</i> and Δ<i>zur</i> mutants revealed their high sensitivity to lysozyme, beta-lactam antibiotics, and external oxidative stress. Mutant strains had a modified cell wall thickness and accumulated lower levels of intracellular reactive oxygen species (ROS) than the wild-type strain. Remarkably, our results highlight an intimate connection between MntR, Zur, antibiotic sensitivity, and cell wall structure.<b>IMPORTANCE</b> Manganese and zinc are essential transition metals involved in many fundamental cellular processes, including protection against external oxidative stress. In <i>Bacillus subtilis</i>, Zur and MntR are key transcriptional regulators of zinc and manganese homeostasis, respectively. In this work, proteome analysis of <i>B. subtilis</i> wild-type, Δ<i>mntR</i>, and Δ<i>zur</i> strains provided new insights into bacterial adaptation to deregulation of essential metal ions. Deletions of <i>mntR</i> and <i>zur</i> genes increased bacterial sensitivity to lysozyme, beta-lactam antibiotics, and external oxidative stress and impacted the cell wall thickness. Overall, these findings highlight that Zur and MntR regulatory networks are connected to antibiotic sensitivity and cell wall plasticity.