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

Abstract

The Bacillus subtilis 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 mntR and zur deletions at the protein level. Using a comprehensive proteomic approach, we showed that 33 and 55 proteins are differentially abundant in ΔmntR and Δzur 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 ΔmntR mutant. Phenotypic and morphological analyses of ΔmntR and Δzur 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. IMPORTANCE Manganese and zinc are essential transition metals involved in many fundamental cellular processes, including protection against external oxidative stress. In Bacillus subtilis, Zur and MntR are key transcriptional regulators of zinc and manganese homeostasis, respectively. In this work, proteome analysis of B. subtilis wild-type, ΔmntR, and Δzur strains provided new insights into bacterial adaptation to deregulation of essential metal ions. Deletions of mntR and zur 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.

Antimicrobial nanoparticles and biodegradable polymer composites for active food packaging applications

“…ZnO NPs may also release cytotoxic Zn 2+ ‐ions upon their partial dissolving (Vidic et al., 2014). Namely, ZnO NPs can release Zn 2+ ‐ions intracellularly that disturb bacterial redox potential (Randazzo et al., 2020). Seray et al.…”

Iron homeostasis in Bacillus subtilis relies on three differentially expressed efflux systems

“…In contrast with pfeT mutants, it has been reported that mntR mutants are more H 2 O 2 -sensitive than WT in LB medium [15, 49]. However, this phenotype is very sensitive to the precise metal content of the medium.…”

Synthesis and antibacterial activity of iron manganite (FeMnO3) particles against the environmental bacteriumBacillus subtilis

“…However, high concentrations of Mn ions (of about 66.42 mM) observed in LB medium will hardly be tolerated by bacterial cells, because intracellular metal homeostasis in bacteria is ensured by nely tuned import and efflux systems. 45 It seems that both hydrogen ion generation and Mn-ion release of FeMnO 3 particles induce strong DPPH radical scavenging indicating an antioxidant effect.…”

“…Previous studies have shown that bacterial cells may neutralize H 2 O 2 by catalyse or some superoxide enzymes, and in such way cope with acute oxidative stress. 7,45 We next sought to evaluate for any potential cytotoxicity of FeMnO 3 dissolved in bacterial media. The impact of different concentrations of FeMnO 3 was studied by measuring grown kinetics of a B. subtilis hospital isolate (NDMed).…”

“…B. subtilis possesses complex regulatory mechanisms to maintain intracellular Fe-and Mn-ions homeostasis for environmental concentrations, but cannot tolerate concentrations similar to those quantied here for FeMnO 3 in LB solution by the ICP-OES analysis. 45,47,48 Other mechanisms of antibacterial activity of metal oxide particles have been proposed recently. 'Omics' data have indicated that ZnO nanoparticles trigger enzyme inhibition and perturbation in carbohydrate metabolism and bioenergetics in Staphylococcus aureus by a ROS independent mechanism.…”