The ζ Toxin Induces a Set of Protective Responses and Dormancy

Abstract

The ζε module consists of a labile antitoxin protein, ε, which in dimer form (ε2) interferes with the action of the long-living monomeric ζ phosphotransferase toxin through protein complex formation. Toxin ζ, which inhibits cell wall biosynthesis and may be bactericide in nature, at or near physiological concentrations induces reversible cessation of Bacillus subtilis proliferation (protective dormancy) by targeting essential metabolic functions followed by propidium iodide (PI) staining in a fraction (20–30%) of the population and selects a subpopulation of cells that exhibit non-inheritable tolerance (1–5×10−5). Early after induction ζ toxin alters the expression of ∼78 genes, with the up-regulation of relA among them. RelA contributes to enforce toxin-induced dormancy. At later times, free active ζ decreases synthesis of macromolecules and releases intracellular K+. We propose that ζ toxin induces reversible protective dormancy and permeation to PI, and expression of ε2 antitoxin reverses these effects. At later times, toxin expression is followed by death of a small fraction (∼10%) of PI stained cells that exited earlier or did not enter into the dormant state. Recovery from stress leads to de novo synthesis of ε2 antitoxin, which blocks ATP binding by ζ toxin, thereby inhibiting its phosphotransferase activity.

Toxin ζ Reversible Induces Dormancy and Reduces the UDP-N-Acetylglucosamine Pool as One of the Protective Responses to Cope with Stress

“…Subsequent expression of the ε 2 antitoxin facilitates the exit from the dormant state and a fraction of membrane compromised cells recover their alteration of the membrane potential [14]. …”

“…Then, TLCs of the radiolabeled nucleotides or sugar nucleotides were performed on polyethyleneimine-cellulose plates with 0.85 M KH 2 PO 4 (pH 3.4) as the mobile phase as described [14] followed by autoradiography.…”

Toxin ζ Triggers a Survival Response to Cope with Stress and Persistence

“…BG1125 bearing lacI - P hsp wt ζ and pCB799-borne xylR - P xylA wt ε (Table 1), in which ζ gene expression (transcribed by P hsp ) is regulated by IPTG (Calbiochem, Spain) addition and the ε gene (transcribed by P xylA ) is regulated by xylose (Xyl, Sigma, USA) addition (Lioy et al, 2012), was grown in MMS7 supplemented with Xyl (0.05%). In the absence of IPTG [Sigma, USA] there are ~40 ζ toxin monomers/colony-forming units (CFU), which lead to genetic rearrangement.…”

“…Induction of genes involved in the SOS response was not observed, but the expression was documented of genes that could modulate toxin action, such as increased comGA and relA expression or decreased glmS gene expression (Lioy et al, 2012). It is likely that by altering ATP:GTP ratios, toxin ζY83C modifies availability of the initiating nucleotides; this in turn changes promoter preferences by RNA polymerase, and the intracellular signaling (Krasny and Gourse, 2004; Pedley and Benkovic, 2017).…”

The Presence of Conjugative Plasmid pLS20 Affects Global Transcription of Its Bacillus subtilis Host and Confers Beneficial Stress Resistance to Cells

“…Reverse transcription of RNA, cDNA labeling, and hybridization of the probes were performed as described before (17). From each time point at least three replicates of every comparison were hybridized to a B. subtilis microarray (18,19) and included in the analysis. Slides were scanned on a GMS 418 apparatus (Genetic Microsystems, Inc.).…”