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

Abstract

Bacteria have evolved complex regulatory controls in response to various environmental stresses. Protein toxins of the ζ superfamily, found in prominent human pathogens, are broadly distributed in nature. We show that ζ is a uridine diphosphate-N-acetylglucosamine (UNAG)-dependent ATPase whose activity is inhibited in vitro by stoichiometric concentrations of ε2 antitoxin. In vivo, transient ζ expression promotes a reversible multi-level response by altering the pool of signaling purine nucleotides, which leads to growth arrest (dormancy), although a small cell subpopulation persists rather than tolerating toxin action. High c-di-AMP levels (absence of phosphodiesterase GdpP) decrease, and low c-di-AMP levels (absence of diadenylate cyclase DisA) increase the rate of ζ persistence. The absence of CodY, a transition regulator from exponential to stationary phase, sensitizes cells to toxin action, and suppresses persisters formed in the ΔdisA context. These changes, which do not affect the levels of stochastic ampicillin (Amp) persistence, sensitize cells to toxin and Amp action. Our findings provide an explanation for the connection between ζ-mediated growth arrest (with alterations in the GTP and c-di-AMP pools) and persistence formation.

Identification and functional characterization of a bacterial homologue of Zeta toxin in Leishmania donovani

“…The second hypothesis might be that when the parasites switch from vector to host or vice versa, it encounters stressed condition that leads to death of certain parasites that might be regulated by the expression of Ld_f1. This death might provide the nutrients to the persister parasites, which is in good accordance to the phenomenon reported in bacteria where activation of zeta under stress condition is linked to persistence formation, allowing the bacteria to survive under nutrient deficient conditions [31].…”

“…A prominent association curve was observed at and beyond 1.5 mM ATP concentrations (Fig. This death might provide the nutrients to the persister parasites, which is in good accordance to the phenomenon reported in bacteria where activation of zeta under stress condition is linked to persistence formation, allowing the bacteria to survive under nutrient deficient conditions [31]. Based on these findings, we conclude that the zeta domain of Ld_f1 not only phosphorylates its substrate UNAG but also exhibits autophosphorylation property by hydrolyzing ATP.…”

Towards Exploring Toxin-Antitoxin Systems in <em>Geobacillus</em>: A Screen for Type II Toxin-Antitoxin System Families in A Thermophilic Genus

“…The principle of delaying cell death has also been reported in the same study [107]. Additionally, the existence of an interconnection between a type II toxin and second messengers, the (p)ppGpp and the c-di-AMP has been reported previously in [122]. Álamo and coworkers have reported an interrelationship between a type II toxin (ξ), the (p)ppGpp, the c-di-AMP, and other nucleotides [122].…”

“…Additionally, the existence of an interconnection between a type II toxin and second messengers, the (p)ppGpp and the c-di-AMP has been reported previously in [122]. Álamo and coworkers have reported an interrelationship between a type II toxin (ξ), the (p)ppGpp, the c-di-AMP, and other nucleotides [122]. However, the effects of these two messengers on inducing the TA expression were not studied since the expression was controlled by external inducers [122].…”

“…Since (p)ppGpp is synthesized from GTP/GDP and since the high level of (p)ppGpp inhibits salvaging and de novo synthesis of these nucleotides [115,116,120,121], the synthesis of further (p)ppGpp will cease. The same applies to c-di-AMP since metabolically inactive cells have a reduced proton motive force (PMF) (i.e., reduced ATP level) [122,123]. The cessation of further formation of the two messengers could protect the cell from "early" death, with the hope that the conditions may improve.…”