A novelStaphylococcus aureus cis–transtype I toxin–antitoxin module with dual effects on bacteria and host cells

Abstract

Bacterial type I toxin–antitoxin (TA) systems are widespread, and consist of a stable toxic peptide whose expression is monitored by a labile RNA antitoxin. We characterized Staphylococcus aureus SprA2/SprA2 AS module, which shares nucleotide similarities with the SprA1/SprA1 AS TA system. We demonstrated that SprA2/SprA2 AS encodes a functional type I TA system, with the cis -encoded SprA2 AS antitoxin acting in trans to prevent ribosomal loading onto SprA2 RNA. We proved that both TA systems are distinct, with no cross-regulation between the antitoxins in vitro or in vivo . SprA2 expresses PepA2, a toxic peptide which internally triggers bacterial death. Conversely, although PepA2 does not affect bacteria when it is present in the extracellular medium, it is highly toxic to other host cells such as polymorphonuclear neutrophils and erythrocytes. Finally, we showed that SprA2 AS expression is lowered during osmotic shock and stringent response, which indicates that the system responds to specific triggers. Therefore, the SprA2/SprA2 AS module is not redundant with SprA1/SprA1 AS , and its PepA2 peptide exhibits an original dual mode of action against bacteria and host cells. This suggests an altruistic behavior for S. aureus in which clones producing PepA2 in vivo shall die as they induce cytotoxicity, thereby promoting the success of the community.

Analysis of the CodY RNome reveals RsaD as a stress‐responsive riboregulator of overflow metabolism in Staphylococcus aureus

“…RNAs were gel‐purified, eluted and precipitated with ethanol in the presence of 0.3 M sodium acetate. EMSAs and toeprint assays were performed as previously described (Germain‐Amiot et al, ) with some modifications. Native gel shift assays were conducted with 5 fmoles of purified labeled alsS .…”

“…Northern blots were performed as previously described (Germain-Amiot et al, 2019). Briefly, 10 μg of total RNAs was loaded and separated in 8% polyacrylamide/8M urea gels.…”

The Fst/Ldr Family of Type I TA System Toxins: Potential Roles in Stress Response, Metabolism and Pathogenesis

“…It was proposed that the cysteine residue might promote intermolecular disulfide bonds facilitating oligomerization and pore formation [19]. Curiously, PepA2, a S. aureus TA-1 toxin 50% identical to PepA1 and containing the same PXXXGC motif, does not lyse bacterial cells extracellularly but is approximately 10X more effective in lysing red blood cells [25]. Thus far, only PepA1 and LdrA have been experimentally determined to be located in the cytoplasmic membrane of their native hosts [19,21].…”

“…As with most TA toxins, the effects of Fst/Ldr superfamily toxins have been determined primarily in toxin over-producing strains. Thus far, overproduction of Fst pAD1 [1] and Fst EF0409 [27] of E. faecalis, PepA1 [19] and PepA2 [25] of S. aureus, fst-Sm of S. mutans [22], and LdrA [21] and LdrD [16] of E. coli have all been shown to cause cell death of their native hosts and, in the case of Fst pAD1 [15,28], PepA1 [24] and PepA2 [25], several heterologous hosts as well. In addition, the Lpt toxin from a par homolog on a L. rhamnosus plasmid was demonstrated to be toxic when over-produced in E. coli [26].…”

A peptide of a type I toxin-antitoxin system induces Helicobacter pylori morphological transformation from spiral-shape to coccoids

“…Toxins of type I TA systems from other organisms such as Escherichia coli, Bacillus subtilis or Staphylococcus aureus have been shown to localize to the inner membrane but there are no reports on induction of major cell shape modifications(4,21,32,33). The E.coli TisB(34) and the S. aureus PepA1 and PepA2(35,36) toxins act by creating membrane pores (similar to phage holins) thereby disrupting the membrane potential, drastically impairing ATP synthesis and depending on the toxin concentration, either leading to the formation of persisters or to cell death(9,33). One notable exception is the BsrG/SR4 Type I TA system of B. subtilis(32).…”