Ribosome stalling during translation significantly reduces cell viability, because cells have to spend resources on the synthesis of new ribosomes. Therefore, all bacteria have developed various mechanisms of ribosome rescue. Usually, the release of ribosomes is preceded by hydrolysis of the tRNApeptide bond, but, in some cases, the ribosome can continue translation thanks to the activity of certain factors. This review describes the mechanisms of ribosome rescue thanks to trans-translation and the activity of the ArfA, ArfB, BrfA, ArfT, HflX, and RqcP/H factors, as well as continuation of translation via the action of EF-P, EF-4, and EttA. Despite the ability of some systems to duplicate each other, most of them have their unique functional role, related to the quality control of bacterial translation in certain abnormalities caused by mutations, stress cultivation conditions, or antibiotics.

In the bid to survive and thrive in an environmental setting, bacterial species constantly interact and compete for resources and space in the microbial ecosystem. Thus, they have adapted to use various antibiotics and toxins to fight their rivals. Simultaneously, they have evolved an ability to withstand weapons that are directed against them. Several bacteria harbor colicinogenic plasmids which encode toxins that impair the translational apparatus. One of them, colicin E3 ribotoxin, mediates cleavage of the 16S rRNA in the decoding center of the ribosome. In order to thrive upon deployment of such ribotoxins, competing bacteria may have evolved counter-conflict mechanisms to prevent their demise. A recent study demonstrated the role of PrfH and the RtcB2 module in rescuing a damaged ribosome and the subsequent re-ligation of the cleaved 16S rRNA by colicin E3 in vitro. The rtcB2-prfH genes coexist as gene neighbors in an operon that is sporadically spread among different bacteria. In the current study, we report that the RtcB2-PrfH module confers resistance to colicin E3 toxicity in E. coli ATCC25922 cells in vivo. We demonstrated that the viability of E. coli ATCC25922 strain that is devoid of rtcB2 and prfH genes is impaired upon action of colicin E3, in contrast to the parental strain which has intact rtcB2 and prfH genes. Complementation of the rtcB2 and prfH gene knockout with a high copy number-plasmid (encoding either rtcB2 alone or both rtcB2-prfH operon) restored resistance to colicin E3. These results highlight a counter-conflict system that may have evolved to thwart colicin E3 activity.