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Bacteriocins are proteinaceous antimicrobials produced by bacteria, which are active against other strains of the same species. R-type pyocins are phage tail-like bacteriocins produced by Pseudomonas aeruginosa, a Gram-negative opportunistic pathogen known to be problematic in chronic infections. Due to their anti-pseudomonal activity, R-pyocins have potential as therapeutics in infection. However little is understood regarding the effects of cell lysis in infection, nor the specific timing of R-pyocin induction and release. Similar to prophages, R-pyocins are located on the chromosome and are induced by the SOS response via DNA-damaging agents. Following SOS activation, R-pyocins are produced and then released into the environment by lysis of the producing cells. While several DNA-damaging agents are known to induce R-pyocin activity – including mitomycin C, ciprofloxacin, and hydrogen peroxide – it is unknown if all agents induce R-pyocin production to the same magnitude or along the same temporal regime. The induction of R-pyocins by the SOS response in P. aeruginosa also suggests that there may be regulatory ties between pyocins and chromosomal prophages - also induced under the same response. However, the regulation of R-pyocins and prophage have yet to be disentangled. There are two more lytic systems in P. aeruginosa that may also play a role in R-pyocin release: the Alp and the Cid systems, which have previously been ignored in much of the R-pyocin work thus far.
Using chromosomal transcriptional reporters, we have generated a number of strains to (i) quantify the regulatory activity of various R-pyocin genes, (ii) assess gene expression by disparate induction agents, (iii) establish a timeline of R-pyocin regulation, from induction to lysis, and (vi) disentangle the involvement of prophage and other lytic systems in the regulation of pyocins in P. aeruginosa. Overall, our work provides a more cohesive picture of R-pyocin regulation in P. aeruginosa.