Biological Cost of Pyocin Production during the SOS Response in Pseudomonas aeruginosa

Abstract

bLexA and two structurally related regulators, PrtR and PA0906, coordinate the Pseudomonas aeruginosa SOS response. RecAmediated autocleavage of LexA induces the expression of a protective set of genes that increase DNA damage repair and tolerance. In contrast, RecA-mediated autocleavage of PrtR induces antimicrobial pyocin production and a program that lyses cells to release the newly synthesized pyocin. Recently, PrtR-regulated genes were shown to sensitize P. aeruginosa to quinolones, antibiotics that elicit a strong SOS response. Here, we investigated the mechanisms by which PrtR-regulated genes determine antimicrobial resistance and genotoxic stress survival. We found that induction of PrtR-regulated genes lowers resistance to clinically important antibiotics and impairs the survival of bacteria exposed to one of several genotoxic agents. Two distinct mechanisms mediated these effects. Cell lysis genes that are induced following PrtR autocleavage reduced resistance to bactericidal levels of ciprofloxacin, and production of extracellular R2 pyocin was lethal to cells that initially survived UV light treatment. Although typically resistant to R2 pyocin, P. aeruginosa becomes transiently sensitive to R2 pyocin following UV light treatment, likely because of the strong downregulation of lipopolysaccharide synthesis genes that are required for resistance to R2 pyocin. Our results demonstrate that pyocin production during the P. aeruginosa SOS response carries both expected and unexpected costs.

Competition in biofilms between cystic fibrosis isolates ofPseudomonas aeruginosais shaped by R-pyocins

“…With little genetic redundancy in the bacterial genome, the incorporation of an extra S pyocin gene will be more amenable to genetic restructuring than the assembly of multiple R-type operons. Indeed, many P. aeruginosa strains possess extra 'orphan' immunity genes to the S-type pyocins presumably creating increased pyocin resistance with little extra costs (23). The diversity of S-type pyocins displayed by some of the clinical isolates did not proportionally translate to better survival in the face of competition.…”

“…This suggests that A031 kills in an R-pyocin independent manner, and indeed, F-pyocins and/or phage are also likely to be important in P. aeruginosa strain competition. Strains can also become sensitive to their own R-pyocins through altered LPS (23), and this further complicates the picture. More work is required to unravel all the factors which drive interactions between P. aeruginosa strains.…”

General and condition-specific essential functions of Pseudomonas aeruginosa

“…Two additional essential genes (PA0125 and PA4674) also encode putative antitoxins of RelBE-and HigBA-like toxin-antitoxin pairs (45), and two others inhibit pyocin expression (prtR) or activity (imm2). In the absence of any of these inhibitory functions, toxin or pyocin activity presumably kills producer cells (43,46,47 , an essential reaction that compensates for the absence of an asparginyl-tRNA synthetase in P. aeruginosa (48). The process is not essential in mammals (49) and represents a potential drug target.…”

Bacteriocins and the assembly of natural Pseudomonas fluorescens populations

“…We measured the cell density of cultures at A600 (SpectraMax), standardized each culture to an OD of 0.3 and diluted this 10-fold in fresh KB media. Cultures were incubated for 12 h before we added 100 lL of 0.02 mg lL À1 mitomycin C (Sigma, UKltd), a strong inducer of bacteriocin production, and incubated for a further 4 h (Pentermann et al, 2014). We then centrifuged cultures at~13000 g for 10 min, obtaining a clear, cell-free supernatant by filter sterilizing with a 0.02-lm filter and storing at À20°C until required.…”