Genetic analysis of a stress response that protects the bacterium Pseudomonas aeruginosa from aminoglycoside antibiotics

As the need for new antibiotic therapies grows, it is increasingly important to understand how bacteria protect themselves from antibiotics. Comprehensive genomic screens have revealed functions whose role in antibiotic resistance was previously unknown. These functions can potentially be exploited by drug therapies to enhance antibiotic action. This work investigates genes in the pathogen Pseudomonas aeruginosa responsible for intrinsic resistance to aminoglycosides, a valuable class of antibiotics for treating lung infections. It focuses on an uncharacterized transcriptional regulator (AmgRS) that controls a major resistance mechanism. Transcriptional and mutational analyses are used to investigate the mechanism of resistance. We hypothesize that AmgRS protects cells from aminoglycoside-induced stress by inducing protective functions, and a group of AmgRS-regulated genes are identified, consisting of candidate resistance genes. Genetic dissection of this regulon implicates three functions that operate in a partially redundant manner to provide AmgRS-mediated aminoglycoside resistance. The findings indicate that proteolysis at the cytoplasmic membrane is a primary function of the AmgRS response. We suggest that its role in aminoglycoside resistance is to protect the membrane from mistranslated proteins whose production is induced by aminoglycoside treatment. A general role in protecting the membrane from stress is indicated by the pleiotropic phenotype of amgRS mutants.