The MarR-Type Regulator PA3458 Is Involved in Osmoadaptation Control in .

is a facultative human pathogen, causing acute and chronic infections that are especially dangerous for immunocompromised patients. The eradication of is difficult due to its intrinsic antibiotic resistance mechanisms, high adaptability, and genetic plasticity. The bacterium possesses multilevel regulatory systems engaging a huge repertoire of transcriptional regulators (TRs). Among these, the MarR family encompasses a number of proteins, mainly acting as repressors, which are involved in response to various environmental signals. In this work, we aimed to decipher the role of PA3458, a putative MarR-type TR from . . Transcriptional profiling of PAO1161 overexpressing showed changes in the mRNA level of 133 genes; among them, 100 were down-regulated, suggesting the repressor function of PA3458. Concomitantly, ChIP-seq analysis identified more than 300 PA3458 binding sites in . The PA3458 regulon encompasses genes involved in stress response, including the operon, which is divergent to . This operon encodes an asparagine synthase, a GNAT-family acetyltransferase, and a glutamyl aminopeptidase engaged in the production of N-acetylglutaminylglutamine amide (NAGGN), which is a potent bacterial osmoprotectant. We showed that PA3458-mediated control of - expression is required for the adaptation of . growth in high osmolarity. Overall, our data indicate that PA3458 plays a role in osmoadaptation control in .