The role of NrtR in AmrZ regulation process in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen which creates acute and biofilm associated chronic infections. Biofilm is a mode of growth in which bacteria live as a community and its formation is a complex and a highly regulated process. This project focuses on one of the pathways that affects biofilm formation, specifically on the mechanism by which the flagella motor complex MotAB is controlling the levels of the central biofilm regulator AmrZ. AmrZ has an enormous impact on biofilm formation - it regulates alginate production, represses psl expression and was recently found to effect motility as well. MotAB was previously found in our lab to affect the degradation of AmrZ. In WT, AmrZ levels are extremely low at planktonic phase, and in the ΔmotAB strain AmrZ tends to accumulate. Using a genetic screen we targeted the nrtR gene that was found to affect AmrZ levels. When mutated, AmrZ levels in the ΔmotAB strain are decreased. In addition, NrtR affects swarming motility and biofilm formation as well. ΔmotAB strain is characterized with low biofilm formation and high swarming abilities. The ΔmotABΔnrtR strain forms extensive biofilm and has no swarming ability, opposite to ΔmotAB strain. The role of NrtR in P. aeruginosa is not fully understood and requires further investigation. Characterizing the AmrZ formation and degradation cascade effected by NrtR would lead us to a better understanding of biofilm formation processes and will promote us towards innovative solutions for the phenomenon.