The purpose of the study was to examine the role of the elements of PmrA/PmrB two-component system in the global regulation of gene expression in L.pneumophia during axenic growth. Towards this goal pmrA and pmrB isogenic mutants were constracted in L. pneumophila strain AA100 using allelic exchange. Gene expression profiles were generated for both mutants during their growth in axenic media and compared to the corresponding gene expression profiles in the ancestral strain. Overall design: PmrA mutant: three independently axenically grown samples were analyzed in mid-exponential and postexponential phases of growth. PmrB mutant: three independently axenically grown samples were analyzed in mid-exponential and postexponential phases of growth. A100 strain: three independently axenically grown samples were analyzed in mid-exponential and postexponential phases of growth as a reference for the PmrA and PmrB mutants.