We are pursuing these studies as follows: a) Extending investigation of MarA and its regulon into other organisms as well as further defining the MarA regulon and MarR function in E. coli; b) Continuing efforts to obtain increased resolution of 2D and 3D crystals of the purified TetA(B) protein; studying additional mutants of the protein to understand its function; c) Focusing on the first step of acquisition of multidrug resistance (mdr) in mammalian cells. d) Examining the role in soil colonization of the regulatory protein AdnA and its regulon in Pseudomonas fluorescens; possible role of quorum sensing relatively to infection by P. aeruginosa; e) Analyzing resistance data collected from households which do or do not use antimicrobial cleaning products.