This application is for a pilot research project by a new investigator. Pathogenic bacteria, like all microbes, live in a complex environment that includes fluctuations in the chemical and physical environment, a variety of other microbes with which to compete for nutrients, and have the added burden of dealing with a host that has sophisticated systems that can prevent bacterial growth and/or survival. The long-term objective of this research is to elucidate the mechanisms used by Neisseria gonorrhoeae to respond to its environment. The ultimate goal of these studies is to identify novel targets for therapeutic agents that would disrupt the initial events in a gonococcal infection such that the organism would never go on to produce disease. The short-term goal of this research, which this proposal represents the beginning of, is to develop a system using DNA arrays and a tissue culture model for gonococcal infection in order to examine global gene expression and identify potential regulators that respond to host cell contact. The results of these initial experiments are expected to lead to future studies in which these systems will be examined in more detail to eventually characterize regulatory networks involved in the response of N. gonorrhoeae to its environment. The specific questions to be addressed are: 1. What are the changes in global gene expression in gonococci upon contact with host cells? And 2. What are the regulatory networks that are involved in the modulation of gene expression in gonococci upon contact with host cells? Preliminary studies indicate that adherence of gonococci to host cells results in differential gene expression in the bacterium. These results will be expanded upon to identify the regulatory systems that are involved in this response. Since there are few well characterized virulence regulatory systems identified in the pathogenic Neisseriae, the results of these experiments will provide new and vital information in understanding how these pathogens respond to their environment, leading to further experiments to determine how this is related to the disease process. Additionally, the tools developed here will be of general use in characterizing gene expression in this important pathogen in response to any environmental change, drug treatment, or genetic background.