The epidemiology of members of the Mycobacterium avium, M. intracellulare, and M. scrofulaceum (MAIS) group is significant both because of their human pathogenicity and their presumed environmental origin. Accurate description of MAIS epidemiology will provide a model for investigations of these and other environmental pathogens. That AIDS and other immunocompromised patients have increased risk of MAIS infections, underscores the importance of knowledge of MAIS epidemiology. The proposed research seeks to employ recently developed techniques for rapid isolation, speciation and identification of potentially pathogenic MAIS to identify the environmental sources and characterize the pathways of human infection. Approaches to those long term goals include: (1) isolation, identification and enumeration of potentially pathogenic MAIS in various environmental compartments (e.g. soil, water, dust, aerosols) and correlation of MAIS numbers with environmental physiologic (e.g. pH and organic matter) and biologic (e.g. plankton and fecal enterics) features of the samples, (2) identification of physiologic features (e.g. adaptations to high light flux and fluctuating pH) of MAIS which influence their geographic distribution by measuring H2O2 and O2- killing and membrane pH and proton gradients, (3) determination of the relationship between cell surface molecules (e.g. proteins) and hydrophobicity as it relates to aerosolization of MAIS from natural waters and human infection, employing hexadecane partitioning, detergent polyacrylamide gel electrophoresis (PAGE), protease treatment and aerosolization measurements, (4) laboratory study of aerosol survival of MAIS in biosafety chambers under stimulated natural climates (e.g. temperature, relative humidity and sunlight), and (5) characterization of plasmid-genes involved in characteristics of potentially pathogenic MAIS (e.g. growth at 43 C, growth without oleic acid and albumin and transparent colony type) by plasmid DNA isolation and characterization by restriction endouclease digestion and Southern hybridization. From such studies, not only the environmental sources and pathways of human infection identified, but characteristics of MAIS organisms influencing pathogenicity will be identified.