This grant proposal focuses on four distinct yet interrelated aspects of the molecular pathogenesis of human mycoplasma disease, emphasizing surface membrane properties of Mycoplasma pneumoniae and Mycoplasma genitalium. The first describes our attempts to understand cytadherence by characterizing the mycoplasma adhesins implicated in host cell parasitism. Various techniques will be employed including column chromatography, amino acid sequencing, oligonucleotide determinations, recombinant DNA methodology, mutant analysis, and gene transfer systems. The second focuses on specific lactoferrin-binding membrane components (receptors) of M. pneumoniae and their possible role in tissue colonization and/or virulence. These are recent observations, and data suggest the potentially important role of the lactoferrin-M. pneumoniae interaction in the metabolic integrity of these pathogens. The third will utilize a variety of already generated (and to be generated) immunological probes to study ultrastructural relationships among the mycoplasma adhesins and lactoferrin- binding membrane components by immunoelectron microscopic analysis using antibody-colloidal gold reagents. The fourth attempts of develop models for assessing virulence of M. genitalium. The current dependence on humans and non-human primates severely restricts virulence testing of wild-type strains and potential avirulent mutants of M. genitalium.