The long-term goals of this project are to elucidate host-symbiont relationships and to formulate a comprehensive theory for the integration of newly acquired symbionts into host cells leading to the acquisition of new cell components and changes in cellular phenotypic characters. In the recently established amoeba-bacteria symbiosis, symbiotic bacteria were originally harmful to the hosts but changed to required cell components within a few years, bringing about many changes in cell characters. The specific aims are to test the following 4 hypothesis: 1) That the symbiont-produced 29-kD protein is a factor required by host amoebae for their survival, 2) that the symbiosome membrane has a "fusion-preventing" component which is responsible for the prevention of lysosomal fusion with symbiosomes, 3) that the plasmid DNAs of symbiotic X-bacteria code for cell-surface components of X- bacteria that confer them resistance to digestion and their infectivity and 4) that the X-bacteria came from one of the bacterial strains normally living in the amoeba culture. These studies will use immunocytochemical methods with monoclonal antibodies, gene cloning, nucleotide sequencing, gel electrophoresis, micrurgy, and other biochemical and molecular-biological techniques. Expected results will not only enhance our understanding of the mechanisms for the establishment and maintenance of stable endosymbiosis, but also will provide insight into the origin of new cell components in eukaryotic cells and cellular character changes. In addition, some of the results might be applicable in therapeutic research on diseases caused by infective agents, in which such agents avoid digestion by the host cells probably by similar mechanisms. //
