The first aim proposes to establish mechanisms for the production and distribution of Tetrahymena thermophila cell lines for use by not-for-profit academic and government laboratories that study recombinant proteins. Tetragenetics will be responsible for the production of cell lines and material derived from these cell lines, and the Tetrahymena Stock Center, an NIH-funded resource housed in the Clark laboratory at Cornell University, will act as a portal for ordering, storing, and disseminating strains using the existing infrastructure of the Stock Center. The second specific aim includes efforts to develop improved vectors and cell lines for DNA transformation of T. thermophila. The Clark laboratory at Cornell will be responsible for the production of a genetically altered strain of Tetrahymena in which all or part of the ribosomal DNA locus is deleted within the transcriptionally silent, germline micronucleus. This will involve the use of standard recombinant DNA techniques to introduce an interruption in the gene using either drug selectable markers or the cre-lox technology. Once this cell line is established it will be used by Tetragenetics for further strain development and will also be made available to the not-for-profit community for basic research.