The Escherichia coli Stock Center maintains a collection of around 7,000 genetically defined stock cultures of the bacterium, E. coli strain K-12, and distributes upon request about 5000 cultures of these mutants each year. Requests come from scientific investigators and teachers in the fields of microbial genetics, molecular biology, biochemistry, biophysics, medical research, recombinant DNA technology and related fields who are working in academic and governmental laboratories, non-profit research institutes, industrial laboratories and recombinant DNA firms. The Stock Center archives information on the histories, derivations and genotypes of mutant derivatives of E. coli K-12 and also acts as a center for information on the identification and genetic mapping of these organisms. The Stock Center's curator, Dr. Barbara Bachmann, publishes revisions of the E. coli K-12 linkage map and pedigrees of E. coli mutants. The Center also coordinates the assignment of gene symbols, allele numbers and strain designations. To facilitate the above functions, during this award the Center will computerize its extensive records and search procedures. New stocks will be added to the collection in response to needs as new types of mutants are isolated and new techniques of genetic analysis are developed.