Screening of microbes, isolation, genetic manipulation, and physiological optimization of Brevibacterium helvolum to produce and excrete thymidine and deoxyuridine in high concentrations

Analogues of deoxypyrimidines are used in the treatment of a variety of human ailments. Azidothymidine, or AZT, is one such analogue used to treat AIDS. Thymidine is the precursor of AZT, and its cost contributes to the high price of AZT. Attempts are being made to isolate and genetically manipulate microbes that can produce and excrete this compound in high concentrations. To this end, 145 different microbial species from Zeneca and the American Type Culture Collection were screened. Moreover, soil samples were collected from 36 different sites in England, and microbes from these samples were isolated and screened. From approximately 25,000 isolates screened as single colonies and from 4,000 in liquid cultures, a strain of Brevibacterium helvolum showed the most promising results. Pyrimidine metabolic pathways of this bacterium were worked out, the isolate was genetically manipulated, and physiological conditions were optimized to increase the production of thymidine and deoxyuridine. These mutants of B. helvolum are considered to be of commercial importance.