Enzymatic sorting of bacterial colonies on filter paper replicas: detection of labile activities

To utilize autoradiographic colony-sorting techniques (C. R. H. Raetz, Proc. Natl. Acad. Sci. U.S.A. 72:2274-2278, 1975) for the isolation of mutants with unstable enzymes, we report a new desiccation-induced lysis method, compatible with low temperatures. Furthermore, a general, two-step protocol is presented for clonal detection of hydrolytic reactions. The advantages of these critical modifications are demonstrated with the membrane enzymes glycerol 3-phosphate acyltransferase and cytidine 5'-diphosphate-diglyceride hydrolase.