FIG. 4.

DNA polymerase I activity of wild-type M. dichloromethanicum DM4 and of the polA mutant. Shown is an autoradiogram of cell extract protein (100 μg) of wild-type strain DM4 (lane 1), mutant DM4-1445 (lane 2), and complemented mutant DM4-1445(pME8112) (lane 3), separated by SDS-PAGE in a gel containing nicked DNA, after incubation with dideoxynucleotides and α-³²P-labeled dCTP (see Materials and Methods). Lane M, prestained marker from the scanned gel; lanes 4 and 5, E. coli DNA polymerase I and Klenow fragment, respectively (0.02 U [∼0.1 ng] each).