Abstract
(1) Replication origin of E. coli chromosome labeled with 3H-thymidine was shown to be preferentially bound to rapidly sedimenting fractions even after a chase for three bacterial generations. (2) DNA extracted from rapidly sedimenting fractions of exponentially growing cells was shown to be rich in the ilv and thy segments as compared to the lac or his segments. These observations suggest that replication origin of E. coli 15T- is always bound to cell-membrane.
