A cold sensitive dnaA mutant of E. coli which overinitiates chromosome replication at low temperature.

A heat resistant mutant of E. coli dnaAts46 was isolated, which grows normally only at temperatures above 39 degrees. After a temperature shift from 42 degrees to 32 degrees the mutant overproduces DNA relative to protein. This is due to overinitiation of rounds of chromosome replication at low temperature, as indicated by hybridization and other experiments. The mutation is cotransduced by PI with ilv and could not be separated from dnaAts46 by transduction.