Cupric ion resistance as a new genetic marker of a temperature sensitive R plasmid, Rtsl in Escherichia coli.

A temperature sensitive kanamycin (Km) resistant R plasmid, Rtsl, was found to confer cupric ion (Cu²⁺) resistance on its hosts in $\text{Escherichia}\text{coli}$. At conjugal transfer, two kinds of segregants were obtained from Rtsl, i.e. Cu²⁺ resistant, Km sensitive and Km resistant, Cu²⁺ sensitive plasmids. Protein T existed in $\text{E.}\text{coli}$ cells harboring Rtsl or the Cu^rKm^s-plasmid. The inhibitory effect on the host cell growth at 43°C was observed with Rtsl⁺ or the Km^rCu^s-plasmid⁺ cells. A relationship between these Rtsl derivatives and Rtsl in $\text{Proteus}\text{mirabilis}$ which has been studied was discussed.