Host strain for the expression of a target gene cloned in the pTYB vectors. Carry a chromosomal copy of the T7 RNA polymerase gene inserted into lacZ gene and thus under the control of the lac promoter. In the absence of IPTG induction expression of T7 RNA polymerase is suppressed by the binding of lac I repressor to the lac promoter. Deficient in both lon and ompT proteases.
