|Genotype||lacZam trpAam rpsL lambda(bio252 cI857 ΔH1)|
Expression host for plasmids containing phage lambda's PL or PR promoter. Induction is obtained by shifting the culture from 28°C to 42°C. The resident lambda is a defective lysogen. ΔH1 removes part of cro and all genes to the right of it. bio252 removes all genes to the left of cIII. cI857 is ind-. At 42°C, N is expressed from the lysogen. As a consequence, transcription termination signals that might be present downstream from the PL promoter and the nutL site, as present on the pPL-series of plasmids, can be overridden. Useful for the expression of cloned genes carrying transcription terminators between the start of the gene and the insertion point.