I have traditionally used 20 mM L-Arabinose to induce lambda red on pKD46. I have also noticed that r-m+ strains grew exceptionally slow during linear transformation. I decided to trace the cause of this defect by comparing their growth along with that of wild type plus or minus ampicillin (used to hold the plasmid) and plus varying concentrations of L-Arabinose. Results: 20 mM L-Arabinose inhibits growth of the r-m+ strain and inhibits yield of both strains. Ampicillin exacerbates the growth inhibition of the r-m+ strain, but not of the wild type. Experiment and data.
Host Restriction of UNI Cassettes
Our UNI CamR, KanR & SpecR cassettes all contain sites for endogenous LT2 restriction endonucleases. I tested the efficiency of transformation of these cassettes into a wild-type background (TT22970) and an r-m+ background (TT22971). My results are consistent with the hypothesis that UNI CamR cassettes are degraded by wild type LT2 when introduced by electroporation. Test description and data.
The RADIO 