Sensitivity of Escherichia coli to viral nucleic acid. XVI. Temperature conditions for Ca2+-dependent dna uptake in Escherichia coli.

Properties of Ca2+- or Ba2+-dependent transfection and transformation in Escherichia coli were examined, using phi X174 replicative-form (RF) DNA and plasmid DNA. For the transfection and transformation, a heat pulse step was dispensable and the yield of transfectants was, in most E. coli strains, rather reduced by the heat treatment. The heat pulse step was also detrimental for the transformation of certain strains such as lipopolysaccharide mutants, The first stage of the DNA uptake process (formation of DNA . recipient cell complex) was dependent on low temperature and Ca2+ ion. A substantial amount of the complexed RF-DNA was released from the bacteria, by washing with a chilled Tris buffer. Although a RF-DNA . cell complex was formed even at 37 degree C or in chilled 0.05 m MgC12, the complex did not yield transfectants.