[Quantity of exogenous linear DNA absorbed by E. coli cells treated with Ca2+ cations]

The amount of linear chromosomal DNA entering Ca2+-treated Escherichia coli K 12 cells was estimated from the degree of degradation of exogenous DNA by intracellular nucleases. At least 40% of DNA adsorbed by the cells in the nucleaso-resistant form (45 MD/cell) was discovered to be as intracellular. No significant difference was found between single- and double-stranded DNA.