Comparison of IS1, IS2 and IS3 copy number in Escherichia coli strains K-12, B and C.

The number of copies of IS2 and IS1 in the chromosomes of five Escherichia coli K-12 strains and E. coli B and E. coli C has been determined by hybridization. Among these strains, IS1 copy numbers range from 4 to 19 and IS2 copy numbers range from 0 to 12. IS2 is present once in the E. coli B chromosome, but it is absent from E. coli C. The copy numbers of IS3 in the same seven E. coli strains range from 4 to 6.