Mapping of insertion element IS30 in the Escherichia coli K12 chromosome

We identified seven phage clones containing the insertion element IS30 in a lambda phage library mini-set, which includes 476 clones carrying chromosomal segments that cover almost the entire chromosome of Escherichia coli K12 W3110 (Kohara et al. 1987). We could assign locations and orientations to four copies of IS30 (named is30A to is30D) on the W3110 chromosome by restriction analysis of phage DNAs containing them. These IS30s were present at the same locations in chromosomes of both W3110 and another E. coli K12 strain JE5519, and thus are assumed to be present in other E. coli K12 derivatives, including early isolates. Among the IS30 copies found, one (is30B) contained a large deletion and possessed only a 181 bp stretch of the right terminal region of IS30.