Several copies of the same insertion sequence are present in alpha-hemolytic plasmids belonging to four different incompatibility groups

Alpha-hemolytic plasmids belonging to four different incompatibility groups contained several copies (two to six) of the same DNA sequence. This sequence was capable of illegitimate recombination and thus behaved as an insertion sequence element. Its size (1.9 kilobases) and restriction enzyme cleavage map suggested that it was different from previously described insertion sequence elements.