IS1032 from Acetobacter xylinum, a new mobile insertion sequence

IS1031 elements constitute a family of related insertion sequences (IS) in Acetobacter xylinum strains. A new IS1031-related element, IS1032, was isolated from A. xylinum ATCC 23770. Southern hybridization analysis showed that one or more sequences similar to IS1032 are present in most of the A. xylinum strains examined. In addition, one copy was detected in Acetobacter aceti ATCC 15973. The transposition of IS1032 was evident from the appearance of an extra insertion in a spontaneous exopolysaccharide-negative mutant of A. xylinum ATCC 23770. IS1032 consists of 916 bp and has imperfect terminal inverted repeats of 14 bp (IR-Left) and 16 bp (IR-Right). A 3-bp target sequence is duplicated upon insertion. IS1032 displays a single open reading frame, encoding a putative 276-amino-acid protein sharing 58% identity with the corresponding protein encoded by IS1031. Thus, IS1032 is a member of the IS1031 family in A. xylinum. A striking degree of nucleotide sequence similarity between IS1032 and ISRm4 from Rhizobium meliloti was found. Furthermore, the IS1031-family transposases also display stretches of amino acid sequence similarities with putative transposases encoded by IS elements from other species.