A new insertion sequence from Sinorhizobium meliloti with homology to IS 1357 from Methylobacterium sp. and IS 1452 from Acetobacter pasteurianus

Abstract

The insertion sequence IS Rm8 was identified by sequence analysis of the cryptic plasmid pRmeGR4b of Sinorhizobium meliloti GR4. IS Rm8 is 1451 bp in length and carries 22/24-bp terminal imperfect inverted repeats with seven mismatches and a direct target site duplication of 3 bp. IS Rm8 carries a unique open reading frame whose putative protein showed significant similarity to the insertion sequences IS 1357 and IS 1452, isolated from Methylobacterium sp. and Acetobacter pasteurianus, respectively. Two copies of this IS element were found in strain GR4; one of them is linked to plasmid pRmeGR4b, whereas the other is localized out of the non-pSym plasmids. In S. meliloti field populations IS Rm8 shows a limited distribution (50% of the strains tested carry the IS element), with a copy number ranging from 1 to 6.