ISMh2, a novel insertion sequence-like element associated with nifA from Mesorhizobium huakuii

Sequence analysis of the nifA gene, including its 5' flanking region, of Mesorhizobium huakuii revealed the presence of a novel IS-like element called ISMh2. It is 828 bp in length and possesses two imperfect terminal inverted repeats of 14 bp with only one mismatch. The putative transposase encoded by ISMh2 is composed of 204 amino acids. In comparison with other insertion sequences ISMh2 likely belongs to the IS6 family. Multiple copies of ISMh2 were detected in the genome of M. huakuii 159 by Southern hybridization. RT-PCR analysis showed that nifA and ISMh2 cotranscribed. Attempts to detect the transposition ability of ISMh2 were unsuccessful.