Characterization of IS2112, a new insertion sequence from Rhodococcus, and its relationship with mobile elements belonging to the IS110 family.

A new insertion sequence (IS2112) was identified in the genome of the 1-haloalkane-utilizing bacterium Rhodococcus rhodochrous NCIMB 13064. The insertion element is 1415 bp long, does not contain terminal inverted repeats, and is not flanked by directly repeated sequences. IS2112 belongs to the IS110 family of transposable elements, and forms a separate subfamily, along with IS116. Two copies of IS2112 were found in R. rhodochrous NCIMB 13064 and one, two or three copies of a similar sequence were detected in five other 1-haloalkane-degrading Rhodococcus strains. There were no sequences homologous to IS2112 found in the 1-haloalkane-degrading 'Pseudomonas pavonaceae' 170 and Rhodococcus sp. HA1 or in several Rhodococcus strains which do not utilize haloalkanes. IS2112 was originally found in plasmid pRTL1 of R. rhodochrous NCIMB 13064, which harbours genes encoding utilization of 1-haloalkanes, and was located 5 kbp upstream of the haloalkane dehalogenase gene (dhaA). Although the second copy of IS2112 in strain NCIMB 13064 was also present on the pRTL1 plasmid, these sequences do not apparently comprise a single composite transposon encoding haloalkane utilization. An analysis of derivatives of NCIMB 13064 revealed that IS2112 was involved in genome rearrangements. IS2112 appeared to change its location as a result of transposition and as a result of other rearrangements of the NCIMB 13064 genome.