CLONING AND SEQUENCE-ANALYSIS OF A NOVEL INSERTION ELEMENT FROM PLASMIDS HARBORED BY THE CARBOFURAN-DEGRADING BACTERIUM, SPHINGOMONAS SP CFO6

Sphingomonas sp. CF06 (a member of the alpha group of Proteobacteria) was isolated from a Washington soil by enrichment on the insecticide c arbofuran as a sole source of carbon and energy. This strain has been shown to harbor five plasmids, at least some of which are required for catabolism of carbofuran. Rearrangements, deletions, and loss of indi vidual plasmids resulting in the loss of the carbofuran-degrading phen otype were observed following treatment with heat or introduction of T n5. Several putative insertion sequence elements of different sizes we re cloned from these plasmids by trapping in pUCD800, a positive selec tion vector for isolation of transposable elements. Three of the most common putative IS elements (designated IS1412, IS1487, and IS1488) in the clone library were of different sizes and cross-hybridize with ea ch other. An element hybridizing with IS1412, IS1487, and IS1488 was m obilized during growth of CF06 at 42 degrees C. and inserted into one of CF06's plasmids (pCFO4), corresponding to a deletion in the plasmid and a loss of catabolic function. IS1412 was completely sequenced and its sequence analyzed. IS1412 is 1656 bp in length and possesses term inal partially matched inverted repeats of unequal length (17 and 18 b p). In addition, IS1412 contains an open reading frame which encodes a putative transposase with significant homology to the putative transp osases of IS1380 from Acetobacter pasteurianus, HRS1 from Bradyrhizobi um japonicum, and IS1247 from Xanthobacter autotrophicus. These relate d IS elements form part of a family of common IS elements distributed among members of the alpha group of the Proteobacteria. (C) 1997 Acade mic Press.