Nucleotide sequence of a repetitive element isolated from Leptospira interrogans serovar hardjo type hardjo-bovis

Abstract

A repetitive element from the genome of Leptospira interrogans serovar hardjo type hardjo-bovis ('L. hardjo-bovis') was identified, cloned and sequenced. Similar sequences were shown by hybridization to be encoded by a further eight of 32 other leptospiral serovars tested. An undefined number of repetitive elements were located in the L. hardjo-bovis genome; sequence degeneracy of the elements was observed and no significant open reading frames were identified within the AT-rich (60%) 1467 bp repetitive element. The termini encoded a GC-rich 8 bp repeat motif and two variants showed rearrangements centred on these motifs. The nucleotide sequences of the chromosomal regions flanking the repetitive elements were determined but showed no similarities, with one exception which had a GAAC repeat directly adjacent to both termini. Similar hybridization patterns were shown by Southern transfers of L. hardjo-bovis total genomic digests probed with the repetitive element. Oligonucleotide primer pairs designed from sequences internal to the repetitive element and adjacent chromosomal regions were used in polymerase chain reaction experiments. With one primer pair all L. hardjo-bovis isolates, but no other serovar, gave identical amplified products. Evidence that the repetitive element may have derived from an acquired insertion sequence that is now inactive and chromosomally fixed is discussed.