ISL1: a new transposable element in Lactobacillus casei

Abstract
Summary The genome structures of a temperate Lactobacillus phage, ϕFSW, and its virulent mutants, ϕFSVs, were examined by restriction, heteroduplex and nucleotide-sequence analyses. The results showed that two out of three ϕFSVs had the same 1.3 kbp insertion (designated as ISL1) at different positions in the ϕFSW sequence. ISL1 was 1,256 bp long and contained at least two long open reading frames of 279 and 822 bases on one strand. Inverted repeats were found at the termini of the ISL1 which was bracketed by 3 bp direct repeats of the ϕFSW sequence. From this evidence, we concluded that ISL1 was a transposable element in Lactobacillus casei.