A 16S rRNA Gene Oligonucleotide Probe for Identification ofBacillus thuringiensisIsolates from Sheep Fleece

Abstract

Larvae of the Australian sheep blowflyLucilia cuprinaare susceptible to some strains ofBacillus thuringiensis,including some isolates from sheep fleeces from South Australia and Western Australia. Larvicidal strains ofB. thuringiensisinclude var.thuringiensis, tolworthi, darmstadiensis, morrisoni,andtoumanoffi.As part of an ecological study, a large number ofB. thuringiensisfleece isolates from untreated sheep and sheep previously treated with larvicidalB. thuringiensiswere screened for larvicidal activity. A ribotyping method to distinguish larvicidalB. thuringiensisjetted (sprayed) onto sheep from the naturalB. thuringiensisflora of the fleece was developed. A cloned fragment of the 16S rRNA gene used as a probe forB. thuringiensisDNA digested with restriction endonucleases enables separation ofB. thuringiensisserovars and separation within the serovarsthuringiensis, tolworthi,andkurstaki.The 16S gene probe method is useful for distinguishing between reisolates of larvicidalB. thuringiensisjetted onto sheep and the backgroundB. thuringiensispopulation present prior to jetting.