Natural isolates of Bacillus thuringiensis display genetic and psychrotrophic properties characteristic of Bacillus weihenstephanensis

Aim:  To determine the potential of Bacillus thuringiensis , known primarily for its entomopathogenicity, to be a psychrotolerant contaminant of stored products. Methods and Results:  We determined the genetic properties and diversity of cold‐adapted isolates of B. thuringiensis based on (i) the presence of cspA , a genetic determinant that confers psychrotolerance in Bacillus weihenstephanensis , (ii) 16S rRNA genes, and (iii) pulse‐field gel electrophoretic (PFGE) genome profiles. We assessed the pathogenic potential of these isolates based on whether they harboured various combinations of known toxigenic‐associated determinants ( nheA , hblA , cytK ). Of 36 nonclonal B. thuringiensis cultured from soil and milk, 21 harboured cspA , and of these, 16 (76%) were psychrotolerant and possessed genetic signatures typical of psychrotrophic Bacillus species. The majority of psychrotolerant isolates contained various combinations of nheA , hblA , and cytK . Conclusion:  Our results show that natural isolates of psychrotolerant B. thuringiensis occur in soil and milk, and suggest that psychrotolerance is determined by cspA . Significance and Impact of the study:  The presence of cspA in combination with nheA , hblA , and cytK could be of concern if commercial products are contaminated with strains that harbour these determinants.