Distribution of restriction endonucleases among some entomopathogenic strains of Bacillus sphaericus

The restriction enzyme BspTI, an isoschizomer of HaeIII (recognition site GGCC), has been detected in eight strains of serotype 5a5b and two serotype 3 strains of the entomopathogenic bacterium Bacillus sphaericus. Strains from other serotypes contained the enzymes BspTII and BspTIII, which digested pBR322 DNA into similar banding patterns after agarose gel electrophoresis but differed in their susceptibility to methylation of the substrate. Strains from serotypes 9, 25 and 26a26b were lacking in restriction enzyme activity. There was little correlation between phage typing and restriction enzyme activity, suggesting that restriction and modification are not responsible for phage specificity among entomopathogenic B. sphaericus strains.