Use of suppression subtractive hybridization to identify genetic differences between differentially virulent genotypes of Paenibacillus larvae, the etiological agent of American Foulbrood of honeybees.

Paenibacillus larvae is the causative agent of American Foulbrood of honeybees, a fatal brood disease not only killing infected larvae but also lethal to infected colonies. Recently four different genotypes of P. larvae (enterobacterial repetitive intergenic consensus I-IV) have been described and it was shown that these genotypes also differ in phenotype, especially in virulence. To unravel the genetic differences between these four genotypes, suppression subtractive hybridization was used. From 106 analysed clones, 92 represented genotype-specific sequences, whereas 14 sequences turned out to be specific only for the particular strain used as tester in the subtraction. Nearly half of the sequences (46%) could only be annotated based on poorly characterized sequences. The remaining sequences corresponded to categories related to metabolism, especially secondary metabolite biosynthesis, transport and catabolism, to information storage and processing, and to cellular processes. In particular, we could show that the P. larvae genome contains genes and/or giant gene clusters coding for antibiotics, and we identified the first P. larvae toxin, a member of the family of adenosine diphosphate-ribosyltransferases.