Bacteria Group leader National Agriculture and Food Research Organization (NARO) Tsukuba, Ibaraki, Japan
European foulbrood, an important bacterial disease of honey bee brood, can be found in most areas in the world where apiculture is practiced. The causative agent, Melissococcus plutonius, had long been regarded as a fastidious organism; however, non-fastidious variants of this species (designated as atypical M. plutonius) were found in Japan in 2009. Although the morphology of those unusual strains was similar to that of traditionally well-known M. plutonius strains, the atypical strains were genetically very different from most M. plutonius strains isolated previously and highly virulent to individual bee larva. In this presentation, I would first like to talk about the background of the discovery of atypical M. plutonius in Japan and why I started European foulbrood research, and then will share what I have learned about atypical M. plutonius so far and what questions remain to be answered.