Melissococcus plutonius is the causative agent of European foulbrood in honeybee larvae. This bacterium is a fastidious organism; microaerophilic to anaerobic conditions and the addition of potassium phosphate to media are required to grow it in culture. In Japan, however, in addition to M. plutonius strains with typical cultural characteristics (typical M. plutonius), M. plutonius-like organisms, with characteristics seemingly different from those of typical M. plutonius, have been isolated from diseased larvae with clinical signs of European foulbrood. DNA-DNA hybridization and 16S rRNA gene sequence analysis demonstrated that M. plutonius-like organisms (atypical M. plutonius) were taxonomically identical to M. plutonius. However, unlike typical M. plutonius strains, atypical M. plutonius strains were not fastidious, and the addition of potassium phosphate was not required for normal growth. Moreover, only atypical M. plutonius strains, but not typical M. plutonius strains, grew anaerobically on sodium phosphate-supplemented medium and aerobically on some potassium salt-supplemented media, were positive for β-glucosidase activity, hydrolyzed aesculin, and produced acid from L-arabinose, D-cellobiose, and salicin. Although M. plutonius was previously thought to be homogeneous, our present results indicate that this species consists of at least two groups of strains, typical and atypical M. plutonius, which are phenotypically distinguishable.
(Bacterial and Parasitic Disease Research Division)
Arai R. et al. (2012) PLoS ONE 7(3): e33708