Multiple micro-organisms in chalkbrood mummies: evidence and implications

Abstract

SUMMARYThe pathogenic fungus Ascosphaera apis is the causative agent of the brood disease chalkbrood in honey bee (Apis mellifera) larvae. Infected, hardened larvae—in a powdered form—have been used to inoculate experimental honey bee colonies. While attempting to grow a pure isolate of A. apis from chalkbrood infected larvae, we discovered (via Gram staining and sequencing of the 5.8S rDNA region) that the inoculum also harbours many species of bacteria and additional species of fungi. Some of these fungi have been identified previously as antagonists of A. apis. It is not surprising that bacteria and fungi grow on dead bees; however, our data indicate that previous experiments intended to study the effects of A. apis in honey bees have rather studied the response of honey bees to a cocktail of fungal and bacterial agents. Accordingly, our results indicate that previous research on the A. apis-honey bee disease system was not specific to A. apis and raise the possibility that the observed honey bee response may have been muted, magnified, or both.