Friend or foe: Phenotypic variation of Aspergillus flavus strains within the context of the honey bee hive environment across the Midwest region of the United States of America

Aspergillus species occupy a diversity of niches within the honey bee (Apis mellifera) hive environment. The best-documented niche is as a causal agent of the fungal disease “stonebrood,” Aspergillus flavus. Additionally, non-aflatoxigenic strains of A. flavus are implicated as mutualists within the hive environment; however, no direct evidence supports this assumption. Previous research indicates that a newly isolated beebread-derived non-aflatoxigenic A. flavus strain (AFBB) is more tolerant of in-hive abiotic stress than other non-aflatoxigenic (AF36) and pathogenic strains and suggests possible adaptation to the honey bee hive environment. The non-aflatoxigenic nature of the AFBB strain is derived from a STOP codon in the polyketide synthase gene associated with aflatoxin B1 production. However, the new strain was isolated from a single honey bee colony, providing little insight into the wider ecological role of the beebread-derived strain. Thus, I aim to broaden the study of A. flavus in beehives by investigating the frequency of occurrence of A. flavus strains demonstrating similar phenotypic characteristics as the AFBB strain across various honey bee hive environments across the Midwest. Through the implementation of various selective measures, including growth on selective A. flavus media, PCR-validation of the strain’s inability to produce aflatoxin, and disk diffusion assays with propolis-derived chemical components, I will attempt to isolate A. flavus strains with similar phenotypic characteristics as the AFBB strain. The identification and characterization of other “AFBB-like” strains from other honey bee hive environments may suggest possible ubiquity within the hive environment and may indicate a potential mutualistic ecological relationship.