Integrating GC/TOF exposome profiling and genetic disease screening to provide a holistic perspective on honey bee health

PCR targeted disease screening light on potentially unexplored mechanisms of infection, biochemical feedback, and increased susceptibility to disease using gas chromatography/quadrupole time-of-flight mass spectrometry (GC/QTOF) for discovery-based exposome profiling, and semiquantitative polymerase chain reaction (sqPCR) screening for the common gut fungal pathogen. Nosema ceranaeand apis was used to assess the disease state of the hives. A total of 6 mL of RNase-free water was added to 30 bees collected from each hive. The bees were homogenized with a sterile mortar and pestle. DNA was extracted from a 150-μL aliquot using a phenol:chloroform:isoamyl alcohol mixture. Hive samples were run in triplicate and the ratios of each Nosema species to reference gene were averaged. Hive infection was considered as a categorical variable. Samples from each hive were also collected for GC/QTOF analysis. More than 2350 chemical features were identified in the MS data, and the spectral library searches successfully annotated 73% of these compounds. When the exposome profiles are grouped based on unsupervised hierarchical clustering, exposome profiles associated with disease load are observed. These observations support the authors' hypothesis that chemicals and metabolites unique to the presence of a Nosemainfection can be identified and possibly serve as chemical biomarkers for the presence of this disease.