Researchers at Alexander Fleming’s BSRC in Greece have optimized a method to detect DNA traces in honey, revealing the species with which honey bees interact. This collaborative work, led by researcher Dr. Solen Patalano, enabled the monitoring of bee diet variation throughout the year, revealing the microbiota of bees in a non-invasive way, as well as identifying the pathogenic species they encounter. The research study, published in the journal Molecular Ecology Resources, and while still in its early exploratory phase, may revolutionize the way we understand honey bee ecological niches.
Why is it important to understand the ecological status of the bee?
What determines the ecological niche of an organism is a delicate balance of interactions and adaptations with other species that coexist in the same habitat. By pollinating trees and flowers, honey bees exploit a large number of flowering plant species for their food sources and growth. On the other hand, bee colonies are weakened when environmental conditions favor the proliferation of pathogenic species such as Varroa mites. Therefore, the dynamics of bee ecological niche species is inextricably linked to the type of bee habitat and its seasonal changes.
In the face of the increasing changes in the structure of agricultural areas and the effects of climate change, the ecological niches of bees are becoming more vulnerable. A better understanding of the dynamics of interactions between bees and surrounding species will help identify periods and areas of risk for bees. This is especially important in rural and agricultural environments, where species interactions affect crop productivity. It’s compelling how much of our food and survival depends on the proper functioning of tiny insects!” Anastasios Galanis, first author of the study, stated.
Honey, a unique indicator of environmental plant diversity
Honeybees return nectar and pollen from the flowers they forage and then place it in the cells of the hive to allow enough water to evaporate. Through this process, honey comes into contact with different organisms and therefore contains DNA from different species, collectively called environmental DNA (eDNA). It originates from forage plants, bee gut bacteria and potential hive pathogens. An optimized method now published called “Direct Shotgun Metagenomics” involves the sequencing and comprehensive identification of eDNA fragments present in honey. As explained by Galanis: “Designing and testing a bioinformatics pipeline tuned for honey metagenomic data allows us to increase sensitivity and specificity; Therefore, we can be quite confident about identifying specific species.”
In this study, researchers analyzed several honey samples from an apiary located in a typical Mediterranean landscape. They identified more than 40 species of plants, all reflecting the plant diversity surrounding the hives. “What was very striking was to see how plant eDNA abundance varied across the seasons, perfectly reflecting the behavioral adaptations of foraging that follow plant flowering,” Dr. Patalano said. The researchers also compared different honey samples using melissopalinology (using the shape of pollen grains to determine characteristics). Beyond the high complementarity of these two analyses, this study showed that the metagenomic approach also revealed non-pollinating foraging behaviors, such as foraging for pine honeydew, an important food source for bee survival in early fall.
Disease forecasting and spread of pathogenic agents
Contrary to popular belief, the ecological status of bees is beyond plants. In the analyzed honey samples, the researchers showed a higher number of bacterial eDNA species, the vast majority of which originated from microorganisms that are harmless and make up the main species of the bee microbiome. “Like the human gut microbiome, the gut microbiome of bees is an important element for their health,” explains Dr. Patalano. We already know that environmental stressors, such as pesticides, can seriously damage gut microbial communities and increase the risk of bee diseases. But how it works remains largely unknown.” With this, the researchers provide evidence that the honey metagenomics approach allows studying the diversity of the gut microbiome without the need to sacrifice the bees.
The researchers also looked for the presence of eDNA from potential pathogens. They found that Varroa mite eDNA footprints in honey directly corresponded to observed hive infestations. This is a promising sign that this research can eventually be used to monitor and predict diseases and pathogens in large-scale studies.
“In the future, this work may have very important consequences for humans. If we want to ensure ecosystem services such as fruit and vegetable pollination while maintaining species biodiversity, we must also protect the health of bees. Our challenge is to establish biological monitoring. strategies to identify the most suitable ecological niches for all pollinators,” concluded Dr. Patalano.
Reference: Galanis A, Vardakas P, Reczko M, et al. Honey bee, microbiota and pathogens with metagenomics Mol Ecol Res. doi:10.1111/1755-0998.13626