The Impact of Environmental Factors on Honey Bee Microbial Health

Our knowledge of the essential bacteria found in honey bee guts and hive environment has greatly increased recently, demonstrating the importance of these microorganisms to bee health. We still don't fully understand, however, how the surrounding ecosystem affects the microbial communities inside the colony. It turns out that the microbial composition within the hive is significantly shaped by environmental microbes, such as those found in soil, flowers, and water. The microbial community within each hive is dynamic due to the continuous exposure of hives to these environmental microbes. It is a vibrant system that is constantly impacted by altered flowering plants through the seasons, landscape elements, and beekeepers' colony management practices.

The microbial community within hives mirrors the local environment.The microbial signature that each hive develops is primarily determined by its immediate surroundings. For example, the microbes that bees bring back to the hive through nectar and pollen gathering are significantly influenced by the kinds of flowers they visit. Different flowers host different microbial communities.Instead of simply passing through, these microorganisms frequently integrate into the hive's microbial ecosystem, impacting bee health, promoting disease resistance, and boosting colony productivity as a whole. This microbial signature varies in different locations , those close to the mountains have different microbial signature than those close to the sea. 

Bees come into contact with microbes in a variety of ways. They acquire bacteria and yeasts from flowers while foraging, which subsequently infiltrate their bodies and the food supplies of the hive. A wide variety of advantageous and occasionally dangerous microorganisms are transported by nectar and pollen, which act as microbial gateways. Bees also encounter microorganisms from soil particles, water sources, and even the air while foraging. They spread these microorganisms to combs, food storage, and all  hive surfaces as they return to the hive. The hive's internal microbial community is shaped  by this continuous microbial inflow.

Bees do more than simply carry nectar back to the hive after gathering it. They start a fermentation process that turns nectar into honey with the help of a variety of bacteria and yeasts. This fermentation aids in its preservation. Another microbially rich food source that is vital for feeding and nourishing developing larvae is beebread,  fermented pollen kept inside the hive .It's interesting to note that a large number of microbes that are present in beebread and the honey stomachs of bees are also found in the nectar that they gather, indicating that pollinators, plants, and hive members share microbes.

In fact, bees' social behavior fosters intimate microbial relationships. Microbes are spread by contact, food sharing, and resource sharing .Royal jelly, a unique glandular secretion produced by worker bees, is nutrient-dense substance and contains antimicrobial elements that support and "vaccinate" the  larvae. Royal jelly, which protects against illness and promotes the spread of healthy bacteria throughout the colony, is every day applied to the queen's midgut when nurse bees feed her. In order to keep the queen and growing larvae from getting sick, this social immunity is crucial. 

Honeybee queens "vaccinate" their larvae against certain diseases by nature. In order to prime the larvae to fend off infections, the queen bee transfers immune-boosting proteins to her developing eggs. The basis of this natural vaccination is a protein known as vitellogenin, which transports immune elicitors ,such as bits of bacteria, from the queen's body to the developing eggs. Pathogens or substances that stimulate the immune system are consumed by the queen bee. These are subsequently transferred to the developing eggs after being bound to vitellogenin in her adipose body. The larvae have some immunity against certain diseases because they are already prepared to identify and react to these pathogens when they hatch.As a naturally occurring mechanism within the honeybee colony, this process is a type of immune priming.

Beyond hive products, the bees themselves are part of the microbial ecosystem of bee nests. They contain a variety of microbial communities that are vital for protection, immunity, and digestion. The gut microbiome is the most well-characterized of these, especially in honey bees, where a core group of bacterial species has co-evolved with their hosts over millions of years. Numerous species aid in the breakdown of intricate plant polysaccharides, the detoxification of toxic secondary metabolites from floral resources, and the maintenance of immune defense pathways, which offer crucial defense against infections. Bees have microbial communities on their exoskeleton, which make up the cuticular microbiome, in addition to their gut. With many microbes generating antimicrobial compounds that aid in preventing pathogen colonization, this outer microbial layer acts as an extra line of defense.

The hive itself operates similarly to a small, intricate ecosystem that is frequently referred to as a "superorganism." It keeps the pH, humidity, temperature, and other environmental parameters in delicate balance. The benign microbial life it fosters acts antagonistically with pathogens, inhibiting their spread.The hive environment is home to a rich and diverse community of microbes, including beneficial bacteria, transitory microbes from flowers, and potential pathogens, all of which interact within this tiny world, whereas the bacteria found in adult bee guts are comparatively limited in diversity. According to recent research, there are roughly thirteen major bacterial strains that coexist there and cooperate to safeguard the bees from pathogens.

A hive's surroundings have a significant impact on the microbial community within it . Bees actively spread bacteria by touching different surfaces nearby, licking the surfaces of their hives, and applying propolis, a resinous material they gather from plants. The antimicrobial qualities of propolis itself aid in the suppression of pathogenic microorganisms and the promotion of advantageous ones. The fact that flower-derived microbes like Lactobacillus and Bacillus species frequently enter the hive and the bees' digestive tracts highlights how much the environment shapes and influences their microbial life.

Through a variety of methods, beekeepers may unintentionally change the microbial communities inside their hives. These include using herbicides around the hives , applying in-hive treatments like antibiotics, and managing hive conditions that affect the bees  overall health like scraping out the propolis that bees accumulate. The bee microbiome and hive microbiome overall are impacted by varroa mite treatments and frequent applications of miticides.By providing substitutes of  pollen or feeding with sugar surup, beekeepers can affect the microbial communities and change the gut microbiome's composition. Bees' capacity to digest food, obtain nutrients, and fend off illnesses can all be impacted by changes in their microbiome. The immune system of bees and the general health of the colony depend on a healthy microbiome.

Evangelia Mavridis

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