Читать книгу Honey Bee Medicine for the Veterinary Practitioner - Группа авторов - Страница 50

The recent discovery that bee venom, the collection of vasoactive peptides injected by worker bees using their stinger in defense of the colony, is found on the cuticle of worker bees as well as on the wax surface of the nest comb suggests that venom may play an antiseptic role in social immunity (Baracchi et al. 2011). Bee venom consists of a mix of biogenic amines, peptides, and proteins with neurotoxic action while also breaking down mast cells and stimulating the release of vasoactive substances. More recently, bee venom has been shown to have antimicrobial properties as well. Since there is a complete lack of venom peptides on the cuticle of drones and newly emerged bees, one can surmise that the venom found on the cuticle of worker bees is placed there by grooming behavior from the venom gland itself. Therefore, the allogrooming behavior of bees to remove pests and pathogens may be augmented by the defense provided by the neurotoxic peptides of bee venom (Figure 2.3).

Honey bees synthesize a variety of antimicrobial compounds in response to infection with microorganisms (Simone‐Finstrom 2017). One of the better‐known peptides produced from the cells of both vertebrates and invertebrates is defensin. A role in innate immunity has been suggested for defensins given their diverse activity against bacterial, fungal, and viral pathogens (Raj and Dentino 2002). One such defensin compound is royalisin isolated from royal jelly – the nurse bee secretion fed to young worker larvae and developing queen larvae. Royalisin has broad antibacterial and antifungal properties, even possessing inhibitory growth against Paenibacillus larvae, the causative agent of American foulbrood (Bíliková et al. 2001). It is likely that these protective antimicrobial peptides can boost immunity at the level of the colony since the compounds are transferred widely during trophyllaxis.

Figure 2.3 Allogrooming, or the grooming of one bee by another nestmate, is a form of social immunity that helps remove potential pathogens from the hive. Through the deliberate spread of bee venom, this regular grooming may also play a central protective role in biosecurity by acting as a cuticular form of antisepsis.

The transmission of microorganisms from one bee to another does not always result in the spread of pathogens and disease. On the contrary, many beneficial bacteria are transferred throughout the colony during the complex interactions of honey bee society. Socially transmitted gut microbiota helps protect honey bees from infection by hive pathogens. Worker honey bees lack a bacterial microflora at the time of emergence and the future microbiome community of an individual bee is dictated by contact with nurse bees, the hive environment, and through trophyllaxis (Powell et al. 2014). In an experimental model of bumble bees (Bombus terrestris), contact with nestmate fecal material upon pupal emergence was required for protection against a virulent trypanosome gut parasite Crithidia bombi (Koch and Schmid‐Hempel 2011). The community of microorganisms in colonies of honey bees and bumble bees is distinctive from that found in solitary bees and its role in providing a first line of defense against potential pathogens is an area that deserves more thorough investigation.

Figure 2.4 Tree saps or resins are collected from leaf buds and packed onto the worker bee's corbiculae for transfer back to the hive where other bees offload the resin, mix it with beeswax and enzymes, to make propolis or “bee glue.”