Bee colonies use a shared chemical defence system

Honey and propolis are among the strongest defences against pathogens in a beehive, while bees’ own tissues and secretions target some microbes more selectively, ERR reports, citing a new study.

Researchers in Australia examined 24 bee colonies, testing honey, propolis, pollen, wax and bee tissues to see how they affected different bacteria and fungi. They found that honey and propolis killed nearly all the pathogens tested.

Other defences were more selective. Fat bodies in nurse bees produce substances that attack bacteria harmful to bees while leaving harmless environmental microbes alone. Bees are also less aggressive against fungi, because some yeasts help ferment pollen into food.

The researchers said honey uses hydrogen peroxide to fight bacteria, while plant flavonoids play that role in propolis.

The strength of the colony’s defences depends on its surroundings, the study found. Bees foraging only on uniform farmland may not collect a sufficiently diverse range of plant compounds to maintain strong protection. The findings were published in ISME Communications.