Humans have hundreds of germ species in their guts—most bees have just nine.
Look inside the guts of a honeybee worker from practically anywhere on the planet, and you’ll most certainly find only nine species of bacteria.
The amazing constancy of this microbial bundle across the planet—similar across species, including sociable bumblebees—indicates that bacteria play a critical role in honeybee survival. Bees with healthy microbial partners have more complicated social ties and even different brain chemistry than bees with sterile guts, according to research published earlier this week in the journal Nature Ecology and Evolution.
In many mammals, the gut biome—the population of bacteria, fungus, and other microorganisms that dwell inside us—plays a potentially enormous but unexplained function. It may even influence human mind. “The gut-brain axis is really intriguing from an evolutionary standpoint, because gut symbionts were most likely present when the earliest neurological systems formed,” says Joanito Liberti, main author of the study and an evolutionary biologist at the University of Lausanne in Switzerland. There are some indications that microorganisms may influence our behavior, but unlike honeybees, we have hundreds of creatures inside us, making it difficult to link cause and effect.
And the importance of gut bacteria was highlighted in this study. “This [result] really suggests that the gut microbiota may be critical to the hive’s functioning,” Liberti says. The need of gut microbes in bee survival may also explain why bees are vulnerable to human hazards, particularly agricultural toxins.
Honeybees are particularly well-suited to microbial investigations because, unlike human offspring, they are born sterile. When bees reach adulthood and begin interacting with other members of the hive, they acquire their microbial cargo. The researchers can raise blank-slate bees without using antibiotics by taking days-old grubs from the hive and culturing them in sterile conditions. In half of the cases, bacteria from the lab’s microbial bank were reintroduced. The rest were born infertile.
During the 10-day trial period, the sterile bees showed no visible indicators of suffering, such as poor flying or collapsing. They just did not socialize as much as their microbially full siblings. They were significantly less likely to brush heads with other bees, which signifies trading food or information in bee terminology. “They also interacted with the rest of the group more randomly, more equitably,” Liberti says. “It appears that the gut microbiota caused these bees to form ‘friendships.'”
Egalitarian bees may appear to be a good thing, but according to Liberti, a colony with several specialized connections is really better at negotiating the intricacies of the world. “Not everyone is doing everything at once,” he explains. “If you’re doing brood care, it doesn’t matter if foragers discovered a food patch—you want information about the brood.”
When the researchers peered inside the bees, they discovered changes in the function of their DNA. A third of the 60 compounds examined in bee brains were less prevalent in the infertile population. Four specific amino acids found in bacterial-bees were found to be involved in neurotransmission or brain fuel supplies. Memory, vision, smell, and taste genes were all altered in brain tissue—basically, the microbiota messed with the replicating machinery that turned those genes into chemicals.
“Perhaps the microbiome has no direct effect on bee survival,” Liberti speculates. “However, if they’re not working effectively in their brain, they’ll be less efficient at storing the food they acquire, generating the honey they require, and this will eventually have an influence on the hive’s survival.”
This may assist to explain why wild and domestic bee populations are under such strain. High doses of a popular herbicide have been proven in studies over the last decade to damage honeybee microbiomes. The weedkiller may impair learning and sensory abilities without actually killing the bees.
While some agricultural exposures may affect insects indirectly through the microbiome, depending on the amount, they can also have direct consequences, according to Liberti. A study he co-authored earlier this year discovered that persistent, low-level pesticide and herbicide exposure messed up honeybee metabolisms without affecting their microbiomes. Many popular pesticides, herbicides, fungicides, and even medicines have already been proved to directly kill honeybees.
It’s possible that we’ve been unknowingly affecting the microbiome, which is another important aspect of honeybee life.
Leave a Reply