Accumulating evidence has suggested that the community of microbes in the gastrointestinal tracts of most organisms have a significant impact on the host's health and well-being. New research has indicated that the gut microbiome is also influencing the brain function of some animals. The study, which identified a species of gut bacteria in bees that seems to change the insect's behavior, has been published in Nature Communications.
In this study, the researchers exposed bees to differently colored artificial flowers and tastes. Five colors were put in a sweet sugar solution while another five colors were put in a solution that contained a bee repellant called quinine. This test allowed the researchers to see when the bees learned which colors would give them a tasty treat and which would not. Another test assessed whether the bees remembered this lesson three days later.
When bees carried higher levels of the gut bacterium Lactobacillus apis, their recall ability was better compared to bees that has lower levels of L. apis. When bumblebees consumed food that was spiked with L. apis, their memories lasted longer compared to bees that did not consume L. apis in their (controlled) diet.
The scientists could sequence all the microbial DNA in the bees to see what microbes each carried, and this information was assessed along with the memory tests.
The cognitive ability of bees can vary, and their microbiomes are small. The variations in their microbiomes are likely due to a variety of environmental factors, such as pollination, nest condition and material, activity level, pathogen exposure, and social interactions. This study indicated that gut microbes seem to have a causative impact on memory.
"Our results suggest not only that the natural variation in the amount of a specific gut bacterium effects memory, but also show a causal link, that by adding the same bacterial species to a bee's diet can enhance their memories," said lead study author Dr. Li Li, a postdoctoral researcher at Jiangnan University. "Further research will be required to determine if and which bacteria species might have the same effect in humans. But our work has shone a bright light on this possibility."
"This is a fascinating finding that could apply to humans as well as to bees. Our findings add to growing evidence of the importance of gut-brain interactions in animals and provide insights into the cause of cognitive differences in natural bumblebee populations," added study co-author Professor Lars Chittka of Queen Mary University.
Sources: Queen Mary University of London, Nature Communications