A team of scientists from Jiangnan University, Queen Mary University of London and the University of Oulu has identified a causal link between an increased levels of the symbiotic gut bacteria Lactobacillus apis and improved long-term memory in buff-tailed bumblebees (Bombus terrestris): the bumblebees with more of this type of bacteria in their guts had a better memory than individuals with fewer bacteria; the insects that ate food containing more of this species were also found to have more long-lasting memories than individuals with normal diets.
Proposed pathway between intestinal glycerophospholipid production and memory enhancement: based on metagenomic and metabolomic analyses, Li et al. suggest that increased levels of Lactobacillus apis (and other Firm-5 species which similarly contain many genes for the PTS sugar transport pathway) will cause increased sugar metabolism, which will lead to the production of more glycerophospholipids; these glycerophospholipids are then transported into the hindgut and are rapidly secreted into the hemolymph (perhaps helped by an increase in mGlu2 receptors); they are transported to the brain via the bee’s open circulatory system, with attached metabolites, leading to improved structure and function of neural and synaptic membranes, thereby promoting better memory. Purple shapes: genes that positively correlated with long-term memory; rectangles: genes found in all three analyses (analyses based on genes mapped to the whole gut microbiota, Firm-5 and Lactobacillus apis). Ovals: genes found in whole gut microbiota and Firm-5 analyses. Rounded rectangles: remaining memory-correlated genes. Gray shapes: genes which did not correlate with long-term memory. Blue arrows: sugar metabolism. Red arrows: glycerophospholipid metabolism. Purple arrows: the increase or decrease of metabolites after Lactobacillus apis supplementation. Image credit: Li et al., doi: 10.1038/s41467-021-26833-4.
“Bees’ cognitive abilities vary across individuals and they possess a relatively small community of gut microorganisms compared with mammals, making them ideal models to explore the role of specific gut symbiotic bacteria on individual cognitive variations in natural populations,” said Jiangnan University’s Professor Wei Zhao and colleagues.
“Similar to the human gut microbiota, bee gut bacteria are specific to the host gut. These bacteria can be transmitted from one individual to another via foraging on flowers and certain social interactions within the nest.”
“The bee hindgut has the highest abundance of bacteria and is dominated by five core bacterial species clades.”
“Each bacterial species within this core group are thought to be symbiotic and possess distinct metabolic functions linked to mutualistic interactions with the host, as well as biofilm formation, and carbohydrate breakdown.”
“We set out to test whether individual cognitive variation across bumblebees might stem from microbiota-gut-brain interactions, and specifically ask which and how specific gut microbes might drive these cognitive differences in normal, healthy bumblebees.”
To test the bumblebees’ memory and learning abilities, the researchers created different colored artificial flowers: five colors were associated with sweet sucrose solution and the other five with a bitter tasting solution containing quinine, a repellent for bees.
The scientists then observed how quickly the bees were able to learn which colors were associated with a sugar reward, and if they were able to retain this information in a follow-up test three days later.
By sequencing gut samples from the bees, they were then able to compare individual differences in bumblebees learning and memory abilities with the levels of different bacteria found in their gut.
To confirm that the numbers of Lactobacillus apis in the gut were directly responsible for the observed differences in memory, the authors added these bacteria to the bumblebees’ diet and measured their responses to the same task.
“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 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,” said Professor Lars Chittka, a researcher at Queen Mary University of London.
“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.”
“It’s amazing to find out the specific memory-enhancing bacteria species,” Professor Zhao added.
“The results further validate our belief that we may improve our cognitive ability via the regulation of gut microbiota.”
The findings were published in the journal Nature Communications.
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L. Li et al. 2021. Gut microbiome drives individual memory variation in bumblebees. Nat Commun 12, 6588; doi: 10.1038/s41467-021-26833-4
Source link: https://www.sci.news/biology/lactobacillus-apis-long-term-memory-bumblebees-10307.html
