Abstract
The brain-gut–microbiome axis is an emerging area of study, particularly in vertebrate systems. Existing evidence suggests that gut microbes can influence basic physiological functions and that perturbations to the gut microbiome can have deleterious effects on cognition and lead to neurodevelopmental disorders. While this relationship has been extensively studied in vertebrate systems, little is known about this relationship in insects. We hypothesized that because of its importance in bee health, the gut microbiota influences learning and memory in adult bumble bees. As an initial test of whether there is a brain-gut–microbiome axis in bumble bees, we reared microbe-inoculated and microbe-depleted bees from commercial Bombus impatiens colonies. We then conditioned experimental bees to associate a sucrose reward with a color and tested their ability to learn and remember the rewarding color. We found no difference between microbe-inoculated and microbe-depleted bumble bees in performance during the behavioral assay. While these results suggest that the brain-gut–microbiome axis is not evident in Bombus impatiens, future studies with different invertebrate systems are needed to further investigate this phenomenon.
Highlights
The relationship between the gut and brain, known as the gut–brain axis, is an emerging area of study, especially in vertebrate systems
We found that withholding microbe inoculations from newly emerged bees that we kept in sterile conditions results in a greatly reduced gut microbiota without the use of antibiotics [22], making the bumble bee microbiome well-suited for behavioral assays
We have presented here the first study, to our knowledge, that has examined whether a brain-gut-microbiome axis exists in bees
Summary
The relationship between the gut and brain, known as the gut–brain axis, is an emerging area of study, especially in vertebrate systems. Recent research has shown that gut microbes can contribute to this gut–brain axis and that perturbations to the microbial community can have detrimental effects on learning, memory, and neurological disorders in vertebrate hosts [3,4]. These relationships have received increasing attention in vertebrate systems, understanding the mechanisms for them remains difficult due to the large diversity of symbionts that vertebrates can host [5]. Because they host a more tractable number of microbial symbionts [6], insects have been suggested as an ideal system to study the brain-gut-microbiome axis [7]
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