A new study led by Taichi Suzuki, a joint assistant professor at Arizona State University’s Biodesign Institute and College of Health Solutions, has found that the transmission of a mammal’s microbiome can influence behavior in just four generations. The research was published in Nature Communications and involved collaboration with scientists from Max Planck Institutes, Rutgers University, and Cornell University.
The team investigated how artificial selection affects both the host and its microbiome. Suzuki explained that this is an emerging topic in evolutionary biology and domestication. To test whether changes in physiology or behavior could be caused by the microbiome alone, researchers performed fecal transplant experiments using two distinct microbiomes on germ-free mice.
“To identify which aspects of physiology or behavior were most influenced by the microbiome, we performed fecal transplant experiments using two distinct microbiomes and compared a wide range of traits in germ-free mouse recipients,” Suzuki said. “To our surprise, behavior — especially activity level — showed the strongest microbial influence, far exceeding effects on morphological traits such as body weight or size.”
The results showed that mice receiving microbiomes from low-activity donors became less active themselves. The bacterium Lactobacillus was identified as having a significant effect.
“We found that a metabolite produced by Lactobacillus, indolelactic acid (ILA), plays a key role in influencing behavior,” Suzuki said. “Although ILA itself does not easily reach the brain, by calming the immune system and lowering inflammatory signals that travel to the brain, it can indirectly affect mood, activity and behavior.”
This relationship between gut microbes and behavior is known as the gut-brain axis. According to Suzuki, his team’s work provides experimental evidence that behavioral changes due to selection can be mediated solely through microbial transmission.
“There are many evolutionary theories proposing that the microbiome plays a role in adaptation to rapid environmental and climate changes,” he said. “This work provides experimental support for those ideas.”
Suzuki noted that house mice have migrated with humans from Western Europe to the Americas over 200 years and have shown adaptation differences depending on climate.
“House mice migrated with humans from Western Europe to the Americas over the past 200 years,” Suzuki said. “In this short evolutionary period, mice in the Americas have already shown evidence of adaptation, differing in body size and behavior depending on whether they live in cold or warm climates.”
His team demonstrated these behavioral differences could emerge through selection on the microbiome alone.
“We demonstrated that high-activity behavior, characteristic of ancestral mice from Western Europe (likely reflecting higher metabolic demands in colder climates), can change to low-activity behavior (as seen in warm-climate populations in Brazil) simply by selecting mice with low activity and transferring the microbiome across four generations,” he said.
The findings suggest that adaptation mediated by microorganisms may allow animals—and possibly humans—to adjust more quickly to environmental changes than genetic evolution alone would permit.
“Just as conservation genetics considers genetic diversity, incorporating microbial diversity and microbiome-based approaches can advance fields ranging from conservation and domestication to biomedical research,” Suzuki said.
Currently, his group is studying wild rodent populations across Arizona’s Sky Islands region to further understand how microbial diversity supports natural adaptation.
Suzuki also pointed out possible applications beyond evolution: “The possibilities are endless,” he said. “Rather than offering a single or a few probiotic strains for everyone, it may one day be possible to engineer a microbiome from a person’s own microbial community, growing it in a bioreactor or animal model, selecting for desired functions and then using that community or selected strains for personalized treatment.”
He cautioned that while this research marks progress for animal studies of engineered microbiomes, further work is needed: “This is the first study to demonstrate how microbiome engineering can work in animals, and further studies are needed to replicate these results across different traits and systems,” he said. “The cost of microbiome engineering remains high when using animal models, so developing scalable, high-throughput systems that mimic the gut environment will be a key step toward translating these findings into microbiome-based therapies or interventions.”
Arizona State University has been recognized for its innovative approach for eight consecutive years according to U.S. News & World Report rankings (link).
