What is already known
The gut microbiota has been linked to neurodevelopment, with young germ-free mice showing neurological and behavioral deficits. An altered microbial composition has also been associated with a child’s temperament and with cognitive difficulties in autism. However, it’s unclear how gut microbes contribute to cognition.
What this research adds
Researchers compared the gut microbiota and the cognitive skills of healthy 6-month-old infants, and found an association between a microbial enzyme and the infants’ cognition. Transferring gut microbes from infants to germ-free mice revealed that memory is a transmissible trait. Compared to mice receiving the microbiota of infants with lower-than-average cognition scores, those receiving gut microbes from infants with higher-than-average scores displayed higher levels of Phaeicola, Bacteroides and Bifidobacterium, which have been previously linked to cognition, as well as different ratios of specific bacterial metabolites in a brain region involved in object memory.
Conclusions
The findings show that specific gut microbes and their metabolites affect cognition and memory when transplanted into germ-free mice.
Gut microbes play an important role in infant development, and have been linked to a child’s growth as well as their neurodevelopment. Now, researchers have found that specific gut bacteria and their metabolites affect cognition and memory when transplanted into germ-free mice.
The findings, published in Cell Host & Microbe, suggest that the gut microbiota can influence cognitive performance.
Previous work has shown that germ-free mice or mice with an altered gut microbiota display neurological and behavioral deficits. A disrupted microbial composition has also been associated with a child’s temperament and with cognitive difficulties in autism. However, it’s unclear how gut microbes contribute to cognition.
To assess the microbiota’s potential to influence behavioral outcomes, Tomás Cerdó at the University of Córdoba in Spain and his colleagues analyzed the gut microbes and cognitive performance in healthy 6-month-old infants and in baby mice.
Cognition effect
The microbiota of healthy 6-month-olds was dominated by Bacillota, followed by Bacteroidota, Pseudomonadota, Actinomycetota and Fusobacteriota. However, the microbiota of infants with higher-than-average cognition scores showed higher diversity than that of infants with lower-than-average scores. The microbiota of infants with higher-than-average cognition scores also had increased levels of Bacteroidota and reduced abundances of Bacillota, the researchers found.
Next, the team profiled the proteins expressed within the infants’ gut microbiota. The microbiota of infants with lower-than-average scores was enriched in proteins involved in intracellular trafficking, and it was depleted in proteins involved in carbohydrate transport and metabolism.
Instead, the only protein to be significantly enriched in the microbiota of infants with higher-than-average cognition scores was histidase, an enzyme that breaks down the amino acid histidine. The activity of histidase was also higher in infants with higher-than-average cognition scores compared with those with lower scores.
Histidine is the precursor of the neurotransmitter histamine, and both histidine and histamine have been reported to influence human cognition, the researchers say.
Transmissible memory
Transferring gut microbes from infants to germ-free mice revealed that memory is a transmissible trait. Compared to mice receiving the microbiota from infants with lower-than-average cognition scores, those receiving microbes from infants with higher-than-average scores displayed higher levels of Phaeicola, Bacteroides and Bifidobacterium, which have been previously linked to cognition.
Compared to mice that received the microbiota of infants with lower scores, animals that received microbes from infants with higher scores also had lower levels of histidine in their feces as well as different ratios of other bacterial metabolites in a brain region involved in object memory.
“Overall, these findings reveal a causative role of gut microbiota on infant cognition, pointing at the modulation of histidine metabolite levels as a potential underlying mechanism,” the authors say.
