Morning or an evening person? It`s in your gut!

Patterns of diurnal activity differ substantially between individuals, with early risers (“larks") and late sleepers (“owls”) being extreme examples of individuals who present diurnal preferences, also termed “chronotypes”. Given the bidirectional associations that have been discovered in recent years between the circadian clock and gut microbiota, we hypothesized that the variation in chorotypes is associated with variability in gut microbiota function and composition. We samples feces from Drosophila strains that show extreme nocturnal and diurnal behavior and carried out 16S rDNA microbiota profiling using the Illumina MySeq sequencing platform. Comparison of the diurnal and nocturnal microbiome indicated that 20% of the variation among samples can be explained by the diurnal factor. Next, we cultured an Acetobacter strain that was found to be enriched in diurnal flies and fed it to nocturnal flies. Following this treatment, the chronotype of the flies became diurnal, demonstrating the causal role of the gut bacteria.

Inspired by our Drosophila studies, we have also profiled the gut microbiome composition of human, using metagenomic sequencing. The study, which consisted of 133 participants established a distinct signature associated with chronotype based on two bacterial genera, Alistipes (elevated in “larks”) and Lachnospira (elevated in “owls”). We identified three metabolic pathways associated with the early chronotype, and linked distinct dietary patterns with different chronotypes. The Lachnospira bacteria (which was also found to be elevated in nocturnal Drosophila) is known to synthesize butyrate, suggesting an important role for short-chain fatty acid (SCFA) in inducing late chronotypes.