The food available to the microbiome varies during the day, according to the feeding schedule and to the kind of food that is provided to the mice. Because the

The food available to the microbiome varies during the day, according to the feeding schedule and to the kind of food that is provided to the mice. Because the generation time of the bacteria is very short, e.g. fractions of an hour, it is normal for the quantities of each kind of bacteria to vary during the day, following the fluctuations in the concentrations of various nutrients in the intestine. For a constant microbiome composition, one would have to feed the mice with exactly the same food at the same hours each day, and sample the microbiome also at fixed hours that are the same each day.