The influence of caging, bedding, and diet on the composition of the microbiota in different regions of the mouse gut.

Countless studies have identified differences between the gut microbiota of humans affected with myriad conditions and healthy individuals, and animal models are commonly used to determine whether those differences are causative or correlative. Recently, concerns have arisen regarding the reproducibility of animal models between institutions and across time. To determine the influence of three common husbandry-associated factors that vary between institutions, groups of weanling mice were placed in either static or ventilated microisolator caging, with either aspen or paperchip bedding, and with one of three commonly used rodent chows, in a fully crossed study design. After thirteen weeks, samples were collected from multiple regions of the gastrointestinal tract and characterized using culture-independent sequencing methods. Results demonstrated that seemingly benign husbandry factors can interact to induce profound changes in the composition of the microbiota present in certain regions of the gut, most notably the cecum, and that those changes are muted during colonic transit. These findings indicate that differences in factors such as caging and bedding can interact to modulate the gut microbiota that in turn may affect reproducibility of some animal models, and that cecal samples might be optimal when screening environmental effects on the gut microbiota.