Figure 3.

Gnotobiotic mouse models of cancer are crucial for probing the importance of microbiota in chemoprevention. Image of a gnotobiotic mouse facility. Mice are maintained in isolators (n=6 are pictured) where the air is filtered with a specialized HEPA filtration system (white cylinders). Everything that enters the isolators (e.g., cages, bedding, food, water) is autoclaved in advance (usually inside of metal canisters) and enters through an airlock system (circular structures) after the exterior surface is sprayed with antiseptic. The mice are handled using a glovebox apparatus (not pictured, located on other side of isolators). The mice can be maintained germfree (i.e., devoid of all microbiota) or they can be colonized with one or more specific microbiota introduced by gavage. The mice can be “humanized” by colonizing them with human-derived microbiota, including from disease cases versus controls, to interrogate the function of human microbiota in a rigorously controlled manner. A typical isolator holds up to ~12 cages. To prevent contamination, only one combination of microbiota can be used per isolator and regular microbiology testing is necessary (e.g., fecal samples and swabs analyzed by Gram staining, PCR, etc.).