Obese mouse to GF mouse: Microbiota transplantation experiments utilizing genetically obese ob/ob mice [66],CONV-R mice fed a Western diet [67], and mice lacking the Toll like receptor 5 [68] have demonstrated that colonization with an obesity-associated gut microbiota results in an increased gain in adiposity relative to colonization with a gut microbiota harvested from lean controls. The gene discussed is TLR5; the disease is obesity due to melanocortin 4 receptor deficiency.