FACTORS INFLUENCING GASTROINTESTINAL MICROBIOTA

The intestinal microbiota is affected by a number of factors, such as antibiotics, diet, and inflammation[4-18]. A number of studies have reported a high degree of similarity in the intestinal microbiota between members of the same family but a low degree of similarity between heterozygous mice despite being housed in the same cage[9,14,19]. The intestinal microbiota of mice fed standard low- in-fat nutrients has been shown to change within a few weeks with particularly great changes in the composition of Bacteroidetes and Firmicutes species. After mice returned to a low-fat diet, a particularly significant reduction in Mollicutes, a species of Firmicutes, was observed[9,20]. Similar changes have observed with diets high in fat, particularly in obese people, genetically obese mice, and obesity-resistant mice[9,14,21]. Transfer of colon microbiota from mice fed a high-fat diet to mice fed a low-in-fat diet has been shown to accelerate tumor growth suggesting diet-induced changes in the colon microbiota may have a synergistic effect with genetic factors on tumor development[22]. Diet-related changes in intestinal microbiota have also been shown to be associated with colorectal cancer[23].