1. Department of Gastroenterology, Heilongjiang Provincial Hospital, Harbin, Heilongjiang 150036, P.R. China
2. Department of Gastroenterology, The First Affiliated Hospital of Jiamusi University, Jiamusi, Heilongjiang 154002, P.R. China
3. Center for Computational and Integrative Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02114, USA
4. Department of Hygienic Microbiology, Public Health College, Harbin Medical University, Harbin, Heilongjiang 150081, P.R. China