Objective The effects of ulcerative colitis(UC)on microbial diversity in the rat gastrointestinal tract were studied to provide a reliable basis for treating ulcerative colitis. Method Rat UC models were set up with 2,4-Dinitrochlorobenzene plus acetic acid compound method. The total microbial DNA was extracted from intestine with CTAB-SDS method. Analyzing microbial diversity in the rats gastrointestinal tract by denaturing gradient gel electrophoresis(DGGE). Results Comparing the results among these three groups(model group,medicated group,normal control group),we found that the Shannon index of bacteria varied from 1.64 to 3.05 among different parts of digestive tract. The highest one was in colon,then was in stomach and the lowest one was in small intestine . As for Shannon index of bacteria in colon,the medical group with 3.05 was the highest,followed by model group with 2.98,normal control group with 2.95,which showed that the microbial diversity in colon changed by the colitis. From the sequence analysis results we found that the numbers of bacteroides,clostridium,prevotella,porphyromonas in stomach of rat increased after getting ulcerative colitis,while in colon the number of lactobacillus decreased and clostridium,porphyromonas increased. Besides,in small intestine some species of lactobacillus disappeared and some uncommon flora such as clostridium and Porphyromonas appeared. Conclusion In stomach,small intestine and colon of UC rat,the number of beneficial bacteria lactobacillus significantly decreases while clostridium,prevotella and porphyromonas increase,which may finally cause endogenous infection and be an important reason for ulcerative colitis.%目的：探讨溃疡性结肠炎对大鼠胃肠道微生物多样性影响，为治疗溃疡性结肠炎提供可靠依据。方法采用2，4-二硝基氯苯乙酸复合法对健康SD大鼠进行溃疡性结肠炎造模；运用CTAB-SDS法提取肠道微生物总DNA，通过PCR-DGGE分析溃疡性结肠炎大鼠之间胃肠道微生物多样性差异。结果溃疡组、用药组和正常组大鼠的消化道中，不同部位细菌Shannon指数变化较大（1.64~3.05），结肠中Shannon指数最高，其次是胃，小肠最低。在结肠，不同组的细菌多样性Shannon指数变化幅度不大，以用药组最高（3.05），其次溃疡组（2.98），正常组2.95，说明大鼠结肠在健康状态下细菌多样性最低，结肠炎后会发生一定的变化。此外，发现病变后的大鼠胃中拟杆菌属、梭菌属、普氏菌属、紫单胞菌属等厌氧细菌增加，病变后的结肠中乳杆菌属细菌明显减少，紫单胞菌属和梭菌属细菌明显增加；病变后小肠中部分乳杆菌种类消失，同时梭菌属和紫单胞菌属等不常见菌群的出现。结论溃疡性结肠炎大鼠胃、小肠、结肠中有益菌乳杆菌明显减少，普氏菌属、紫单胞菌属、梭菌属等明显增多，这些菌属可作为条件致病菌引起内源性感染，可能是造成溃疡性结肠炎的重要原因。
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