摘要目的:分析结肠癌与直肠癌患者肠道菌群的构成差异。方法:收集2018年7月至2019年1月于哈尔滨医科大学附属第二医院就诊的72例大肠癌患者粪便样本，将其分为结肠癌组和直肠癌组，均为36例。提取粪便样本DNA，并对其进行高通量测序。采用生物信息学方法分析两组患者肠道菌群多样性及菌群构成的差异，探讨差异菌群可能的促癌机制。结果:72例样本经过高通量测序，共获得原始序列2 356 560条，优质序列32 730条，样本序列平均长度主要集中在401~460 bp，对所有序列进行操作分类单元（OTU）物种分类学注释后，获得1 409个OTU。Alpha多样性分析结果提示，直肠癌组和结肠癌组Shannon指数分别为2.61±0.56和2.43±0.67，差异无统计学意义（ t=1.229， P=0.223）；Simpson指数分别为0.17±0.09和0.21±0.16，差异无统计学意义（ t=1.449， P=0.151）。组间差异分析和线性判别分析（LDA）显示：在门水平，厚壁菌门（Firmicutes）在直肠癌患者肠道中丰度更高（LDA值为4.67， P=0.014），变形菌门（Proteobacteria）在结肠癌患者肠道中更加富集（LDA值为4.49, P=0.042）；在纲水平，丙型杆菌（Gammaproteobacteria）丰度在结肠癌患者肠道中较高（LDA值为4.50， P=0.033），而Erysipelotrichia在直肠癌患者肠道中丰度更高（LDA值为3.50, P=0.035）；在目水平，Erysipelotrichales在直肠癌患者肠道中丰度更高（LDA值为3.50， P=0.035）；在科水平，紫单胞菌（Porphyromonadaceae）丰度在直肠癌患者肠道中更高（LDA值为3.97， P=0.033）。 结论:结肠癌与直肠癌患者肠道菌群构成存在明显差异，提示不同的菌群可能影响结肠癌和直肠癌的发展进程。

abstractsObjective:To analyze the composition differences of intestinal microbiota in patients with colon cancer and rectal cancer.Methods:The fecal samples of 72 patients in the Second Affiliated Hospital of Harbin Medical University from July 2018 to January 2019 were collected, and they were divided into colon cancer group and rectal cancer group, 36 cases in each group. DNA from fecal samples was extracted, and then high-throughput sequencing was performed on DNA. Bioinformatics was used to analyze the diversity and composition differences of intestinal microbiota between the two groups, and the potential cancer-promoting mechanisms of the differential flora were also discussed.Results:From high-throughput sequencing, 2 356 560 original sequences and 32 730 high-quality sequences were obtained from 72 samples. The average length of the sample sequence was mainly in the interval of 401-460 bp. And 1 409 operational taxonomic units (OTU) were acquired after OTU species taxonomy annotation of all the sequences. Alpha diversity analysis showed that Shannon index of the rectal cancer group and the colon cancer group was 2.61±0.56 and 2.43±0.67, respectively, and the difference was statistically significant ( t = 1.229, P = 0.223); Simpson index of the rectal cancer group and the colon cancer group was 0.17±0.09 and 0.21±0.16, respectively, and the difference was statistically significant ( t = 1.449, P = 0.151). Differences analysis of both groups and linear discriminant analysis (LDA) showed at the phylum level, Firmicutes were more abundant in the intestine of patients with rectal cancer (LDA = 4.67, P = 0.014), while Proteobacteria were more abundant in the gut of colon cancer patients (LDA = 4.49, P = 0.042). From the perspective of class level, the abundance of Gammaproteobacteria was higher in the intestine of patients with colon cancer (LDA = 4.50, P = 0.033), while the abundance of Erysipelotrichia was higher in the intestine of patients with rectal cancer (LDA = 3.50, P = 0.035). At the order level, the abundance of Erysipelotrichales was higher in the intestine of patients with rectal cancer (LDA = 3.50, P = 0.035); at the family level, the abundance of Porphyromonadaceae was higher in the intestine of patients with rectal cancer (LDA = 3.97, P = 0.033). Conclusion:The compositions of intestinal microbiota in patients with colon cancer and rectal cancer are significantly different, indicating that the different floras may contribute to the progression of colon cancer and rectal cancer.