Mucosa-Associated Bacteria in the Human Gastrointestinal Tract Are Uniformly Distributed along the Colon and Differ from the Community Recovered from Feces

The human gastrointestinal (GI) tract harbors a complex community of bacterial cells in the mucosa, lumen, and feces. Since most attention has been focused on bacteria present in feces, knowledge about the mucosa-associated bacterial communities in different parts of the colon is limited. In this study, the bacterial communities in feces and biopsy samples from the ascending, transverse, and descending colons of 10 individuals were analyzed by using a 16S rRNA approach. Flow cytometric analysis indicated that 10(5) to 10(6) bacteria were present in the biopsy samples. To visualize the diversity of the predominant and the Lactobacillus group community, denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene amplicons was performed. DGGE analysis and similarity index comparisons demonstrated that the predominant mucosa-associated bacterial community was host specific and uniformly distributed along the colon but significantly different from the fecal community (P < 0.01). The Lactobacillus group-specific profiles were less complex than the profiles reflecting the predominant community. For 6 of the 10 individuals the community of Lactobacillus-like bacteria in the biopsy samples was similar to that in the feces. Amplicons having 99% sequence similarity to the 16S ribosomal DNA of Lactobacillus gasseri were detected in the biopsy samples of nine individuals. No significant differences were observed between healthy and diseased individuals. The observed host-specific DGGE profiles of the mucosa-associated bacterial community in the colon support the hypothesis that host-related factors are involved in the determination of the GI tract microbial community.

人类胃肠道（gastrointestinal tract，GI）的黏膜、肠腔与粪便内，定植有复杂的细菌群落。既往研究多聚焦于粪便中的细菌，因此人们对结肠不同部位黏膜相关细菌群落的认知仍较为有限。本研究采用16S rRNA测序技术，对10名受试者的粪便样本，以及升结肠、横结肠、降结肠的活检样本中的细菌群落进行了分析。流式细胞术检测结果显示，每份活检样本中含有10^5至10^6个细菌。为解析优势菌群与乳杆菌属群落的多样性，研究人员对16S rRNA基因扩增子开展了变性梯度凝胶电泳（denaturing gradient gel electrophoresis，DGGE）分析。DGGE分析与相似性指数对比结果表明，黏膜相关优势细菌群落具有宿主特异性，且在结肠内呈均匀分布，但与粪便细菌群落存在显著差异（P < 0.01）。乳杆菌属特异性电泳图谱的复杂度，低于反映优势菌群的电泳图谱。在10名受试者中，有6名的活检样本内类乳杆菌细菌群落与粪便样本中的群落结构相似。研究人员在9名受试者的活检样本中，检测到与加氏乳杆菌（Lactobacillus gasseri）16S核糖体DNA序列相似度达99%的扩增子。健康受试者与患病受试者之间未观察到显著差异。本次研究观察到的结肠黏膜相关细菌群落的宿主特异性DGGE图谱，支持“宿主相关因素参与调控胃肠道微生物群落构成”这一假说。