Escherichia coli are mostly commensals but also contain pathogenic lineages. It is largely unclear whether the commensal E. coli as the potential origins of pathogenic lineages may consist of monophyletic or polyphyletic populations, elucidation of which is expected to lead to novel insights into the associations of E. coli diversity with human health and diseases. Using genomic sequencing and pulsed field gel electrophoresis (PFGE) techniques, we analyzed E. coli from the intestinal microbiota of three groups of healthy individuals, including preschool children, university students, and seniors of a longevity village, as well as colorectal cancer (CRC) patients, to probe the commensal E. coli populations for their diversity. We delineated the 2280 fresh E. coli isolates from 185 subjects into distinct genome types (genotypes) by PFGE. The genomic diversity of the sampled E. coli populations was so high that a given subject may have multiple genotypes of E. coli, with the general diversity within a host going up from preschool children through university students to seniors. Compared to the healthy subjects, the CRC patients had the lowest diversity level among their E. coli isolates. Notably, E. coli isolates from CRC patients could suppress the growth of E. coli bacteria isolated from healthy controls under nutrient-limited culture conditions. The coexistence of multiple E. coli lineages in a host may help create and maintain a microbial environment that is beneficial to the host. As such, the low diversity of E. coli bacteria may be associated with unhealthy microenvironment in the intestine and hence facilitate the pathogenesis of diseases such as CRC.

中文翻译：

---

大肠杆菌多样性：大肠癌低。

大肠杆菌主要是共生的，但也含有致病谱系。尚不清楚共生大肠埃希氏菌是否是致病谱系的潜在起源，可能是单基因种群还是多种群种群，对这些种群的阐明有望对大肠杆菌多样性与人类健康和疾病的关联产生新的见解。使用基因组测序和脉冲场凝胶电泳（PFGE）技术，我们分析了三组健康个体（包括学龄前儿童，大学生和长寿村的老年人）的肠道菌群中的大肠杆菌以及大肠癌（CRC） ）患者，以调查常见大肠杆菌种群的多样性。我们通过PFGE将来自185名受试者的2280株新鲜大肠杆菌分离物划定为不同的基因组类型（基因型）。采样的大肠杆菌种群的基因组多样性是如此之高，以至于给定的受试者可能具有多种基因型的大肠杆菌，宿主中的总体多样性从学龄前儿童到大学生再到高年级。与健康受试者相比，CRC患者在其大肠杆菌分离物中的多样性水平最低。值得注意的是，在营养有限的条件下，从CRC患者中分离出的大肠杆菌可以抑制从健康对照中分离出的大肠杆菌的生长。宿主中多种大肠杆菌谱系的共存可能有助于创建和维持对宿主有益的微生物环境。这样，大肠杆菌的低多样性可能与肠道中不健康的微环境有关，因此促进了诸如CRC等疾病的发病机理。