Escherichia coli   is a very versatile species for which diversity has been explored from various perspectives highlighting, for example, phylogenetic groupings and pathovars, as well as a wide range of O serotypes. The highly variable O-antigen, the most external part of the lipopolysaccharide (LPS) component of the outer membrane of   E. coli  , is linked to the innermost lipid A through the core region of LPS of which five different structures, denominated K-12, R1, R2, R3 and R4, have been characterized so far. The aim of the present study was to analyse the prevalence of these LPS core types in the   E. coli   species and explore their distribution in the different   E. coli   phylogenetic groups and in relationship with the virulence gene repertoire. Results indicated an uneven distribution of core types between the different phylogroups, with phylogroup A strains being the most diverse in terms of LPS core types, while phylogroups B1, D and E strains were dominated by the R3 type, and phylogroups B2 and C strains were dominated by the R1 type. Strains carrying the LEE virulence operon were mostly of the R3 type whatever the phylogroup while, within phylogroup B2, strains carrying a K-12 core all belonged to the complex STc131, one of the major clones of extraintestinal pathogenic   E. coli   (ExPEC) strains. The origin of this uneven distribution is discussed but remains to be fully explained, as well as the consequences of carrying a specific core type on the wider aspects of bacterial phenotype.

中文翻译：

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大肠杆菌物种中脂多糖核心类型的多样性与系统发育相关，毒力基因库和 VI 型分泌系统的分布

  大肠杆菌  是一种用途非常广泛的物种，已从各种角度探索了其多样性，例如系统发育分组和致病菌，以及广泛的 O 血清型。 高度可变的 O 抗原，即大肠杆菌 外膜脂多糖 (LPS) 成分的最外部部分，通过 LPS 的核心区域与最内层的脂质 A 相连，LPS 的核心区域有五个不同的结构，称为 K-12 , R1, R2, R3 和 R4, 到目前为止已被表征。本研究的目的是分析这些 LPS 核心类型在 大肠杆菌 物种中的流行情况，并探索它们在不同 大肠杆菌中 的分布。      系统发育组和与毒力基因库的关系。结果表明，不同种系间核心类型分布不均，其中种系A菌株的LPS核心类型最为多样化，而种系B1、D和E菌株以R3型为主，种系B2和C菌株为以R1型为主。携带 LEE 毒力操纵子的菌株大多属于 R3 型，无论系统发育群如何，而在系统发育群 B2 中，携带 K-12 核心的菌株都属于复合体 STc131，这是肠外致病性 大肠杆菌 的主要克隆之一  (ExPEC) 菌株。讨论了这种不均匀分布的起源，但仍有待充分解释，以及携带特定核心类型对细菌表型更广泛方面的影响。