CSIRO Division of Animal, Food and Health Sciences, Werribee, Victoria, Australia.
PLoS One. 2012;7(7):e41615. doi: 10.1371/journal.pone.0041615. Epub 2012 Jul 30.
The genomic island encoding the locus of enterocyte effacement (LEE) is an important virulence factor of the human pathogenic Escherichia coli. LEE typically encodes a type III secretion system (T3SS) and secreted effectors capable of forming attaching and effacing lesions. Although prominent in the pathogenic E. coli such as serotype O157:H7, LEE has also been detected in Citrobacter rodentium, E. albertii, and although not confirmed, it is likely to also be in Shigella boydii. Previous phylogenetic analysis of LEE indicated the genomic island was evolving through stepwise acquisition of various components. This study describes a new LEE region from two strains of Salmonella enterica subspecies salamae serovar Sofia along with a phylogenetic analysis of LEE that provides new insights into the likely evolution of this genomic island. The Salmonella LEE contains 36 of the 41 genes typically observed in LEE within a genomic island of 49, 371 bp that encodes a total of 54 genes. A phylogenetic analysis was performed on the entire T3SS and four T3SS genes (escF, escJ, escN, and escV) to elucidate the genealogy of LEE. Phylogenetic analysis inferred that the previously known LEE islands are members of a single lineage distinct from the new Salmonella LEE lineage. The previously known lineage of LEE diverged between islands found in Citrobacter and those in Escherichia and Shigella. Although recombination and horizontal gene transfer are important factors in the genealogy of most genomic islands, the phylogeny of the T3SS of LEE can be interpreted with a bifurcating tree. It seems likely that the LEE island entered the Enterobacteriaceae through horizontal gene transfer as a single unit, rather than as separate subsections, which was then subjected to the forces of both mutational change and recombination.
肠上皮细胞脱落（LEE）编码岛是人类致病性大肠杆菌的重要毒力因子。LEE 通常编码一种 III 型分泌系统（T3SS）和分泌效应子，能够形成附着和消除病变。尽管在致病性大肠杆菌如 O157:H7 血清型中很突出，但 LEE 也已在柠檬酸杆菌、E. albertii 中检测到，尽管尚未得到证实，但它也可能存在于志贺氏菌属。以前对 LEE 的系统发育分析表明，基因组岛通过逐步获得各种成分而进化。本研究描述了来自沙门氏菌亚种 salamae 血清型 Sofia 的两个菌株的新 LEE 区域，以及对 LEE 的系统发育分析，为该基因组岛的可能进化提供了新的见解。沙门氏菌 LEE 包含 36 个通常在 LEE 中观察到的基因，位于一个 49,371bp 的基因组岛中，该基因组岛总共编码 54 个基因。对整个 T3SS 和四个 T3SS 基因（escF、escJ、escN 和 escV）进行了系统发育分析，以阐明 LEE 的系统发育。系统发育分析推断，以前已知的 LEE 岛是与新沙门氏菌 LEE 谱系不同的单一谱系的成员。以前已知的 LEE 谱系在柠檬酸杆菌和大肠杆菌和志贺氏菌中发现的岛之间分化。尽管重组和水平基因转移是大多数基因组岛系统发育的重要因素，但 LEE 的 T3SS 系统发育可以用二叉树来解释。LEE 岛似乎很可能作为一个整体通过水平基因转移进入肠杆菌科，而不是作为单独的小节，然后受到突变和重组的双重影响。
