Department of Food Microbiology, Institute of Food Science and Biotechnology, University of Hohenheim, 70599 Stuttgart, Germany.
Appl Environ Microbiol. 2011 Dec;77(24):8705-13. doi: 10.1128/AEM.06492-11. Epub 2011 Oct 14.
In this study, we characterized the genetic background of various nleA variants in 106 Shiga toxin-producing Escherichia coli (STEC) and enteropathogenic Escherichia coli (EPEC) strains. The flanking regions of eight nleA variants were analyzed by DNA sequencing and compared with the corresponding regions of five previously described NleA-encoding prophages. The analyzed nleA variants were all located downstream of the DNA region responsible for phage morphogenesis. In particular, the type III effector genes avrA, ospB, nleH, and nleG and IS elements were detected in the neighborhood of nleA. The structure of the eight analyzed regions flanking nleA primarily resembled the corresponding region of the NleA₄₇₉₅-encoding prophage BP-4795. Using PCR, the gene order flanking 13 nleA variants in strains of different serogroups was compared to the respective regions in reference strains. The analyses showed that strains which harbor prophages with conserved flanking regions of a particular nleA variant predominantly occurred, and IS elements were additionally detected in these regions. We were able to mobilize nleA by transduction in 20% of strains determined, which comprised in particular EPEC strains harboring an nleA variant, the gene encoding the protein known as "EspI-like." Plaque hybridization was used to identify phages that harbor the genes stx and nleA. However, only two strains harbored variant nleA₄₇₉₅ in the genome of an Stx1 prophage.
在这项研究中，我们对 106 株产志贺毒素大肠杆菌（STEC）和肠致病性大肠杆菌（EPEC）中的各种 nleA 变体的遗传背景进行了描述。通过 DNA 测序分析了 8 种 nleA 变体的侧翼区域，并与之前描述的 5 种 NleA 编码噬菌体的相应区域进行了比较。分析的 nleA 变体均位于负责噬菌体形态发生的 DNA 区域的下游。特别是，avrA、ospB、nleH 和 nleG 型 III 效应基因和 IS 元件在 nleA 的附近被检测到。nleA 侧翼的 8 个分析区域的结构主要类似于 NleA₄₇₉₅ 编码噬菌体 BP-4795 的相应区域。通过 PCR，比较了不同血清群菌株中 nleA 侧翼的 13 个变体的基因顺序与参考菌株的相应区域。分析表明，主要存在携带特定 nleA 变体的噬菌体具有保守侧翼区域的菌株，并且在这些区域还检测到了 IS 元件。我们能够通过转导在 20%的确定菌株中动员 nleA，这些菌株主要包括携带 nleA 变体的 EPEC 菌株，该基因编码称为“EspI-like”的蛋白质。噬菌斑杂交用于鉴定携带 stx 和 nleA 基因的噬菌体。然而，只有两株 Stx1 噬菌体基因组中携带变异 nleA₄₇₉₅。
