Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA.
Food Microbiol. 2013 Sep;35(2):136-42. doi: 10.1016/j.fm.2013.03.002. Epub 2013 Mar 19.
Lettuce and spinach are increasingly implicated in foodborne illness outbreaks due to contamination by Escherichia coli O157:H7. While this bacterium has been shown to colonize and survive on lettuce leaf surfaces, little is known about its interaction with the roots of growing lettuce plants. In these studies, a microarray analyses, mutant construction and confocal microscopy were used to gain an understanding of structure and function of bacterial genes involved in the colonization and growth of E. coli O157:H7 on lettuce roots. After three days of interaction with lettuce roots, 94 and 109 E. coli O157:H7 genes were significantly up- and down-regulated at least 1.5 fold, respectively. While genes involved in biofilm modulation (ycfR and ybiM) were significantly up-regulated, 40 of 109 (37%) of genes involved in protein synthesis were significantly repressed. E. coli O157:H7 was 2 logs less efficient in lettuce root colonization than was E. coli K12. We also unambiguously showed that a ΔycfR mutant of E. coli O157:H7 was unable to attach to or colonize lettuce roots. Taken together these results indicate that bacterial genes involved in attachment and biofilm formation are likely important for contamination of lettuce plants with Shiga toxin-producing E. coli strains.
生菜和菠菜由于受到大肠杆菌 O157:H7 的污染，越来越多地引发食源性疾病爆发。尽管这种细菌已被证明会在生菜叶片表面定植和存活，但对于其与生长中的生菜根系的相互作用却知之甚少。在这些研究中，使用了微阵列分析、突变体构建和共聚焦显微镜技术，以了解参与大肠杆菌 O157:H7 在生菜根系上定植和生长的细菌基因的结构和功能。与生菜根系相互作用三天后，大肠杆菌 O157:H7 的 94 个和 109 个基因分别至少上调和下调 1.5 倍。虽然与生物膜调节（ycfR 和 ybiM）相关的基因明显上调，但参与蛋白质合成的 109 个基因中有 40 个（37%）明显受到抑制。大肠杆菌 O157:H7 在生菜根系上的定植效率比大肠杆菌 K12 低 2 个对数级。我们还明确表明，大肠杆菌 O157:H7 的 ΔycfR 突变体无法附着或定植生菜根系。这些结果表明，参与附着和生物膜形成的细菌基因可能对产志贺毒素大肠杆菌菌株污染生菜植物很重要。
