Department of Food Microbiology and Hygiene, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstrasse 28, 70599, Stuttgart, Germany.
Institute for Bioinformatics and Medical Informatics, University of Tübingen, Sand 14, 72076, Tübingen, Germany.
BMC Microbiol. 2019 Sep 5;19(1):212. doi: 10.1186/s12866-019-1578-4.
Several serious vegetable-associated outbreaks of enterohemorrhagic Escherichia coli (EHEC) infections have occurred during the last decades. In this context, vegetables have been suggested to function as secondary reservoirs for EHEC strains. Increased knowledge about the interaction of EHEC with plants including gene expression patterns in response to plant-derived compounds is required. In the current study, EHEC O157:H7 strain Sakai, EHEC O157:H strain 3072/96, and the EHEC/enteroaggregative E. coli (EAEC) hybrid O104:H4 strain C227-11φcu were grown in lamb's lettuce medium and in M9 minimal medium to study the differential transcriptional response of these strains to plant-derived compounds with RNA-Seq technology.
Many genes involved in carbohydrate degradation and peptide utilization were similarly upregulated in all three strains, suggesting that the lamb's lettuce medium provides sufficient nutrients for proliferation. In particular, the genes galET and rbsAC involved in galactose metabolism and D-ribose catabolism, respectively, were uniformly upregulated in the investigated strains. The most prominent differences in shared genome transcript levels were observed for genes involved in the expression of flagella. Transcripts of all three classes of the flagellar hierarchy were highly abundant in strain C227-11φcu. Strain Sakai expressed only genes encoding the basal flagellar structure. In addition, both strains showed increased motility in presence of lamb's lettuce extract. Moreover, strain 3072/96 showed increased transcription activity for genes encoding the type III secretion system (T3SS) including effectors, and was identified as a powerful biofilm-producer in M9 minimal medium.
The current study provides clear evidence that EHEC and EHEC/EAEC strains are able to adjust their gene expression patterns towards metabolization of plant-derived compounds, demonstrating that they may proliferate well in a plant-associated environment. Moreover, we propose that flagella and other surface structures play a fundamental role in the interaction of EHEC and EHEC/EAEC with plants.
在过去几十年中，发生了几起与食用蔬菜相关的严重肠出血性大肠杆菌（EHEC）感染暴发事件。在此背景下，蔬菜被认为是 EHEC 菌株的二次储存库。需要更多地了解 EHEC 与植物的相互作用，包括对植物衍生化合物的基因表达模式的反应。在当前的研究中，使用 RNA-Seq 技术研究了大肠杆菌 O157:H7 菌株 Sakai、大肠杆菌 O157:H 菌株 3072/96 和 EHEC/肠聚集性大肠杆菌（EAEC）混合菌株 O104:H4 菌株 C227-11φcu 在羔羊生菜培养基和 M9 最小培养基中的生长情况，以研究这些菌株对植物衍生化合物的差异转录反应。
许多参与碳水化合物降解和肽利用的基因在所有三种菌株中均上调，表明羔羊生菜培养基为增殖提供了足够的营养。特别是，分别参与半乳糖代谢和 D-核糖分解代谢的 galET 和 rbsAC 基因在研究的菌株中均上调。在共享基因组转录水平上最明显的差异是与鞭毛表达相关的基因。所有三种鞭毛层次结构的基因转录物在菌株 C227-11φcu 中高度丰富。Sakai 菌株仅表达编码基础鞭毛结构的基因。此外，两种菌株在存在羔羊生菜提取物时均表现出增加的运动性。此外，3072/96 株显示出编码 III 型分泌系统（T3SS）的基因转录活性增加，包括效应子，并且在 M9 最小培养基中被鉴定为强大的生物膜产生菌。
本研究提供了明确的证据，表明 EHEC 和 EHEC/EAEC 菌株能够调整其基因表达模式以代谢植物衍生的化合物，表明它们在植物相关环境中可能很好地增殖。此外，我们提出鞭毛和其他表面结构在 EHEC 和 EHEC/EAEC 与植物的相互作用中起着基本作用。
