Identification and functional analysis of surface factors that enable human pathogens to adhere to and colonise plants.

食源性疾病是发达国家传染病的主要负担之一。病毒、细菌和寄生虫等微生物都与食物有关，其中许多可以在农场动物、作物植物和水中找到。然而，那些可以利用植物或动物作为宿主，即能够在宿主上或宿主内增殖的微生物与那些仅仅通过它们通过食物链运输的微生物之间有一个重要的区别。仅少数食源性病原体细菌（包括大肠杆菌O157和沙门氏菌）就占所有食源性疾病的很大比例，这主要是因为它们具有适应各种环境和在任何生物王国的宿主上增殖的非凡能力。这些病原体与动物宿主，特别是农场动物有密切联系。从这个来源，细菌可以通过苍蝇传播到水中，或传播到正在生长的作物上。虽然我们传统上将这些细菌与动物宿主联系在一起，但我们有充分的证据表明它们也可以在植物宿主上和内部增殖。这一点很重要，因为在过去二十年中，由受污染的新鲜农产品（以即食或最低限度加工的水果和蔬菜的形式）引起的食源性疫情数量有所增加。这种增加只能部分归因于更好的监测和检测方法，而且也有可能与气候变化有关。新鲜农产品的消费作为健康生活方式的一部分得到了正确的促进，这增加了充分了解食源性细菌在作物植物中定植的基础的需要。尽管我们对细菌-植物相互作用的生物学基础的认识还处于起步阶段，但对这一领域的认识正在上升。因此，重要的是建立一个坚实的基础，我们可以在此基础上做出明智的决定，影响食品安全实践和政府政策。该项目旨在确定一些关于食源性细菌如何定植作物的基本信息。可能有大量的基因参与其中，这些基因将归入不同的功能家族。该项目将重点研究细菌细胞表面结构的编码基因，即那些最有可能直接与植物细胞相互作用的基因。初步工作已经表明大肠杆菌O157:H7粘附因子在细菌-植物相互作用中的作用，将对其进行更详细的研究，以充分表征其作用。细菌细胞表面的结构很少孤立地起作用，当它们起作用时，它们受到极其严格的控制，以确保它们只在最合适的时间产生。因此，将鉴定出大肠杆菌O157:H7的其他表面因子，然后对其进行测试，以确定它们在细菌-植物相互作用中的作用。一部分细菌种群能够进入植物的内部组织，在那里它们无法被用于粮食生产的传统卫生技术所清除。是否有任何细菌表面因子在植物组织的细菌内化中起作用也将被评估。细菌与植物关系的另一方面也将被检查，以确定植物是否能够特异性地感知任何细菌表面因子。所使用的方法将为植物宿主和细菌之间关系的本质提供更清晰的画面。这些信息将有助于丰富知识，实现减少食源性疾病发生率的共同目标。

Foodborne illness is one of the main burdens of infectious disease in the developed world. Microbes such as viruses, bacteria and parasites are all associated with food and many of them can be found in farm animals, crop plants and water. However, there is an important distinction between those microbes that can use plants or animals as hosts, i.e. are able to proliferate on or within the host, and those that are simply transported through the food chain by them. Just a few bacteria that are foodborne pathogens (including E. coli O157 and Salmonella) account for a large proportion of all foodborne illness, largely because of their extraordinary ability to adapt to a wide range of environments and to proliferate on hosts of any biological kingdom. These pathogens have a strong association with animal hosts, in particular farm animals. From this source, the bacteria can be transmitted into water, by flies or onto growing crops. Although we traditionally associate these bacteria with animal hosts, we have good evidence to show that they can also proliferate on and within plant hosts. This is important because the number of foodborne outbreaks from contaminated fresh produce, in the form of ready-to-eat or minimally processed fruit and vegetables has increased over the past two decades. The increase can only be partly accounted for by better surveillance and detection methods, and there is a possibility that it is also linked to climatic change. Consumption of fresh produce is rightly promoted as part of a healthy life-style, which increases the need to fully understand the basis of colonisation of crop plants by foodborne bacteria. Appreciation of this area is on the rise, although our knowledge of the biological basis to bacteria-plant interactions is in its infancy. Therefore, it is important to build up a solid foundation from which we can make informed decisions that affect food safety practices and government policy. This project aims to determine some of the basic information about how foodborne bacteria colonise crop plants. There are likely to be a large number of genes involved which will fall into different functional families. This project will focus on the genes that encode structures present on the bacterial cell surface, i.e. those most likely to interact directly with plant cells. Preliminary work has already indicated a role for an E. coli O157:H7 adherence factor in bacteria-plant interactions and it will be investigated in much greater detail to fully characterise its role. Structures on the bacteria cell surface seldom work in isolation and when they do, they are extremely tightly controlled to ensure that they are only produced at the most appropriate time. Therefore, additional surface factors of E. coli O157:H7 will be identified, which can then be tested to determine their role in the bacteria-plant interactions. A proportion of the bacterial population are able to enter the internal tissues of plants, where they cannot be removed by conventional sanitation techniques used in food production. Whether any of the bacterial surface factors play a role in bacterial internalisation of plant tissue will also be assessed. The other side of the bacteria-plant relationship will also be examined, to determine whether the plant can sense any of the bacterial surface factors specifically. The approaches used will provide a clearer picture as to the nature of the relationship between plants host and bacteria. The information will contribute to a wider wealth of knowledge, with a common goal to reduce the incidence of foodborne illness.