Streptomyces bacteria: Antibiotic production in the wheat endosphere

链霉菌：小麦内圈的抗生素生产

• 批准号: BB/T015446/1
• 负责人: Matthew Hutchings
• 金额: $ 64.04万
• 依托单位: John Innes Centre
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=BB%2FT015446%2F1
• 关键词: Streptomyces; bacteria; Antibiotic; production; wheat

Plants use photosynthesis to fix carbon dioxide from the air into glucose which they use as food. However, up to 40% of the carbon they fix is released into the soil from their roots and this appears to be a mechanism to attract beneficial bacteria from the surrounding soil. The bacteria use the root exudates as food and this helps the plants assemble a healthy microbiome. Some of these microbes protect the plants against disease and others help them get important nutrients from the soil. The root microbiome is therefore essential for plant health, but crop breeding over hundreds of years has selected traits such as bigger plants with more grain while perhaps neglecting the (unknown) effects on the microbiome. There is now growing interest in manipulating the microbiomes of crop plants such as wheat to make them more resistant to disease and to abiotic stresses like drought and salinity. Wheat is a staple crop for about 4 billion people and one of the most important crops in the world so increasing yields is essential if we are to support a growing world population. Our project focuses on a genus of soil bacteria called Streptomyces. The ~600 known species of Streptomyces make numerous secondary metabolites, and these account for half of all the known antibiotics. They are easy to isolate from soil but also form stable interactions with plant roots and can colonise the rhizosphere and endosphere of a wide range of different plants. We have found they are abundant inside wheat roots and that some strains can protect wheat against fungal diseases such as Take-all which can cause devastating crop losses. For one of these strains we have identified the molecules and genes responsible for this antifungal activity and shown it is increased two-fold when we add indole 3 acetic acid, a plant hormone present in wheat root exudates, to the growth medium. In this proposal we aim to look in more detail at the colonisation of wheat roots by soil dwelling, antibiotic-producing Streptomyces bacteria. We will sequence the genomes of 10 strains we have isolated from wheat plants which inhibit the take-all fungus on agar plates, identify the antifungals made by these strains and determine if they can protect wheat plants against take-all disease. We will also try to discover which molecules in wheat root exudates can feed these bacteria and switch on their production of secondary metabolites. Since Streptomyces bacteria form spores which can be dried and stored for long periods, we are interested in developing wheat seed coatings containing these spores so the bacteria grow into the roots of germinating wheat plants and protect them against disease. We will also test the role of the type VII secretion system in root colonisation by these strains since we have preliminary evidence that this system helps them outcompete other bacteria for wheat root colonisation. Our ultimate aim is to develop streptomycetes as seed coatings to protect wheat plants against fungal disease and to discover molecules from wheat root exudates that we can use to switch on secondary metabolite production in vitro because we know that 90% of the secondary metabolites they encode are not made under laboratory conditions. This could help us discover new and useful molecules from these bacteria.

植物利用光合作用将空气中的二氧化碳固定为它们用作食物的葡萄糖。然而，它们固定的高达40%的碳从它们的根部释放到土壤中，这似乎是一种从周围土壤中吸引有益细菌的机制。细菌利用根分泌物作为食物，这有助于植物组装健康的微生物群。其中一些微生物保护植物免受疾病侵袭，另一些微生物帮助植物从土壤中获得重要的养分。因此，根部微生物群对植物健康至关重要，但数百年来的作物育种选择了一些特征，如更大的植物具有更多的谷物，而可能忽略了对微生物群的(未知)影响。现在，人们越来越有兴趣操纵小麦等作物的微生物群，使它们更能抵抗疾病和干旱、盐碱等非生物胁迫。小麦是约40亿人的主要农作物，也是世界上最重要的作物之一，因此，如果我们要养活不断增长的世界人口，提高产量是至关重要的。我们的项目专注于一种名为链霉菌的土壤细菌属。已知的约600种链霉菌能产生大量的次生代谢产物，这些次生代谢产物占所有已知抗生素的一半。它们很容易从土壤中分离出来，但也能与植物根形成稳定的相互作用，并能在各种不同植物的根际和内圈定居。我们发现，它们在小麦根中含量丰富，一些菌株可以保护小麦免受全蚀病等真菌疾病的侵袭，这些疾病可能导致毁灭性的作物损失。对于其中一个菌株，我们已经确定了负责这种抗真菌活性的分子和基因，并表明当我们在生长介质中添加吲哚3乙酸时，这种抗真菌活性增加了两倍。吲哚3乙酸是一种存在于小麦根分泌物中的植物激素。在这项提案中，我们的目标是更详细地研究土壤中栖息的、产生抗生素的链霉菌对小麦根的定植。我们将对从小麦植株中分离出的10个抑制琼脂平板上全蚀病菌的菌株的基因组进行测序，鉴定这些菌株制造的抗真菌药物，并确定它们是否可以保护小麦植株免受全蚀病的侵染。我们还将试图发现小麦根分泌物中的哪些分子可以喂养这些细菌，并开启它们产生次生代谢物的过程。由于链霉菌形成的孢子可以干燥并长期储存，我们有兴趣开发包含这些孢子的小麦种衣剂，以便细菌生长到萌发的小麦植株的根中，并保护它们免受疾病的侵袭。我们还将测试VII型分泌系统在这些菌株根部定植中的作用，因为我们有初步证据表明，这个系统帮助它们在小麦根部定植方面胜过其他细菌。我们的最终目标是开发链霉菌作为种衣剂来保护小麦免受真菌疾病的侵染，并从小麦根分泌物中发现可以用来在体外启动次生代谢物产生的分子，因为我们知道它们编码的90%的次生代谢物不是在实验室条件下产生的。这可以帮助我们从这些细菌中发现新的有用的分子。