Endophytic bacteria: co-existence and chemical warfare

内生细菌（EB）生活在植物组织中，不会引起疾病的迹象。它们可能是水平或垂直传播的，可以被认为是在互惠菌和病原体之间的良性一端。据报道，EB在促进寄主植物生长和保护其免受害虫和病原体侵害方面具有益处。为了维持内生的生活方式，这些细菌必须与寄主植物和其他细菌和真菌内生菌相互作用，而不触发防御机制（合作），同时帮助植物识别和攻击病原体（化学战）。这些古老的关系不仅从进化的角度来看是迷人的，而且对于可持续作物生产和作为生物活性天然产品（包括抗菌剂和抗真菌剂）的新来源具有潜在的巨大价值。在过去，人们认为共生状态和发病机制很容易互换，很大程度上取决于环境条件。然而，来自基因组研究的证据并不支持这一点，因为共生体往往表现出减少的基因组，缺乏发病所需的必要成分。迄今为止，大多数数据来自动物共生体，因此分析EB以确定植物共生体是否也是如此是很重要的。如果这是真的，这将对这些生物在作物生产和保护中的应用产生重大影响，如生物肥料、生物农药、抗真菌剂等（用于粮食和工业作物），因为合作适应可能使它们比预期的更安全。此外，化合物可以被分离出来作为人类和动物健康的抗菌剂。近年来，从EB中分离出了许多新型抗生素，这表明EB仍然是一个相对未开发的资源，具有很高的发现新型生物活性的潜力。该项目将利用之前BBSRC iCASE项目BB/G017484/1“能源作物芒草中的细菌内生菌”中开发的IBERS的EB收集。基因组分析、诱变和植物筛选将为内生生活方式所需的适应提供洞见。同时，功能测试和随后的化学分离和表征将阐明由EB生产的生物活性化合物的商业应用，例如，作为作物生产/保护或抗菌产品。因此，该项目解决了一些BBSRC战略重点，包括：可持续地提高农业生产；食品、营养和健康；生物能源;以及对抗抗菌素耐药性。

Endophytic bacteria (EB) live within plant tissues without causing signs of disease. They may be horizontally or verticallytransmitted and can be considered to sit at the benign end of the spectrum between mutualists and pathogens. EB havebeen reported to confer benefits to the host plant in terms of growth promotion and protection from pests and pathogens. Inorder to maintain an endophytic lifestyle these bacteria must both interact with the host plant and other bacterial and fungalendophytes without triggering defence mechanisms (co-operation), yet assist the plant in identifying and attackingpathogens (chemical warfare). These ancient relationships are not only fascinating from an evolutionary perspective butare potentially of great value for both sustainable crop production and as novel sources of bioactive natural productsincluding antimicrobials and antifungals.In the past it was postulated that the states of symbiosis and pathogenesis were readily interchangeable, largely dependenton environmental conditions. However, evidence from genomic studies do not support this, as symbionts tend todemonstrate reduced genomes, lacking the necessary components required for pathogenesis. To date the majority of datais from animal symbionts, and so it is important to analyse EB to determine whether this is also the case for plantendosymbionts. If true, this has major implications for the application of these organisms in crop production and protection,as biofertilisers, biopesticides, antifungals etc. (for both food and industrial crops), as co-operative adaptation may renderthem inherently safer than predicted. Furthermore, chemical compounds may be isolated for application as antimicrobialsfor human and animal health. A number of novel antibiotics have been isolated from EB over recent years, indicating thatEB remain a relatively untapped resource with high potential for discovery of novel bioactives.This project will utilise the EB collection at IBERS developed in a previous BBSRC iCASE project BB/G017484/1 'Bacterialendophytes in the energy crop Miscanthus'. Genomic analysis, mutagenesis and in planta screening will provide insight intothe adaptations required for an endophytic lifestyle. Concurrently, functional testing and subsequent chemical isolation andcharacterisation will elucidate bioactive compounds produced by the EB for commercial application, e.g., as either cropproduction/protection, or antimicrobial products. This project therefore addresses a number of BBSRC strategic prioritiesincluding: Sustainably enhancing agricultural production; Food, nutrition and health; Bioenergy; and Combattingantimicrobial resistance.