"Adaptation of Frankia, alders, and their symbiosis to environmental stress. Adaptation au stress environnemental de Frankia, des aulnes et de leur symbiose."

弗兰克氏菌属的丝状放线菌普遍存在，并在全球固氮中发挥着重要作用。它们与寄主植物(放线菌植物，其中包括赤杨)建立了类似于带有根瘤菌的豆类植物的根瘤共生关系。在北美，赤杨因其分布、坚固性和对各种恶劣环境条件的适应性而特别令人感兴趣。尽管放线赤杨通常用于荒地的植被重建，但很少有研究集中于自然和人为胁迫(土壤养分缺乏、重金属)如何影响放线木共生。考虑到在腐生的生命周期中，鹿茸直接暴露在这些胁迫下，这些问题更加重要。具体地说，我将研究：1-生长中的Frankia spp.2--被金属污染的土壤中的赤杨、乳木和外生菌根共生体之间的相互作用的研究，以及3--根瘤中的细菌种群。我的研究计划主要集中在阐明放线菌和弗兰克氏菌是如何。适应环境压力(自然的和人为的)。通过这些知识，我们能够了解人类活动对这些生物的影响，这些生物在加拿大无处不在，并根据赤杨树种和Frankia菌株组合的自然潜力量身定做根降解或植物提取技术。必须强调的是，对Frankia共生(放线菌共生)的研究相对较少。这与它们在自然界中的重要性形成了鲜明对比；据估计，全球15%至25%的固氮可归因于这些微生物。不幸的是，对鹿茸及其共生关系的研究构成了一些技术困难。我正在系统地使用最先进的技术来解决这些困难，并以综合的方式进行这项重要的研究。这导致了对高能力学生的培训，以及工业合作伙伴的参与，以造福于科学和社会。

Filamentous actinobacteria of the genus Frankia are ubiquitous and participate significantly in global nitrogen fixation. With their host plants (actinorhizal plants, amongst which alders), they establish a root nodule symbiosis analogous to that of legumes with rhizobia. In North America, alders are of particular interest for their distribution, robustness and adaptation to a wide range of harsh environmental conditions. Although actinorhizal alders are routinely used for the revegetation of derelict lands, little research has focussed on how natural and anthropogenic stress (soil nutrient deficiency, heavy metals) affect the alder actinorhizal symbiosis. These questions are even more important considering that frankiae, in their saprophytic life cycle, are directly exposed to these stresses. Specifically, I will study: 1- cellular differentiation of growing Frankia spp. populations (i.e. massive conversion to difformed hyphae), 2- the study of interactions between alder, frankiae and ectomycorrhizal symbionts in soils that are contaminated with metals, and 3- the bacterial populations in root nodules. My research program focusses mainly on elucidating how actinorhizal alders and Frankia sp. adapt to environmental stress (both natural and anthropogenic). Through this knowledge, we are able to understand the impact of human activity on these organisms which are ubiquitous in Canada, and tailor rhizodegradation or phytoextraction technologies according to the natural potential of combinations of alder species and Frankia strains. It must be emphasized that the Frankia symbiosis (actinorhizal symbiosis) is relatively understudied. This contrasts with their importance in Nature; it is estimated that 15% to 25% of global nitrogen fixation can be attributed to these organisms. Unfortunately, the study of frankiae and their symbiosis to comprise a number of technical difficulties. I am addressing these difficulties using state-of-the-art techniques, in a systematic fashion, and pursuing this important research in an integrated manner. This results in the training of highly competent students, and in the involvement of industrial partners for the benefit of science and society.