Research
I am a plant and microbial scientist specialising in root-nodulating symbiotic interactions between (mainly) legumes and soil bacteria called rhizobia that “fix” atmospheric Nitrogen (N) gas into forms that the plant can use for its growth. These symbioses, in which the legume houses the rhizobia in structures on their roots called nodules, provide the host plant with all its N requirements, and thus allow these plants to colonize soils that are depleted in this most essential of plant nutrients. In addition to their ecological importance, many legumes, such as pea, beans, soybeans, clover etc., are of enormous agricultural significance, with their high-protein seeds being used for both human and animal consumption. Their ability to fix their own N means that no addition of N-containing fertiliser is required for their cultivation. This is an essential attribute for sustainable agriculture, not just economically, but also in terms of mitigation against pollution resulting from the massive overuse of agricultural fertilizer over the last 50 years. This overuse has resulted in the current “Nitrogen Crisis” in which waterways, groundwater, and even coastal ecosystems are polluted by harmful nitrates, and is also partly responsible for the enormous greenhouse gas (especially nitrous oxides) emissions that are produced by agriculture in the Global North. This can only be tackled by reducing our over-reliance on fertilisers; the efficient exploitation of N-fixing legumes is key to this endeavour, and my research is largely focused on this.
My expertise includes:
Nitrogen fixation by legume crops (pulses and forages): Currently measuring biological nitrogen fixation (BNF) by various legumes, such as field beans Vicia faba in an experimental rotation at the Centre for Sustainable Cropping(CSC) (Maluk et al. 2022), and soybean (Maluk et al. 2023). This work was/is funded by RESAS, and by various EU FP7 and Horizon2020 projects, such as Legume Futures and TRUE (https://cordis.europa.eu/project/id/727973/news)
Nitrogen fixation by non-legumes:Currently undertaking RESAS-funded work to assess the N-fixing microbiome of the C4 “energy grass”, Miscanthus, cropped on marginal land in Scotland without any inputs. This work will be presented at the 17th Symposium on Biological Nitrogen Fixation by Non-legumes in Naples, Italy, which I am co-organising (https://www.enfc2023.org/index.php/non-legumes).
Diversity of nodulated legumes and their microbial symbionts in native ecosystems in the UK and in the tropics:
Climate change also poses great threats to native Scottish legume biodiversity, which includes some of the rarest plants in the British Isles, the alpine milk vetches, Astragalus alpinus and Oxytropis species. Working with colleagues at the Royal Botanic Garden Edinburgh, we are helping to maintain Scotland’s natural capital by conducting research into the ecology of these N-fixing “Ice Age relic” plants which hang on precariously in their mountain habitats in the face of increasingly warmer winters.
Further afield, as part of the Gates-funded ENSA project, I am conducting fieldwork in the Brazilian Cerrado, Pantanal, and Amazon, and in the Ghanaian rainforest to investigate the evolution (and losses) of nodulation in tree legumes. This work has not only revealed to me the sheer diversity of legume symbioses, but also how fragile they and other components of these increasingly threatened ecosystems are. It’s only by cataloguing and describing this incredible diversity that we can convince the public and policy makers that it has intrinsic value, and that it must be preserved for future generations.
This research involves nodule sampling in the field, transmission electron microscopy (TEM), microbiome analysis, isolation of microsymbionts, sequencing of their genomes, and comparative genomics of both plant and bacterial partners in the symbiosis.
Plant transmission electron microscopy (TEM):the ultrastructure of beneficial plant-bacterial interactions, including crop legumes like faba bean. I also specialise in immunolocalisation of both conventionally (chemically)- and cryo-fixed plant material.
Current funders include:
EU H2020 Programme: https://root2res.eu/
Bill & Melinda Gates Foundation: ENSA project https://www.ensa.ac.uk/
More information and contacts:
Professor Euan James, James Hutton Institute – Botanics Stories (rbge.org.uk)
Euan JAMES | Research Leader in Beneficial Plant-Bacterial Interactions | PhD | James Hutton Institute, Aberdeen | Ecological Sciences Research | Research profile (researchgate.net)
?Euan James – ?Google Scholar
Past research
Identified the nature of the O2 regulation mechanism in legume nodules using electron microscopy.
Identified the mechanisms that allow flooding-tolerant legumes to fix N whilst flooded in both tropical and temperate ecosystems.
Confirmed the endophytic nature of several species of N-fixing bacteria in sugarcane and rice using light and electron microscopy.
Showed that a completely “new” (actually ancient) type of symbiont existed in legume nodules in tropical ecosystems that was unrelated to Rhizobium. These symbionts are now termed “Beta-rhizobia”.
