Scientists uncover fungi's role in the cycle of life

Posted on 14 July 2010

The nitrogen cycle is the natural process that makes nitrogen available to all organisms on earth. Scientists at the University of York have discovered that one of the world’s most common and ecologically important groups of fungi plays an unsuspected role in this key natural cycle.

Almost all plants form symbiosis with fungi in their roots, know as mycorrhizas. The commonest type of mycorrhiza is called the arbuscular mycorrhiza (AM) and involves two-thirds of plant species. Unlike most fungi, the AM fungi get their supply of sugars for energy and growth from their plant partner and not from the decomposition of organic matter.

We have known for a long time that these fungi play a central role in the phosphorus cycle; now it seems that they are equally important in the nitrogen cycle

Dr Angela Hodge

Surprisingly, the researchers found that AM fungi thrive on decomposing organic matter and obtain large amounts of nitrogen from it. The fungus itself is much richer in N than plant roots, and calculations suggest that there is as much nitrogen in AM fungi globally as in roots.  Since fungal hyphae (the threads of which the fungus is composed) are much shorter-lived than roots, this finding has implications for the speed with which nitrogen cycles in ecosystems,  

The research, by Dr Angela Hodge and Professor Alastair Fitter in the Department of Biology at York was funded by the Biotechnology and Biological Sciences Research Council, is published in the latest issue of Proceedings of the National Academy of Sciences (PNAS).

Because these fungi cannot be grown in pure culture, the researchers created microcosms to isolate the fungi from plant roots and to allow them access to a patch of organic matter, and used stable isotopes to track the movement of nitrogen and carbon. Fungi that exploited decomposing organic matter were also better able to colonize a new plant. In addition, reducing the carbon supply to the fungus by shading the host plant did not diminish he fungal growth in the organic matter.

Dr Hodge said: "We have known for a long time that these fungi play a central role in the phosphorus cycle; now it seems that they are equally important in the nitrogen cycle, opening the possibility of exploiting them in the development of more sustainable forms of agriculture."

Notes to editors:

  • More about the University of York’s Department of Biology at www.york.ac.uk/depts/biol/
  • The paper Substantial nitrogen acquisition by arbuscular mycorrhizal fungi from organic material has implications for N cycling is published in the latest issue of the Procdeedings of the National Academy of Sciences.
  • BBSRC is the UK funding agency for research in the life sciences. Sponsored by Government, BBSRC annually invests around £470 million in a wide range of research that makes a significant contribution to the quality of life in the UK  and beyond and supports a number of important industrial stakeholders, including the agriculture, food, chemical, healthcare and pharmaceutical sectors.

    BBSRC provides institute strategic research grants to the following:

    The Babraham Institute, Institute for Animal Health, Institute of Biological, Environmental and Rural Studies (Aberystwyth University), Institute of Food Research, John Innes Centre, Rothamsted Research, The Genome Analysis Centre  and The Roslin Institute (University of Edinburgh). The Institutes conduct long-term, mission-oriented research using specialist facilities. They have strong interactions with industry, Government departments and other end-users of their research.

    For more information see: www.bbsrc.ac.uk


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