This work could have sweeping implications for studies of biogeochemistry, since certain ecosystems, especially those in the tundra, are dominated by lichens. Ecosystem-wide nitrogen fixation rates are often inferred based on the acetylene-reduction assay (ARA). To interpret the results of this assay, a conversion factor based on the standard molybdenum-dependent system is typically used. However, if a substantial portion of the nitrogen fixation is taking place via alternative means, the standard conversion factor could produce wildly inaccurate interpretations. Even if one is willing to consider that a different conversion factor should be used, determining the proper conversion factor may become especially problematic since the proportion of standard to alternative nitrogen fixation could vary greatly based on the season or micro-environment. Therefore, a greater understanding of vanadium, molybdenum, and nitrogen dynamics may be needed before we can continue to rely blindly upon the commonly-used ARA for ecosystem-wide studies.
|Peltigera rufescens, a lichen with a cyanobacterial photobiont from the genus Nostoc, in the Alaskan tundra.|
Hodkinson, B. P., J. L. Allen, L. L. Forrest, B. Goffinet, E. Sérusiaux, Ó. S. Andrésson, V. Miao, J.-P. Bellenger, and F. Lutzoni. 2014. Lichen-symbiotic cyanobacteria associated with Peltigera have an alternative vanadium-dependent nitrogen fixation system. European Journal of Phycology 49(1): 11-19.
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[This work was supported in part by the National Science Foundation under grants OCI-1053575 and DEB-0919284.]