Unique compositions, functions, and physiologies of root-associated fungi from a uranium mine in New Mexico

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Taylor A. Portman, Jennifer A. Rudgers, Abigail Granath and Soren Timura, Department of Biology, University of New Mexico, Albuquerque, NM, Jose M. Cerrato, Department of Civil, Construction and Environmental Engineering, University of New Mexico, Albuquerque, NM

Background/Question/Methods
Characterizing diverse root-associated fungi in mine wastes can accelerate the development of bioremediation strategies to stabilize heavy metals. Ascomycota fungi are well known for their mutualistic associations with plant roots and, separately, for accumulating and modifying toxic compounds from the environment, such as heavy metals. We documented fungal communities in plant roots on lands with a history of uranium (U) mining and compared against nearby reference sites. We also assessed the potential functional consequences of unique mining-associated fungal communities using plant bioassays and lab-based fungal physiological assays that manipulated growth temperature. We addressed (1) Do plants growing in mine sites have different root fungal communities than plants outside of mine sites? (2) Do soils from mine sites reduce plant growth relative to soils outside of mines? and (3) Do fungal isolates from mine sites have altered physiological growth responses to temperature? We sampled soils and cultured root-associated fungi from native blue grama grass (Bouteloua gracilis) from uranium mine sites and nearby off-mine sites in central New Mexico. We bioassayed soil function by growing blue grama in mine or off-mine soils in the greenhouse. Growth responses of fungal isolates were tracked for 14 days under temperature stress treatments to test the prediction that isolates from mine sites have greater stress resistance than isolates from off-mine sites.
Results/Conclusions
Roots from mine sites supported 20% lower fungal diversity than roots from off-mine sites, but did not differ in the abundance or overall community composition of culturable fungi or in levels of root colonization by fungal hyphae. However, a few fungal taxa were significantly more abundant in roots from mine than off-mine sites, notably Fusarium oxysporum and Darksidea sp.. Blue grama seeds grown in soils from mine sites were 48% less likely to emerge as seedlings, had 66% less biomass, and 20% greater mortality. Finally, fungal isolates that dominated mine sites had greater resistance to heat stress than isolates cultured from plants growing off-mine. Our results identified candidate, culturable root-associated Ascomycota taxa for bioremediation and increased understanding of the biological impacts of heavy metals on microbial communities and plant growth.