Image courtesy of Nuccio, E.E., et al. “An arbuscular mycorrhizal fungus significantly modifies the soil bacterial community and nitrogen cycling during litter decomposition.” Environ. Microbiol. 15(6), 1870–1881 (2013)
Hyphae (branching, filamentous fungal structures) grow in decomposing litter as part of a study examining how arbuscular mycorrhizal fungi interact with soil microbial communities.
Arbuscular mycorrhizal (AM) fungi form intimate affiliations with the roots of many types of plants. This classic example of symbiosis is commonly understood to involve AM fungi helping plants take up nutrients from soil and receiving in exchange some of the sugars generated by the plants from photosynthesis. Although AM fungi play a large role in carbon and nitrogen cycling in terrestrial environments, details of how they actually function and affect soil microbes remain poorly understood.
These findings reveal an additional layer of complexity in this symbiotic system and yield another important puzzle piece toward understanding the complex routes by which carbon and nitrogen flow through ecosystems.
The impact of AM fungi on the community of soil microbes has not been examined in detail due to the difficulty of tracking nanoscale processes in complex soil habitats. A team of Department of Energy researchers at the University of California, Berkeley and Lawrence Livermore National Laboratory have now used a combination of “omics” tools and nanoscale tracking of isotopically labeled compounds to dissect interactions of AM fungi and soil microbial communities in carefully constructed soil microcosms. Plant-affiliated AM fungi were allowed to colonize small chambers containing soil samples and radiolabelled dead plant material (“litter”). The team found that the AM fungi significantly affected the composition of the surrounding microbial community by increasing the abundance of microbes involved in plant litter degradation. During this degradation, soil microbes played an important role in liberating nitrogen compounds bound in dead plant matter. The team observed significant uptake of microbially released nitrogen (but not carbon) by the AM fungi.
Mary K. Firestone
University of California, Berkeley,
130 Mulford Hall, Berkeley, CA 94720
This work was funded by the DOE Office of Science Biological and Environmental Research program (DOE Genomic Science Program grant FOA DE-PS02-09ER09-25), an Underwood Fellowship (BBSRC) and California Experiment Station project 6117-H, a BBSRC research grant BB/E016359/1, LLNL LDRD 10-ERD-021, and a UC Laboratory Research Fees grant 116577.
Nuccio, E.E., et al. “An arbuscular mycorrhizal fungus significantly modifies the soil bacterial community and nitrogen cycling during litter decomposition.” Environ. Microbiol. 15(6), 1870–1881 (2013). [DOI: 10.1111/1462-2920.12081].
University, DOE Laboratory