Xuefeng Peng, Ph.D.

Postdoctoral Scholar, Earth Science, University of California, Santa Barbara

Project: Impact of Marine Fungi on Global Biogeochemical Cycling of C and N

My research as a Simons Postdoctoral Fellow aims at elucidating the potentially significant role marine fungi play in the global biogeochemical cycling of carbon (C) and nitrogen (N). Compared to their terrestrial counterparts, marine fungi are vastly understudied partly because of their cell biology and feeding strategies. As osmotrophs, fungi feed by secreting extracellular enzymes into the environment to depolymerize food substrates before transporting the digested monomers and nutrients back into the cell for growth. Such a lifestyle has largely defined fungi primarily as biomass degraders, and hence they should play an important role in remineralization in global biogeochemical cycles.

Recent evidence has suggested that fungi in marine sediments could be responsible for a significant portion of nitrate removal and the production of nitrous oxide (N2O, a potent greenhouse gas). Moreover, fungi’s ability to degrade large particles in the water column, along with their spore-forming life cycles, provides them a special position in the microbial food web, which remineralizes organic matter in the mixed layer and reduces particle export. However, most of our knowledge describing marine fungi’s ecological and geochemical roles remains qualitative. Little is known about the marine fungi’s activity and their quantitative contribution to geochemical cycles of C and N.

We propose to determine the fungal activity in organic matter degradation and N2O production in coastal and estuarine sediments, coastal seawater and an open ocean oxygen minimum zone. Incubation experiments targeting fungal populations will be performed to quantify their contribution to C and N turnover in marine sediments and water columns. We aim to link fungal abundance and diversity to their activities using next-generation sequencing, which will employ a novel method I developed that effectively extracts fungal DNA and RNA from complex microbial communities and environments. Additionally, we will isolate novel marine fungal strain responsible for C and N turnover.

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