RESEARCH

Metal(loid) Biogeochemistry

Microorganisms contribute greatly to the biogeochemical cycling of metals and metalloids on Earth through transformational processes such as redox, complexation, and adsorptions.  These transformations contribute substantially to the availability of these nutrients and/or pollutants to organisms.  We take a laboratory- and field-based approach to examine biotic and abiotic transformation mechanisms, microbial communities and activities, biomineral formation, and resulting geochemistry that contributes to the overall health of natural and heavily polluted
environments. Current projects in the lab include fungi-induced selenium transformations, microbial manganese oxidation and biomineralization, and iron-sulfur-carbon cycling in riparian wetlands.

Project: Simultaneous transformation of manganese and selenium by fungi

Previous work by PI Santelli and others (1, 2, 3, 4 ) has shown that fungi are capable of making biominerals of brown manganese oxides by oxidizing manganese (II) dissolved in water.

Within the past few years, Santelli Lab alumna Carla Rosenfeld led a study looking at the potential for six fungi to reduce selenium from selenate or selenite, the phases that are mobile and bioavailable to organisms, to both solid and gas phases. The fungi make amorphous red nanoparticles of selenium that turn the biomass red! At first glance, these reduction-oxidation processes shouldn’t happen at the same time, but it turns out they can! A study led by Carla Rosenfeld, Mary Sabuda, and coauthors showed that the fungi can reduce Se and oxidize Mn simultaneously. This has really important implications for understanding current and ancient global biogeochemical cycles on Earth.

Read this 3-minute-read summary of the project, written by Mary Sabuda!

Ongoing project: Unraveling the genetic mechanisms behind fungal Se reactions using interdisciplinary transcriptomics and geochemical approaches

Mary Sabuda, Jackie Mejia, Katie Schroeder, and PI Cara Santelli are collaborating with the University of Minnesota Genomics Center and the Minnesota Supercomputing Institute on this NSF CAREER project.

Ongoing project: Fungal reduction of elevated selenate [Se(VI)] concentrations

Megan Wedal, Mary Sabuda, and Jackie Mejia conducted a study on the reduction of Se(VI) through time.

Ongoing project: Assessing the impact of organic carbon source and concentration on fungal selenium transformations

Mary Sabuda, Jackie Mejia, Megan Wedal, Brayden Kuester, and Cara Santelli are collaborating on this NSF CAREER project. Look out for results in the future!

Manoomin/Psin (Wild Rice)

KAWE GIDAA-NAANAAGADAWENDAAMIN MANOOMIN “First we must consider Manoomin / Psiη (Wild Rice)”

The Santelli lab is part of a highly interdisciplinary collaboration between Great Lakes Tribal communities and University of Minnesota researchers that prioritizes Tribal views in order to identify and tackle the threats faced by manoomin/psiη (wild rice) and its habitat and to further protect Indigenous resource sovereignty.  This project integrates the cultural significance, ecology, and policy of manoomin.

This project is funded by UMN Grand Challenges and the Institute on the Environment.

Learn more at the manoomin project website, Facebook page, or from this brief summary.

Bioremediation

Microorganisms play an integral role in transforming pollutants in the environment. These processes can be harnessed for cleaning up heavily impacted environments through passive techniques or advanced technologies. The Santelli lab conducts research on bioremediation of manganese in coal mine drainage as well as selenium bioremediation from industrial waste streams and mining processes.

Deep Subsurface Life

The continental crust is estimated to contain as much as 20% of Earth’s prokaryotic life. In these environments, microbes depend on the redox cycling of elements like Fe and S for energy, sourcing nutrients and substrates from the water and rock that make up their habitat. The project is based at the Soudan Underground Mine State Park, in northeastern Minnesota, a site that accesses a 2.7 Ga banded iron formation hosted half a mile underground. Our research investigates both the abiotic and biotic processes that contribute to biogeochemical cycling in these environments with special focus the cycles of carbon, sulfur, and iron. This project combines field sampling, metagenomics, and synchrotron-based geochemical analyses to better understand this isolated and unique environment.

Mineral-hosted Life

Minerals play several essential roles in deep subsurface environments. Their surfaces make up the primary habitat for microorganisms, with the vast majority of subsurface organisms expected to live within colonies attached to the surfaces of fractures in the crustal rock. Additionally, mineral-rock and mineral-microbe interactions are the source of essential elements, substrates, and nutrients for subsurface organisms, including ferric iron, carbon, and sulfur. We seek to better understand how minerals shape the biogeochemical landscape of the deep subsurface by characterizing the mineralogy of fracture surfaces, revealing the minerals available to microorganisms and the processes through which they are slowly changing, and organo-mineral complexes collected from Soudan Mine boreholes, to better understand the density and distribution of subsurface biofilms.

Microbial Ecology and Metagenomics

Many organisms in the deep subsurface are difficult or impossible to culture under laboratory conditions. Instead, we use bioinformatics to better understand how the extremophiles living below the Soudan Mine are able to survive the highly saline, low-energy conditions of the continental subsurface. To investigate the microbial community, we assemble metagenomes covering the entire microbial community using DNA from cells filtered from Soudan groundwaters. We can then reconstruct the genomes (as metagenome-assembled-genomes, or MAGs) of specific organisms to learn more about their metabolisms or probe the metabolic function of the subsurface community as a whole. These investigations include probing the cycling of organic sulfur, investigating whether these often-overlooked molecules could be an important source of energy to crustal organisms, and characterizing novel microbial Orders that haven’t been observed anywhere but Soudan.