In this section I provide highlights and a behind-the-paper perspective of selected articles. For a full record of my publications, see my Google Scholar Profile.
In the Spotlight.
The trace metal tungsten is rare in extant organisms. With similar physical properties, molybdenum is the preferred metal in enzymes serving diverse functions. In this paper, we describe a thermophile that obligately uses tungsten and not molybdenum.
Highlights:
We achieved stable growth of Caldarchaeales/Aigarchaeota in a mixed anaerobic culture supplemented with tungsten.
We identified six different tungsten-dependent oxidoreductases in metagenome-assembled genomes.
Our FISH-nanoSIMS approach revealed xylose as the preferred organic substrate of those substrates tested.
We showed that tungsten dependence is widespread among this lineage comprising four genera and 11 species. These live in globally distributed hydrothermal systems, including Great Boiling Springs, Yellowstone, Tengchong (China), Taupo (New Zealand), and the Lau basin in the Southern Pacific.
Tungsten-dependent oxidoreductases have been essential for the evolution of this lineage due to gene family expansions and multiple lateral gene transfers.
Open access!
The production potential of methane is widely unknown for remote peatlands located in the Western Amazon. We characterized geochemical gradients, including methane abundances, in soil profiles. We found that oxides of nitrogen, such as nitrite or nitrous oxide, critically affect the activity of soil methanogens, which may impact the overall methane flux.
Highlights:
We identified communities of diverse and novel methanogens individual to the geochemically different peat soils.
Ammonia-oxidizing archaea were highly abundant in acidic, oligotrophic peats, likely driving nitrification to produce nitrite.
In incubation experiments, we demonstrate an 85% reduction of methanogenesis by nitrite and complete inhibition by nitrous oxide.
Open access!
Behind the paper:
The Amazon basin contains large amounts of organic carbon in unexplored peatlands. I went to these places and probed their microbiology and geochemistry.
I measured gas emissions using static lids placed on top of the soil. To retrieve vertical profiles of peat layers, I used a 1 m long corer (note the visual gradient of decomposing soil from the top at the right to the bottom). This is hard physical work, especially in a tropical climate!
Undergraduate researchers Kaitlyn Tylor and Zac Zamora working on soil slurries in the oxygen-free glovebox. We use this tool often to study oxygen-sensitive processes, such as microbial methanogenesis. Soil slurries are then additionally treated outside to test activity under different conditions.
