Biogeochemical cycle of tungsten
in modern and ancient Earth’s surface environments
Background information
Funded by the New Frontiers in Research Fund (NFRF) grant with international collaborations with scientists from Earth sciences, chemistry, biology, engineering and philosophy, I am currently investigating tungsten (W) as a potential biosignature on Earth and other planetary bodies. Recent findings have offered evidence that W-dependent biochemical pathways (as a W co-factor; co-factors are metals that is associated to enyzmes and proteins to catalyze a reaction in a cell) likely preceded molybdenum (Mo)-dependent biochemical pathways (a Mo co-factor) due to changes in the Earth’s surface oxidation state from the Archean (4.0 to ~2.5 billion years ago) to the early-Proterozoic (<~2.5 billion years ago). This change in the availability of W and Mo in ancient seawater before and after the Great Oxidation Event (GOE), the first rise in atmospheric oxygen, may have induced changes in biochemical pathways through different enzymes and proteins within ancient marine microbes, altering metal co-factors.
What am I working on?
To test whether W isotopes can serve as a biosignature, I am currently working on the following projects:
Determining the biological fractionation of W isotopes by W-utilizing bacteria and archaea;
Identifying W-associated enzymes and proteins in extremophiles using a cutting-edge metalloproteomics approach;
Conducting single-phase experiments with a variety of iron minerals and W to constrain the abiotic uptake of W and isotopic fractionation across different solution conditions;
Building a database of W isotopic compositions from geologic materials, including modern hot springs and Precambrian rocks.
In the future, the findings from this research may be applied to sample-return missions, which are currently being proposed for missions over the coming decades.
Using innovative ways to simplify experimental design
Growing anaerobic thermophiles can be very challenging and cumbersome. To reduce the need for subsampling with nitrogen-purged needles under a sterile field, I decided to take an alternative approach by using Hungate tubes and serum bottles to directly measure growth curves while maintaining anaerobic conditions. With the help of a 3D printer and a team of collaborators from Carleton University and the University of Colorado Boulder, we managed to make this idea a reality.
Project 1: Instead of purchasing $600 parts, we 3D printed a part for the Thermo Scientific™ GENESYS™ 30 Visible Spectrophotometer to allow direct measurement of cell density using Hugate tubes and serum bottles (working with Dr. Geoff Pignotta).
Project 2: Some microbes are much more challenging to grow and require continuous monitoring. In addition to these challenges, I am currently working with Pyrococcus furiosus, which grows optimally at 90 °C. Because its growth rate can vary, sometimes fast, sometimes slow, continuous, non-invasive measurements help minimize contamination risks and allow the researcher to get some sleep while the culture is running. Together with the team at CU Boulder, we are currently testing a micro-logger, a device that continuously measures cell density at 620 nm (working with the Kopf lab).
Tungsten: a critical mineral resource
Additional project
Tungsten has been recognized as a critical mineral by Canada, the United States, and the European Union due to significant supply vulnerabilities arising from its concentrated production in China and Russia. Known for having highest melting point, high density, high tensile strength and very resistent to wear, tear and corrosion, tungsten is often used in aeronautical engineering, defense systems, and advanced drilling technologies. Its importance is further increasing as it becomes integral to emerging renewable energy technologies. Together, these geopolitical and technological drivers have heightened global attention on this strategically important metal. Thus, understanding its biogeochemical cycling is therefore also essential for informing future resource recovery strategies.