‘The Daily Grind’: Tectonically driven oxidant production in the hot subsubsurface biosphere

Overview

Earth is a tectonically active planet, and subsurface faults and fractures provide habitats for microbial ecosystems in continental crust, ocean crust, and overlying ocean sediment. Importantly, the fracturing of silicate rocks along faults can split water via mechanochemical reactions (Kita et al., 1982and this hydrogen cab be used to support subsurface life (Hirose et al., 2011; Parkes et al., 2011; Telling et al., 2015). However, the ultimate fate of the equal equivalents of oxygen from the water splitting has remained enigmatic. Pilot experiments in our laboratory have shown that at temperatures 80°C) mechanochemical reactions to gain energy for growth?
3. What role could mechanochemical oxidant production have today in the microbial ecology of the tectonically active subsurface biosphere?
4. Could oxidant production from mechanochemical reactions have had a role in the early (pre-photosynthetic) evolution of life in hot subsurface fractures?

Methodology

i. Conduct laboratory experiments (both with and without microbial inocula) on a range of crushed natural minerals and rocks using a gastight planetary ball mill, pressure vessels, and microcosms. Changes in solutes and dissolved gases will be analyzed via ion chromatography, UV-vis spectrometry and gas chromatography/mass spectrometry, and changes in mineral surface radical speciation by electron spin paramagnetic resonance. Changes in microbial community will be assessed through comparisons of 16S rRNA diversity, metagenome analysis, and expression of mRNA.
ii. Collect natural environmental samples of hyperthermophilic microbial communities from hot springs in Iceland to use in above experiments,
iii. Use geochemical thermodynamic and kinetic modelling to model the mechanochemical reactions and calculate the potential energy generated to support life.
iv. Statistical analysis/synthesis. Relevant statistical methods (e.g. ANOVA, regression analysis, PCA analysis) will be used to assess the significance of results. Results will be synthesized with existing literature.

Project Timeline

Year 1

Literature review, pilot experiments, initial mineral experiments. Training in geochemical techniques and kinetic/thermodynamic modelling.

Year 2

Further experiments focused on assessing role of pressure on abiotic products of reactions. Training in kinetic and thermodynamic modelling. Training in microbiology techniques and bioinformatics. Fieldwork to collect Iceland hot spring samples. Attend UK conference. Prepare manuscript.

Year 3

Experiments assessing the potential of high temperature mechanochemical reactions to support microbial growth. Attend international conference. Prepare manuscript.

Year 3.5

Write up final thesis, prepare manuscript.

Training
& Skills

Newcastle University has a faculty-run postgraduate training programme that follows the Vitae Researcher Development Framework (http://www.vitae.ac.uk/). Each PhD student has a tailor-made Personal Development Plan, with the expectation of them taking 60 credits in the first year and 40 credits in the second year covering both specific skills required for the project (e.g. analytical methodology, statistical analysis) and transferable skills. The candidate will also gain expertise in the use of specialised experimental apparatus, geochemical analyses, molecular biology and bioinformatics, biogeochemical interpretation, and core research skills such as experimental design, fieldwork planning, data analysis and scientific writing.

References & further reading

Kita, I., Matsuo, S. & Wakita, H. H2 generation by reaction between H2O and crushed rock: an experimental study on H2 degassing from the active fault zone. Journal of Geophysical Research: Solid Earth 87, 10789-10795 (1982).
Hirose, T., Kawagucci, S. & Suzuki, K. Mechanoradical H2 generation during simulated faulting: Implications for an earthquake‐driven subsurface biosphere. Geophysical research letters 38 (2011).
Parkes, R. J. et al. Prokaryotes stimulate mineral H2 formation for the deep biosphere and subsequent thermogenic activity. Geology 39, 219-222 (2011).
Telling, J. et al. Rock comminution as a source of hydrogen for subglacial ecosystems. Nature Geoscience 8, 851-855 (2015).
Weiss, M.C. et al.The physiology and habitat of the last universal common ancestor Nature Microbiology volume 1, Article number: 16116 (2016).

Further Information

Please contact Dr. Jon Telling (jon.telling@newcastle.ac.uk) for further information

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