Hydrogenases are enzymes that catalyze the reversible reaction H2 <-> 2H+ + 2e-. They are widespread throughout phylogenetically distinct microorganisms and currently three types of hydrogenases are known: [NiFe]-, [FeFe]- and [Fe]-hydrogenases.
In hydrothermal vent environments, hydrogen is emitted with the hydrothermal fluids and can reach several millimolar. Due to seawater-endmember fluid mixing processes, steep thermal and chemical gradients can persist providing both electron donors and acceptors. Microbially mediated hydrogen oxidation generates energy (in form of ATP), which can drive local biomass synthesis.
In porewater sediments (where hydrogen levels are commonly in the nanomolar range) hydrogen has a direct impact on carbon degradation because it is expected to affect fermentation and hydrogen-based terminal metabolisms.
An activity-based screen was developed within our group to detect hydrogenase enzymes from hydrothermal vent metagenomes. This activity-based screen uses a broad-host range fosmid vector and a hydrogenase mutant (Shewanella oneidensis DhyaB). Several recombinant enzymes were recovered that exhibit H2-uptake and -evolution ability. On the respective metagenomic fragments the orfs mostly exhibited very low similarity to hydrogenases or any known gene or no similarity at all, suggesting that there may be as yet undescribed hydrogenases out there.
Besides identifying and describing the newly discovered hydrogenase enzymes, hydrogenases with H2-evolving ability are applied to electrochemical cells. Their catalytic ability is used to produce hydrogen from water and store it in form of chemical energy. The hydrogenase are immobilized on electrodes with enlarged surface areas (cooperation with Prof. Julien Bachmann, FAU, Germany)
The project to identify new hydrogenases from hydrothermal vent metagenomes is currently financed by the German Science Foundation (DFG) (2018-2020).
Adam, N., Schlicht, S., Han, Y., Bechelany, M., Bachmann, J. & M. Perner (in review) Metagenomics meets Electrochemistry: utilizing the huge catalytic potential from the uncultured microbial majority for energy-storage. Frontiers in Bioetchnology and Bioengineering
Gonnella, G., Adam, & M. Perner (2019) Horizontal acquisition of hydrogen conversion ability and other habitat adaptations in the Hydrogenovibrio strains SP-41 and XCL-2. BMC Genomics 20, 339
Adam, N. & M. Perner (2018) Novel hydrogenases from deep-sea hydrothermal vent metagenomes identified by a recently developed activity-based screen. ISME Journal 12, 1225-1236
Adam, N. & M. Perner (2018) Microbially mediated hydrogen cycling in deep-sea hydrothermal vents. Frontiers in Microbiology doi: 10.3389/fmicb.2018.02873
Adam, N. & M. Perner (2017) Activity-based screening of metagenomic libraries for hydrogenase enzymes. Metagenomics – Methods and Protocols. W.R. Streit & R. Daniel (eds.), Springer