Microbial thiocyanate biodegradation: an unexplored nexus for the sulphur, nitrogen and carbon biogeochemical cycles

Biogeochemical Cycles

IAP2-21-397

Overview

In wetlands and estuarine sediments, microorganisms degrade thiocyanate (SCN-) to form carbonyl sulphide (COS) and cyanate (CNO-) (Fig. 1). These molecules represent an unexplored and critical nexus of three major elemental cycles [1-3]: sulphur (S), nitrogen (N) and carbon (C), which:
• strongly influences atmospheric, terrestrial and ocean chemistry,
• provides critical requirements for primary productivity, cell growth and metabolic energy, and
• sustains diverse and highly interconnected sedimentary microbial communities.
Despite the importance of COS as a major S-bearing trace gas with a central role in stratospheric sulphate aerosol production, the process of microbial COS degradation is very poorly understood [4]. Microbial cycling of COS in the open ocean and coastal waters is even less understood, as are fluxes of COS in the global S cycle. Likewise, a recent study found that, in oligotrophic seawater, CNO- acts as a significant source of N for nitrification [5], suggesting CNO- plays a more important role in the global N cycle than previously realised.
This project aims to: increase our knowledge of the distribution, phylogeny and metabolic role(s) of microorganisms responsible for the biodegradation of SCN-, CNO- and COS in wetland sediments.

Methodology

In wetlands and estuarine sediments, microorganisms degrade thiocyanate (SCN-) to form carbonyl sulphide (COS) and cyanate (CNO-) (Fig. 1). These molecules represent an unexplored and critical nexus of three major elemental cycles [1-3]: sulphur (S), nitrogen (N) and carbon (C), which:
• strongly influences atmospheric, terrestrial and ocean chemistry,
• provides critical requirements for primary productivity, cell growth and metabolic energy, and
• sustains diverse and highly interconnected sedimentary microbial communities.
Despite the importance of COS as a major S-bearing trace gas with a central role in stratospheric sulphate aerosol production, the process of microbial COS degradation is very poorly understood [4]. Microbial cycling of COS in the open ocean and coastal waters is even less understood, as are fluxes of COS in the global S cycle. Likewise, a recent study found that, in oligotrophic seawater, CNO- acts as a significant source of N for nitrification [5], suggesting CNO- plays a more important role in the global N cycle than previously realised.
This project aims to: increase our knowledge of the distribution, phylogeny and metabolic role(s) of microorganisms responsible for the biodegradation of SCN-, CNO- and COS in wetland sediments.

Project Timeline

Year 1

1a) Sampling and processing of sediment samples
1b) Quantification of (bio)geochemical analytes
1c) Sediment microcosm experiments (with acquisition and storage of subsamples for DNA sequencing/analysis)
1d) Write-up first manuscript

Year 2

2a) DNA sequencing and genome-resolved metagenomics/bioinformatics analyses of sediment microcosm experiments
2b) Setup of stable isotope probing (SIP) microcosm experiments
2c) Write-up 2nd manuscript
2d) Attend 1st scientific conference (domestic, likely Geomicrobiology Network Meeting, UK)

Year 3

3a) SIP microcosm experiments and consequent geochemical analyses/molecular microbiological studies

Year 3.5

3b) Write-up 3rd manuscript
3c) Present culmination of doctoral research at 2nd scientific conference (international; likely ISME Conference, location TBA))

Training
& Skills

The PhD student will learn fieldwork skills, sample handling and processing techniques, analytical geochemistry methods, molecular biology and bioinformatics approaches, experimental design, scientific writing and science communication.

References & further reading

1. Watts, S.F., 2000. The mass budgets of carbonyl sulfide, dimethyl sulfide, carbon disulfide and hydrogen sulfide. Atmospheric Environment, 34(5), pp.761-779.
2. Palatinszky, M., Herbold, C., Jehmlich, N., Pogoda, M., Han, P., von Bergen, M., Lagkouvardos, I., Karst, S.M., Galushko, A., Koch, H. and Berry, D., 2015. Cyanate as an energy source for nitrifiers. Nature, 524(7563), pp.105-108.
3. Widner, B., Mulholland, M.R. and Mopper, K., 2016. Distribution, sources, and sinks of cyanate in the coastal North Atlantic Ocean. Environmental Science & Technology Letters, 3(8), pp.297-302.
4. Watts, M.P., Spurr, L.P., Lê Cao, K.A., Wick, R., Banfield, J.F. and Moreau, J.W., 2019. Genome-resolved metagenomics of an autotrophic thiocyanate-remediating microbial bioreactor consortium. Water research, 158, pp.106-117.
5. Palatinszky, M., Herbold, C., Jehmlich, N., Pogoda, M., Han, P., von Bergen, M., Lagkouvardos, I., Karst, S.M., Galushko, A., Koch, H. and Berry, D., 2015. Cyanate as an energy source for nitrifiers. Nature, 524(7563), pp.105-108.

Further Information

John Moreau, john.moreau@glasgow.ac.uk

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