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Title: Ecological insights into unexplored Archaea through environmental ecophysiology, single-cell genomics and cultivation
Author: Weber, Eva
ISNI:       0000 0004 6062 5424
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2017
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Unexplored soil microorganisms present a potential reservoir of novel metabolisms that may contribute to important ecosystem processes. One example of unexplored soil microorganisms is Group 1.1c Thaumarchaeota that inhabit many acidic soils and have unknown metabolic potential. To gather insights into the environmental role of Group 1.1c Thaumarchaeota, several strategies were employed in this study. The ecophysiology of Group 1.1c Thaumarchaeota was investigated in Scottish pine forest soil microcosms. Although growth was observed, it was not associated with ammonia oxidation and the functional gene amoA could not be detected. In addition, environmental studies and genomic predictions suggested existence of both aerobic and anaerobic metabolisms in these microorganisms. However, a microcosm experiment performed in this study demonstrated only aerobic growth of Group 1.1c Thaumarchaeota originating from both aerobic and anaerobic soils. The metabolic pathways of Group 1.1c Thaumarchaeota were then investigated by developing and applying a targeted single-cell genomic approach. The genomic data obtained indicated four metabolic pathways that may be important for cellular growth: fatty acid ß-oxidation, nitrate assimilation, ammonification and taurine oxidation. Based on these metabolic predictions, a specific archaeal cultivation medium was designed and its inoculation with pine forest soil led to the enrichment and successful isolation of the first Group 1.1c thaumarchaeotal representative, "Candidatus Terracidus borealis", which is a small coccoid archaeon (0.5 µm diameter). T. borealis requires nitrate and an organic source of carbon for its growth, however it does not oxidise ammonia as a source of energy and therefore represents the first heterotrophic non-ammonia-oxidising Thaumarchaeota. The isolation of T. borealis extends the known metabolisms of soil Thaumarchaeota and suggests the involvement of Thaumarchaeota in both autotrophic and heterotrophic soil processes.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Soil microbiology ; Ecophysiology ; Genomics