Archaea represent one of the three domains of life and were once thought to be restricted to extreme environments. This view has been dramatically changed over the last two decades through the discovery of abundant novel lineages of non-extremophilic archaea, their implication in the global nitrogen cycle and their laboratory cultivation. The recently-described phylum Thaumarchaeota includes autotrophic ammonia oxidisers, thus performing the rate-limiting step of nitrification, and frequently outnumbering their bacterial counterparts particularly in acidic soils. Nitrification is a fundamental component of the global nitrogen cycle and leads to significant fertiliser loss and atmospheric and groundwater pollution. Nitrification rates in acidic soils (pH<5.5), which comprise 30% of the world's soils, equal or exceed those of neutral soils. Paradoxically, autotrophic ammonia oxidizing bacteria and archaea, which perform the first stage in nitrification, do no grow in suspended liquid culture below pH 6.5, where ammonia availability is reduced by ionisation. This thesis describes the identification of pH as a major driver of Group 1.1 c thaumarchaeal abundance and diversity. Furthermore, it reports the cultivation of the first obligately acidophilic ammonia oxidiser, Candidatus Nitrosotalea devanaterra. This organism grows in the pH range 4.0 - 5.5 and represents a previously uncultivated lineage distributed across the globe in acidic soils. The physiology of Candida/us N. devanaterra was characterised, including the influence of organic acids (glyoxylate, pyruvate, oxaloacetate and a-ketoglutarate) on the growth.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:553840 |
| Date | January 2011 |
| Creators | Lehtovirta, Laura |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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