Understanding thermophilic ammonia-oxidizing archaea environments across extreme redox gradients
Fackrell, Laura Elizabeth
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New understanding of key microbial players in the nitrogen cycle such as the discovery of ammonia-oxidizing archaea (AOA) has sparked a plethora of research aimed at nitrogen cycle processes. Evidence for AOA has been specifically detected in hot springs of Uzon Caldera, Kamchatka Russia. Samples were collected from Orange Thermal Field (OTF) and other thermal fields in Uzon to gain greater understanding of environments in which AOA are found. The geochemistry, microbial communities, mineralogy were examined at OTF from both oxidized and reduced zones. It was hypothesized that crenarchaeol would be more abundant where oxygen and nutrients NH4+ and Cu are more abundant. Instead, a higher abundance of crenarchaeol was observed where smectites were common despite lower Cu and Oxygen levels. Smectites have a greater potential to bind NH4+ and metal cations. It is proposed that in OTF the presence of NH4+-bearing smectites in reduced zones provides a more favorable environment due to the acidity of sediments resulting in greater AOA abundance.