Thomas Freitag

The James Hutton Institute, Ecological Sciences / Soil & Microbial Ecology, research scientist

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My general research interests are the relationships between biogeochemical cycling and microbial processes. I specialize in the molecular analysis of microbial DNA signatures (abundance and phylogeny) and their functional activity (mRNA expression) within soil and sediment ecosystems. I have a long standing interest in microbial N- (nitrification and denitrification) and C- cycling (methanogenesis and methane oxidation) and the involvement of slow growing acido- and actinobacteria to soil organic matter degradation processes. Current research includes the relationship of Sphagnum spp. associated methanotroph activity to peat 13CO2- flux isotope signatures and the application of deep sequencing techniques (Roche 454 & Illumina) for assessing microbial biodiversity and functions in soils.
Most recently I have developed interest in the application of comparative metagenomic and metatranscriptomic sequencing approaches to investigate changes in microbial community metabolic capacity and pathways under environmental change scenarios. These approaches have been identified as most promising for understanding the regulation of microbial activities in response to environmental drivers and defined manipulations.
Address: The James Hutton Institute
Craigiebuckler
Aberdeen AB15 8QH
Scotland UK

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Thomas Freitag

Pierre Offre

University of Vienna

Ines Mandic-mulec

University of Ljubljana, Biotechnical Faculty

nejc stopnišek

University of Washington

Zucong Cai

Man-Young Jung

Verónica Molina T.

Marcela Perez Hernandez

Yoshihisa Suyama

Patricia Quadros

Universidade Federal do Rio Grande do Sul

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Soil

Ammonia oxidation, as the first step in the nitrification process, plays a central role in the gl... more Ammonia oxidation, as the first step in the nitrification process, plays a central role in the global cycling of nitrogen. Although bacteria are traditionally considered to be responsible for ammonia oxidation, a role for archaea has been suggested by data from metagenomic studies and by the isolation of a marine, autotrophic, ammonia-oxidizing, non-thermophilic crenarchaeon. Evidence for ammonia oxidation by non-thermophilic crenarchaea in marine and terrestrial environments is largely based on abundance of bacterial and archaeal ammonia monooxygenase (amo) genes, rather than activity. In this study, we have determined the influence of temperature on the response of ammonia-oxidizing bacteria and archaea in nitrifying soil microcosms using two approaches, involving analysis of transcriptional activity of 16S rRNA genes and of a key functional gene, amoA, which encodes ammonia monooxygenase subunit A. There was little evidence of changes in relative abundance or transcriptional activity of ammoniaoxidizing bacteria during nitrification. In contrast, denaturing gradient gel electrophoresis analysis of crenarchaeal 16S rRNA and crenarchaeal amoA genes provided strong evidence of changes in community structure of active archaeal ammonia oxidizers. Community structure changes were similar during incubation at different temperatures and much of the activity was due to a group of non-thermophilic crenarchaea associated with subsurface and marine environments, rather than soil. The findings suggest a role for crenarchaea in soil nitrification and that further information is required on their biogeography.

Thomas Freitag

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