Microbial Community Structure and Function in Peat Soil

Ines Mandic-Mulec*, Luka Ausec, Tjaša Danevčič, Špela Levičnik-Höfferle, Vesna Jerman and Barbara Kraigher

University of Ljubljana, Biotechnical Faculty, Department of Food Science and Technology, Chair of Microbiology, Večna pot 111, SI-1000 Ljubljana, Slovenia

Article history:
Received October 29, 2013
Accepted April 30, 2014

Key words:
microbial community, microbial diversity, peatland, greenhouse gas, nitrification, denitrification, methanogenesis, methanotrophy, laccase, amoA

Summary:
Many peatlands in Europe have been subjected to land reclamation and systematic drainage, which have substantially affected nutrient cycles in the soil. This work reviews published studies on microbial processes linked to carbon and nitrogen transformations in the soils of the Ljubljana marsh, a drained peatland positioned close to Ljubljana, the capital of Slovenia. This region is known for its dramatic diversity of animal and plant life, but below ground it hides diverse bacterial and archaeal communities that are highly responsive to environmental changes and make the Ljubljana marsh soils a good source of N₂O and CO₂, and a sink for CH₄. Methanogenesis is highly restricted in these soils due to competition for electron donors with iron reducers. In addition, methane is efficiently removed by methanotrophs, which are highly active, especially in the soil layers exposed to the changing water table. Denitrification is limited by electron acceptors and in deeper soil layers also by carbon, which becomes more recalcitrant with depth. Nitrification involves bacterial and archaeal ammonia oxidisers with ammonia oxidation rates being among the highest in the world. Interestingly, ammonia-oxidising Thaumarchaeota in acidic bog soils thrive only on ammonia released through mineralisation of organic matter and are incapable of oxidising added mineral ammonia. The soils of the Ljubljana marsh are rich in bacterial laccase-like genes, which may encode enzymes involved in lignin degradation and are therefore interesting for bioexploitations. Future challenges involve designing studies that will reveal specific physiological functions of phenol oxidases and other enzymes involved in peat transformations and address relations between microbial diversity, function and ecosystem responses to anthropogenic disturbances.

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