ECR Feature: Magdalena Nagler on methanogenic archaeal assemblages

Magdalena is a postdoc at the Institute of Microbiology, University Innsbruck, Austria. She is a microbial ecologist interested in the ecosystem services and industrial applications of micro-organisms. Magdalena shares her recent work on characterising different methanogenic archaeal assemblages from stream habitats across Europe.

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Institute. Institute of Microbiology, University Innsbruck, Austria

Major research themes. Microbial ecology all-rounder, highly interested in anaerobic habitats and organisms, especially methanogenic archaea and anaerobic fungi, both potential key players when it comes to full exploitation of resources in renewable energy production.

Current study system. I work on the growth requirements and exploitation potential of Neocallimastigomycota, a group of archaic, anaerobic fungi. This group of fungi was originally found in the bovine rumen and is known to produce a large set of enzymes with the potential to break down otherwise hard-to-degrade plant fibres. Knowing the needs of these microorganisms will allow better utilisation of natural resources in anthropogenic context, such as how to more efficiently use maize or corn straw in renewable energy production (e.g., biogas or bioethanol).

Ora, northern Italy

Recent paper in JBI. Nagler, M, Praeg, N, Niedrist, GH, et al. Abundance and biogeography of methanogenic and methanotrophic microorganisms across European streams. J Biogeogr. 2021; 48: 947– 960.

Motivation behind this paper. During my PhD, I became part of a collaborative European freshwater science project for early career researchers that aimed to study CO2 fluxes from European running waters (EuroRun). This led to a follow-up project focussing on sediment methane production in streams (EuroMethane). Utilizing the network of early career scientists from all over Europe, many streams could be sampled within a short time span, providing an exciting sample set that allowed us to investigate the role of these ecosystems in carbon cycling and retaining heavy metals. Having a solid background in microbial biogeography, microbial community analyses and methanogenic archaeal assemblages, I elaborated a concept together with project leader, Pascal Bodmer, to directly investigate how methanogenic and methanotrophic microorganisms contribute to methane production and oxidation rates of stream sediments across Europe.

Sampling of stream sediments using cut-off syringes.

Key methodologies. The first key methodology was the simultaneous sampling of 16 rivers in 10 European countries that required a lot of coordination to have everyone on the same track and ensure comparable results. During sampling, we aimed to gather as much information as possible on fine and large scale environmental constraints of each sampling point, so that we could link those factors to certain microbial community compositions. Fine scale variables included, for example, sediment grain size, nutrient availability and physico-chemical conditions; large-scale variables involved the characterisation of land-use types within the river’s catchment and of the river’s general ecological and hydrodynamic features.

The big aim of our study was a holistic examination of the sediment-associated methane-cycle that involved not only a direct measurement of potential methane production and oxidation, but also a qPCR-based direct quantification of genes associated to methane -producing and -oxidizing microorganisms coupled with an in-depth 16S rDNA-based taxonomic characterisation.

Major results. Methanogenic and methanotrophic communities mainly grouped into three habitat types, namely (I) warm streams with large stream areas, draining catchments with high proportions of agricultural and urban land cover, (II) cold, medium‐ to small‐sized streams with less agricultural and urban land use within their catchment and (III) high‐order and high discharge streams draining large catchments. Such distinguishable microbial communities suggest that future climate‐ and land use changes may influence the prevailing microbes involved in the stream‐related methane cycle. Increasing water temperatures from climate change, in combination with agricultural intensification and urban land use, might thereby lead to higher abundances of highly efficient hydrogenotrophic methane producers (i.e., Methanospirillaceae,Methanobacteriaceae and Methanosarcinaceae). It is still unclear how increasing anthropogenic disturbances might affect methane consumers, but we believe that there will be a net increase of methane released from streams in the future.

Unexpected outcomes. When we compared the qPCR data to the measured methane production and oxidation rates, we found a significant relationship between methanogenic archaeal abundance and potential methane production, but failed to find a relationship between methanotrophic bacterial abundance and methane oxidation potentials. We argued that this discrepancy might arise from the heterogeneity of microorganisms with the capacity to oxidize methane. This group not only includes bacteria, but also some recently described anaerobic methane oxidizing archaea (ANME). Most of these microorganisms are not exclusively oxidizing methane as source of energy, but can perform other ways of energy production, which would obscure the signal between the abundance of methanotrophic microogranisms and the measured methane oxidation potential. This hypothesis has yet to be tested!

Tratzberg, Austria

Next steps. We are currently working on an article processing the findings from CO2 flux measurements from running waters (EuroRun). The measurements were performed during day and night and clearly showed that streams emit more CO2 at night, a fact that so far has not been considered in global CO2-budget calculations. We are also working on a second article of the EuroMethane project, which focuses on the magnitudes and drivers of methane production and oxidation in streams across Europe.

If you could study any organism on Earth, what would it be? The holy grail of any mycologist is to reveal the secret about fruiting body development in edible, but not yet cultivable mushrooms such as Boletus edulis. Unfortunately, this is currently not my expertise, but if I could, I would jump right into disclosing this secret that might finally satisfy my craving for fresh porcini!

Published by jbiogeography

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