• Centre for Microbiology and Environmental Systems Science

  • CUBE - Computational Systems Biology

  • DOME - Microbial Ecology

  • EDGE - Environmental Geosciences

  • TER - Terrestrial Ecosystem Research


Latest publications

Sulfur and methane oxidation by a single microorganism.

Natural and anthropogenic wetlands are major sources of the atmospheric greenhouse gas methane. Methane emissions from wetlands are mitigated by methanotrophic bacteria at the oxic-anoxic interface, a zone of intense redox cycling of carbon, sulfur, and nitrogen compounds. Here, we report on the isolation of an aerobic methanotrophic bacterium, '' strain HY1, which possesses metabolic capabilities never before found in any methanotroph. Most notably, strain HY1 is the first bacterium shown to aerobically oxidize both methane and reduced sulfur compounds for growth. Genomic and proteomic analyses showed that soluble methane monooxygenase and XoxF-type alcohol dehydrogenases are responsible for methane and methanol oxidation, respectively. Various pathways for respiratory sulfur oxidation were present, including the Sox-rDsr pathway and the SI system. Strain HY1 employed the Calvin-Benson-Bassham cycle for CO fixation during chemolithoautotrophic growth on reduced sulfur compounds. Proteomic and microrespirometry analyses showed that the metabolic pathways for methane and thiosulfate oxidation were induced in the presence of the respective substrates. Methane and thiosulfate could therefore be independently or simultaneously oxidized. The discovery of this versatile bacterium demonstrates that methanotrophy and thiotrophy are compatible in a single microorganism and underpins the intimate interactions of methane and sulfur cycles in oxic-anoxic interface environments.

Gwak JH, Awala SI, Nguyen NL, Yu WJ, Yang HY, von Bergen M, Jehmlich N, Kits KD, Loy A, Dunfield PF, Dahl C, Hyun JH, Rhee SK
2022 - Proc Natl Acad Sci U S A, 32: e2114799119

Broad- and small-scale environmental gradients drive variation in chemical, but not morphological, leaf traits of vascular epiphytes

  1. Variation in leaf functional traits along environmental gradients can reveal how vascular epiphytes respond to broad- and small-scale environmental gradients. Along elevational gradients, both temperature and precipitation likely play an important role as drivers of leaf trait variation, but these traits may also respond to small-scale changes in light, temperature and humidity along the vertical environmental gradient within forest canopies. However, the relative importance of broad- and small-scale environmental gradients as drivers of variation in leaf functional traits of vascular epiphytes is poorly understood.
  2. Here, we examined variation in morphological and chemical leaf traits of 102 vascular epiphyte species spanning two environmental gradients along Cofre de Perote mountain in Mexico: (i) a broad-scale environmental gradient approximated by elevation as well as by species' lower and upper elevational limits, and (ii) small-scale environmental gradients using the relative height of attachment of an epiphyte on a host tree as a proxy for variation in environmental conditions within the forest canopy. We also assessed whether variation in morphological and chemical leaf traits along these gradients was consistent across photosynthetic pathways (CAM and C3).
  3. Broad- and small-scale environmental gradients explained more variation in chemical traits (marginal R2: 11%–89%) than in morphological traits (marginal R2: 2%–31%). For example, leaf carbon isotope signatures (δ13C), which reflects water-use efficiency, varied systematically across both environmental gradients, suggesting a decrease in water-use efficiency with increasing lower and upper elevational limits and an increase in water-use efficiency with relative height of attachment. The influence of lower and upper elevational limits on trait variation differed between photosynthetic pathways, except for leaf dry matter content and leaf nitrogen-to-phosphorus ratio. Contrary to our expectations, broad- and small-scale environmental gradients explained minimal variation in morphological leaf traits, suggesting that environmental conditions do not constrain morphological leaf trait values of vascular epiphytes.
  4. Our findings suggest that assessing multiple drivers of leaf trait variation among photosynthetic pathways is key for disentangling the mechanisms underlying responses of vascular epiphytes to environmental conditions.
Guzmán-Jacob V, Guerrero-Ramírez NR, Craven D, Paterno GB, Taylor A, Kromer T, Wanek W, Zotz G, Kreft H
2022 - Functional Ecology, 36: 1858-1872

Soil carbon loss in warmed subarctic grasslands is rapid and restricted to topsoil

Global warming may lead to carbon transfers from soils to the atmosphere, yet this positive feedback to the climate system remains highly uncertain, especially in subsoils (Ilyina and Friedlingstein2016Shi et al.2018). Using natural geothermal soil warming gradients of up to +6.4C in subarctic grasslands (Sigurdsson et al.2016), we show that soil organic carbon (SOC) stocks decline strongly and linearly with warming (−2.8 t ha−1C−1). Comparison of SOC stock changes following medium-term (5 and 10 years) and long-term (>50 years) warming revealed that all SOC stock reduction occurred within the first 5 years of warming, after which continued warming no longer reduced SOC stocks. This rapid equilibration of SOC observed in Andosol suggests a critical role for ecosystem adaptations to warming and could imply short-lived soil carbon–climate feedbacks. Our data further revealed that the soil C loss occurred in all aggregate size fractions and that SOC stock reduction was only visible in topsoil (0–10 cm). SOC stocks in subsoil (10–30 cm), where plant roots were absent, showed apparent conservation after >50 years of warming. The observed depth-dependent warming responses indicate that explicit vertical resolution is a prerequisite for global models to accurately project future SOC stocks for this soil type and should be investigated for soils with other mineralogies.

Verbrigghe N, Leblans NIW, Sigurdsson BD, Vicca S, Fang C, Fuchslueger L, Soong JL, Weedon JT, Poeplau C, Ariza-Carricondo C, Bahn M, Guenet B, Gundersen P, Gunnarsdóttir GE, Kätterer T, Liu Z, Maljanen M, Marañon-Jimenez S, Meeran K, Oddsdóttir ES, Ostonen I, Schiestl RH, Richter A, Sardans J, Sigurðsson P, Torn MS, Van Bodegom PM, Verbruggen E, Walker TWN, Wallander H, Janssens IA
2022 - Biogeosciences, 19: 3381-3393