Research Projects


Field work areas / Participation in expeditions

2016 RV Atlantis cruise AT37-06 with submersible ALVIN; Hydrothermal vents of the Guaymas Basin, Gulf of California
  Polarstern cruise PS101, Karasik Seamount, Gakkel Ridge, Arctic: Aim: Biogeochemistry of the vent plume
2015 RV Meteor cruise 114; Methane and heavy oil seepage in the Campeche hydrocarbon province, Gulf of Mexico; Aim: Diversity and microbiology of hydrocarbon-degrading microorganisms
2014  RV Polarstern cruise 86 (ARKXXVIII); Aurora Vent Field, Gakkel Ridge, Arctic, biogeochemistry of vent systems associated with ultra-slow spreading ridges. Aim: Vent-associated microbial activity in the water column
2009 RV Atlantis cruise AT15-45 with submersible ALVIN; Hydrothermal Vents of the Guaymas Basin, Gulf of California; Aim: Anaerobic oxidation of methane under thermophilic conditions
  Himmersfjärden, Baltic Sea; Carbon dynamics in Baltic Sea fjord sediments; Aim: Application of dual stable isotope probing
  RV Sonne cruise 191; Cold seeps of the Hikurangi margin, New Zealand (new vents project)
2006 RV Meteor cruise M67-2b; Chapopote asphalt volcano, Campeche hydrocarbon province, Gulf of Mexico
2005 RV Alkor cruise 267; North Sea (Nor­we­gen Shelf), EXO­CET
  RV Heincke cruise 208; Gullfaks, Tommeliten, North Sea


Microbial life at hydrothermal vents of the Guaymas Basin, Gulf of California

Hydrothermal vents are hot spots of microbial life. At Guaymas Basin, situated on the East Pacific Rise, magma intrusions caused pore water convection and thermogenic release of methane and higher hydrocarbons from organic matter. In contact to seawater minerals precipitate from emitted fluids and form impressive chimney structures. Reduced compounds in the fluids are the basis for a large number of microorganisms forming colorful mats on the seafloor (see picture).
My main goals here are (I) the quantification of microbial processes such as methanotrophy, methanogenesis and sulfate reduction under present temperatures, (II) the identification of microorganisms involved in these processes and (III) lipid formation in the different temperature regimes.
Notre Dame
‘Notre Dame’ – A cascade of hot fluid emitting chimneys covered with colorful microbial mats (Hydrothermal Vents of the Guaymas Basin)

Microbial alkane degradation at asphalt volcanoes

The Campeche Knolls are hotspots of hydrocarbon emissions from deep thermogenic reservoirs to the seafloor. On Meteor Expedition ME114 (Chief Scientists G. Bohrmann & Heiko Sahling) we mapped heavy oil and gaseous hydrocarbon seepage at different asphalt volcanoes. Those emissions fuel a variety of microorganisms and chemosynthetic fauna. In the home laboratories we study microbial communites involved in the degradation of these compounds. We aim to get a holistic picture on the diversity and functioning on microbial communities involved in the anaerobic oxidaiton of hydrocarbons.

Dual stable isotope probing in subsurface sediments

Molecular methods revealed that the deep subsurface hosts a large microbial diversity and harbors up to 1/3 of all microbial cells on earth. However, the basis of metabolic activity and energetics of most of these microorganisms are only poorly understood. We applied dual stable isotope probing with deuterated water (D2O) and 13C-labeled bicarbonate (13CDIC). Assessment of D and 13C assimilation into microbial membrane lipids allows the quantification of total lipid production and inorganic carbon assimilation rates without addition of artificial energy sources. Furthermore we can determine the role of heterotrophic and autotrophic carbon fixation in the sediment. For our first study site, the Swedish bay “Himmersfjarden” we were able to demonstrate predominantly heterotrophic carbon fixation. Furthermore, we demonstrated that in these young sediments bacteria are much more active than archaea. The results of this and ongoing studies aim a further understanding of the role of archaea and bacteria in their particular environment. Recent dual-SIP projects include carbon fixation in vent systems and deep-sea sediments.

In a second dual-SIP project we studied microbial carbon fixation in hydrothermal sediments from the Guaymas Basin. We found that the methane-oxidizing archaea (ANME) and their partner bacteria are complete autotrophs, meaning they use methane only as energy source but fix their carbon completely from inorganic carbon. The chemoorganoautotrophic nature of ANME archaea has to be kept in mind when interpreting natural carbon isotopic signatures.

Characterizing the interaction of microorganisms mediating the anaerobic oxidation of methane

From Guaymas sediments, we successfully enriched anaerobic methanotrophs that perform anaerobic oxidation of methane at elevated temperatures up to 70°C. The enriched thermophilic communites are dominated by distinct groups of ANME-1 and HotSeep-1 partner bacteria (Holler et al., 2011). By combining physiological experiments, electron microscopy, and genomics we identified direct interspecies electron transfer mediated by nanowire-like connections as driver for the interaction of ANME-1 archaea and their partner bacteria. Currently, we test our model on different related microbial associations.

AOM consortia
Fluorescence micrograph of microorganisms of anaerobic archaea (red) and partner bacteria (green) enriched under thermophilic conditions from Guaymas Basin sediments (Holler et al. 2011, The ISME Journal)
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