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Receives postdoctoral fellowship from the German Research Foundation

Dr. Achim Mall recently received a two year postdoctoral fellowship from the German Research Foundation. He will be working with carbon fixation in hydrothermal systems as part of the microbiology group at the K.G. Jebsen Centre. We congratulate and welcome him to our centre!

Dr. Achim Mall
Photo:
Achim Mall.

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Mall describes his project "Diversity of autotrophic organisms and their carbon fixation pathways at hydrothermal vent systems on the Arctic Mid-Ocean Ridge" as follows:

The dense ecosystems that thrive in total darkness around hydrothermal vents in the deep ocean owe their existence to the activity of chemosynthetic microorganisms, which harness energy from hot volcanic fluids and fix carbon dioxide to build their cells. Their biomass in turn serves as a source of energy and organic carbon for all other organisms living there. Compared to surface habitats, where almost all organic carbon is fixed by photosynthetic organisms, the chemosynthetic communities at vent sites are diverse and highly structured in ecological niches. These are shaped by the availability of different energy-rich substrates in hydrothermal fluids, like hydrogen, methane, ammonium or reduced sulfur compounds, and by gradients of temperature, pH and oxygen, which in turn result from the mixing of hot, energy-rich hydrothermal fluids with cold, oxygen-rich seawater.

The carbon fixation pathways employed by microorganisms that inhabit hydrothermal vent systems are equally diverse and mirror their lifestyles. Five of the six known carbon fixation pathways have been described in these habitats, each representing an adaption to a certain ecological niche, and different characteristics such as energy demands, thermostability or oxygen tolerance. In recent years, metagenomic studies have yielded a wealth of genome sequence information about the chemosynthetic microbial communities at hydrothermal systems, and have uncovered an unanticipated diversity of microorganisms that had previously been overlooked.

During my research fellowship in Prof. Ida Steen's group at the K. G. Jebsen Centre for Deep Sea Research, I will use a method called ‘stable isotope probing’ to gain knowledge about the metabolic activity and relative contribution to carbon fixation of microorganisms at hydrothermal systems along the Arctic mid-ocean ridge. I will sample microorganisms from different hydrothermal sites and incubate them on shipboard under conditions simulating the different ecological niches, in the presence of carbon dioxide that is labelled with 13-C, a stable carbon isotope. Organisms that are able to fix this carbon will incorporate it into their DNA, and by separating and sequencing the DNA that is enriched in this isotope, I can draw conclusions about which members of the microbial community are actively fixing carbon under the chosen incubation conditions. I will then correlate this information to genome sequences and gene expression data in order to learn about which carbon fixation pathways are most active in the different ecological niches at hydrothermal vents, and which environmental factors shape their distribution. This approach also allows me to find novel, unexpected carbon fixation pathways, where stable isotope probing data shows the assimilation of carbon dioxide, but where none of the recognized pathways are present or expressed. I will work together with Prof. Håkon Dahle to develop bioinformatic tools that allow us to find patterns in the distribution of genes and pathways in big genomic datasets and help us to recognize the presence novel carbon fixation strategies.