Diversity of autotrophic organisms and their carbon fixation pathways at hydrothermal vent systems on the Arctic Mid-Ocean Ridge

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The fixation of carbon dioxide into biomass is arguably the most fundamental biological process, and a prerequisite for life on earth. While photosynthetic organisms account for the majority of global carbon fixation via the reductive pentose phosphate cycle, marine hydrothermal vent systems have gained research attention as hot spots for life based on sunlight-independent prokaryotic carbon fixation. The steep gradients of different inorganic energy substrates at hydrothermal vents create ecological niches for diverse autotrophic organisms.An abundance of genomic data has been recovered from hydrothermal sites and uncovered an unexpected microbial diversity over the last years, but functional data regarding metabolism and activity is still scarce due to difficult sampling and culturing of microorganisms from hydrothermal vents. This discrepancy prevents an exhaustive interpretation of genomic data and limits the accuracy of metabolic models that describe these ecosystems and assess their role in the global carbon cycle. Here I propose an in-depth study of the microbial primary producers and their metabolic strategies at recently discovered hydrothermal vent fields along Arctic Mid-Ocean Ridge (AMOR), which I will carry out in cooperation with my host Prof. Ida Steen, who is a group leader at the K. G. Jebsen Centre for Deep Sea Research at the University of Bergen in Norway. I will carry out differentiated sampling of different vent sites on the AMOR, shipboard incubations simulating natural conditions, stable isotope probing, metagenomics and a detailled bioinformatic analysis in order to identify autotrophic organisms and their carbon fixation pathways, and to estimate their contribution towards primary production.This multi-angled research approach, integrating functional with omics data, allows me to draw conclusions about the factors that influence the distribution of different carbon fixation pathways in nature, and about how they are adapted to diverse ecological niches. Additionaly, it enables me to search for novel and unexpected carbon fixation strategies. This study will contribute to the ongoing efforts to establish the hydrothermal sites on the AMOR as model systems, and it is a step towards a comprehensive picture of autotrophic carbon fixation at marine hydrothermal vent systems, from enzymes to ecosystems.