Microbial carbon cycling in marine shallow-water hydrothermal systems

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Hydrothermal vent systems are increasingly recognized as extreme environments of tremendous scientific importance. Their study is of great significance to geochemistry, geobiology and microbiology, because they act as windows into the Earth and its multiple linkages between the bio- and geosphere. The limits of life as well as its potential origin are two of the greatest puzzles in biogeosciences, which one can address via the study of hydrothermal systems. The study of the extremophiles inhabiting marine shallow-water hydrothermal vents (MSWHV) presents an enormous opportunity, because they (1) provide a window into a microbiome characterized by high metabolic versatility and unique adaptations to extreme conditions, they (2) are vastly understudied, and they (3) combine easy accessibility with a wide range of geological, chemical, and biological processes similar to those taking place at deep-sea vents. I propose a multidisciplinary approach to study autotrophic microorganisms and the processes mediated by them. The main study site will be the arsenic-rich hydrothermal system off Milos, Greece, but additional MSWHV will be studied off Dominica and Taiwan to investigate variable geochemical environments. This task requires an interdisciplinary frontier research approach at the scale of an Emmy Noether-Program, involving (bio-)geochemistry and microbiology. My central research strategy is based on the information encoded in structural and isotopic properties of membrane lipids of the indigenous organisms. This will be combined with stable isotope probing experiments investigating uptake of tracer into biomarker and rRNA. This approach will be complemented by functional gene analyses allowing further insights into metabolisms. Selected sites will furthermore be subject to metagenomic analyses. Detailed biogeochemical characterization of the sites will complement the research approach. Attempts to enrich organisms with unique metabolic pathways (e.g. autotrophic arsenite oxidizers) from sediments will complete these studies. The proposed research builds on a solid foundation of work by the proponent and provides furthermore a perfect basis for establishing the PI as leader in processorientated microbial ecology of extreme environments.