A great challenge for society is to find sustainable and clean means to conserve energy and produce commodities. One promising solution is the gasification of biomass wastes into syngas (mixture of CO, H2 and/or CO2). Syngas can subsequently act as substrate for microbial fermentation to produce valuable compounds. Carbon monoxide, the main component of syngas, is highly toxic towards most organisms, but it is also a favorable energy and carbon source for specific carboxydotrophic microbes. From a biotechnological perspective, this is very interesting since these microbes can be used by industry for the production of biochemicals and biofuels. In this project we want to explore high-temperature marine hydrothermal sediments for novel carboxydotrophic microbes, that could prove to be excellent candidates for syngas fermentation.