Thriving Microbial Life in Ancient Groundwater Deep Inside Earth’s Crust

Did you know that the earth beneath your feet is teeming with life? Imagine yourself standing outside. If you started digging, at some point beneath the soil you would eventually hit hard rock—that is the bedrock forming the Earth’s crust. Even this seemingly solid material has cracks and pores that contain groundwater (water that is held in the ground), and where there is water, there can be life. Tiny, single-celled creatures called microbes survive and thrive in many environments on Earth that are inhospitable for all other life forms. This is also the case with deep bedrock, where only microbial life is possible. As sunlight and plant products are not available in this environment, microbes have to use chemical compounds for their food and energy sources. In this study, we investigated the preferred food for microbes living in the bedrock. We discovered that hydrogen is an important energy source for deep microbes, and that the microbial communities are able to change so that they can survive under changing environmental conditions.