Understanding How Microbes Affect Earth's Biogeochemical Cycling

DATE: April 2020
Dartmouth College | Earth Science
Beverly Chiu, Research Staff

The Leavitt Lab at Dartmouth College studies geomicrobiology and geochemistry to understand how microbes affect Earth’s biogeochemical cycling. One of our major research projects investigates microbial methane production. Methane is a greenhouse gas with powerful global warming potential, making it important to understand the relative contributions of different methane sources. To that end, our goal is to measure the bulk and clumped isotopic compositions of methane molecules derived from various microbial pathways. These measurements provide the unique isotopic fingerprints associated with each specific microbial source and can ultimately be used to decipher source contributions of methane to the atmosphere.

Toward the goal of distinguishing microbial contributions to atmospheric methane, our lab conducts experiments to capture and analyze methane from different microbial pathways. This involves capturing microbially-produced methane in the headspace of sealed culture vessels and using the final headspace for isotopic analysis. A crucial intermediate step before isotopic measurements is to monitor methane production in our cultures during growth. This requires regular sampling of culture headspace to quantify methane by gas chromatography. Hamilton gas-tight syringes are invaluable in this process to avoid gas loss between culture sampling and GC injection. Additionally, many of our cultures produce methane in relatively low abundances making it more critical to avoid sample loss. For such cases, we use Hamilton gas-tight syringes with sample locks to prevent such losses and ensure accurate GC measurements. Overall, Hamilton gas-tight syringes are indispensable tools for our lab’s efforts to characterize and differentiate microbially-produced methane.

The Leavitt Lab prides itself on developing the research skills of its students while using novel geochemical and microbiological approaches to answer questions about the Earth’s past and present state. We are a newer and smaller lab, which allows us to provide substantial individual support and mentoring to each of our graduate and undergraduate students. We feel this has been key to our research accomplishments and toward our dedication to producing excellent research scientists.