Research Areas

The Amend Lab investigates microbial geochemistry across a range of environments — from the deep continental and marine subsurface to extraterrestrial analogs. Our work integrates field sampling, laboratory experiments, and thermodynamic modeling to understand how microorganisms harness energy and shape biogeochemical cycles in extreme settings.

Approach

Our group combines geochemical measurements, cultivation of novel microbes, and computational thermodynamic models to link microbial metabolism to environmental chemistry. Field sites span terrestrial hot springs, deep-sea hydrothermal vents, sub-seafloor boreholes, and continental drill holes — each offering a window into how life persists under energy limitation.

The Amend Laboratory investigates the intricate relationships between microorganisms and their geochemical surroundings, focusing on how microbial life persists and thrives in environments once thought too extreme for biological activity. By integrating field observations with controlled laboratory experiments and thermodynamic modeling, the research team seeks to quantify the energy yields available to microbes in diverse subsurface settings. This work spans continental aquifers, deep marine sediments, and fractured rock systems, each presenting unique challenges and opportunities for life. Understanding these fundamental bioenergetic constraints helps reveal the lower limits of life on Earth and provides a framework for interpreting microbial activity in seemingly inhospitable habitats across the planet.

A major research thrust involves the continental subsurface biosphere, where microbial communities inhabit deep terrestrial aquifers, mines, and fractured bedrock environments far below the surface. These dark, nutrient-limited ecosystems host microorganisms that rely on chemical energy sources such as hydrogen, iron, and sulfur compounds rather than sunlight. The lab's investigations into these deep continental settings aim to characterize the diversity, metabolic activity, and ecological interactions of these hidden microbial populations. By examining how energy availability shapes community structure and function, the research contributes to a broader understanding of life's distribution and resilience within the Earth's crust.

Parallel studies focus on the marine subsurface biosphere, where microorganisms are buried within ocean sediments accumulating on the seafloor over millions of years. These sedimentary habitats represent one of the largest reservoirs of microbial biomass on Earth, yet the energetic constraints on life in these deep, low-activity environments remain poorly understood. The Amend Lab explores how microbial metabolism proceeds under extreme pressure, limited nutrient supply, and gradual burial conditions. This research sheds light on the rates and pathways of biogeochemical cycling in marine sediments, including the transformation of carbon, sulfur, and nitrogen compounds over geological timescales.

Beyond Earthbound environments, the lab's research extends to astrobiology and the origin of life, using thermodynamic principles to evaluate where and how life might emerge on other planetary bodies. By studying extremophile microorganisms in analog environments such as hydrothermal systems and deep subsurface rocks, the team develops criteria for assessing the habitability of extraterrestrial settings. These investigations inform the search for life beyond Earth by establishing energetic and geochemical boundaries for microbial survival. The integration of field microbiology, experimental geochemistry, and theoretical modeling provides a comprehensive approach to understanding life's potential distribution throughout the solar system and beyond.