Deep-sea hydrothermal vents at mid-ocean ridges are a locus for sustained light of sufficient flux to support non-solar photosynthesis. These hydrothermal environments, thought to be likely places for the origin of life on Earth, produce a newly discovered bacterial species containing chorophyll and carotenoid pigments. The PIs are systematically searching for phototrophs at deep-sea vents, within vent plumes, and in the water column overlying vents. They focus on field sampling, shipboard analysis of pigments and determination of fluorescence properties of organic matter associated with sulfide mineral samples, microscopic evaluation of morphology and fluorescence properties of microbial cells in samples, isolation and cultivation of phototrophs, and identification of photosynthesis genes using PCR and DNA sequencing. Studying phototrophs in their natural habitat, the PIs are conducting the first phase of a multi-disciplinary program characterizing the distribution, biochemistry, and ecological significance of phototrophs at deep-sea hydrothermal vents.