The production of organic chemicals from inorganic source substances by an autotrophic organism that utilizes chemical energy (e.g. from the oxidation of hydrogen sulfide) rather than sunlight (as in photosynthesis). A few highly specialized chemosynthetic bacteria occupy odd niches such as geyser pools or anaerobic muck from the bottom of watercourses. In a few places, complete ecosystems have developed around chemosynthesis, as those surrounding thermal springs in deep ocean trenches, called hydrothermal vents.