Movile Cave is a totally unique environment, situated in the south of Romania. Not only is Movile Cave a fascinating example of a bacterially-driven environment, it is also completely isolated from the outside world – it exists as a sealed “bubble” of life locked below the surface of the Earth. Inspite of being totally sealed and being devoid of light, the Cave is a thriving ecosystem filled with all manner of life, from tiny crustacea to isopods, molluscs and arachnids. On the rest of the planet, ecosystems are supported by primary producers, such as plants or algae, that convert carbon dioxide from the air into living matter that can be eaten by higher organisms – this process is driven by light and is known as photosynthesis. In the dark reaches of Movile Cave, the primary producers are bacteria that convert carbon dioxide into living matter in the form of vast floating “mats” on the surface of the Cave waters. Primary production in the dark is driven by chemical energy obtain by the bacteria from the oxidation of sulfur compounds and ammonia in the Cave waters – a process called chemosynthesis. In addition to this, we believe that a proportion of bacteria in these floating mats form their biomass by consumption of methane found in the geological gases that flow through the Cave – a process known as methanotrophy.