Endospore germination may occur after as many as 1,000 years of dormancy . Bacteria play a significant role in ecosystems . Some are similar to plants in that they use H2O and produce oxygen as a byproduct of photosynthesis. Others use H2S and produce sulphur as a byproduct. Chemoautotrophic bacteria oxidize gaseous nitrogen or inorganic compounds such as those containing iron, nitrogen or sulphur to derive energy which is used to fix CO2.
Heterotrophic bacteria derive energy from the breakdown of organic molecules.
They may be facultative anaerobes , obligate anaerobes or aerobes . Some use light as a source of energy. The great majority of bacteria and other life forms are heterotrophs. Nitrogen-fixing bacteria are important components of ecosystems, as they convert atmospheric N2 to a form of nitrogen which can be assimilated by plants. Bacteria play additional important roles in most biogeochemical cycles .