Chemoautotrophic bacteria are bacteria that obtain their energy from the oxidation of inorganic substances and use carbon dioxide as their sole carbon source. They are typically found in environments such as deep-sea hydrothermal vents, hot springs, and caves where they can utilize the energy from chemical reactions to survive. Examples of chemoautotrophic bacteria include Nitrosomonas, Nitrobacter, and Thiobacillus. Nitrosomonas and Nitrobacter are involved in the nitrogen cycle, while Thiobacillus is known for its ability to oxidize sulfur compounds.