Bacteria that use CO2 as a sole source of carbon for growth are known as autotrophic bacteria. They are capable of carbon fixation, meaning they can convert inorganic carbon (usually in the form of carbon dioxide) into organic compounds through processes like photosynthesis or chemosynthesis.

On the other hand, bacteria that use organic chemicals as a source of carbon are known as heterotrophic bacteria. These bacteria cannot fix carbon from inorganic sources and rely on pre-formed organic compounds as their carbon source. They obtain energy by breaking down these organic molecules through processes like fermentation, respiration, or other metabolic pathways.

In summary:

• Autotrophic bacteria use CO2 as a sole source of carbon and can perform carbon fixation.
• Heterotrophic bacteria use organic chemicals as a source of carbon and cannot perform carbon fixation.

Dr Gaurav H Tandon thank you for your contribution to the discussion

Autotrophic bacteria synthesize all their cell constituents using carbon dioxide as the carbon source. Chemoautotrophs: microbes that oxidize inorganic chemical substances as sources of energy and carbon dioxide as the main source of carbon. Capnophiles are microorganisms that thrive in the presence of high concentrations of carbon dioxide. Photoautotrophs are cells that capture light energy, and use carbon dioxide as their carbon source. There are many photoautotrophic prokaryotes, which include cyanobacteria. The transportation sector accounts for largest share of U.S. energy-related CO2 emissions. Consumption of fossil fuels accounts for most of the CO2 emissions of the major energy consuming sectors: commercial, industrial, residential, transportation, and electric power. Many Bacteria are chemoheterotrophs, and must consume organic molecules for both a source of carbon and of energy. Many other Bacteria are photoautotrophs, and can derive energy from light and synthesize organic compounds from carbon dioxide. Organisms that derive their energy from chemosynthesis rather than photosynthesis are called chemoheterotrophs. They extract their energy and carbon from chemical substances. Examples of chemoheterotrophs are fungi and most animals. These organisms use organic chemicals as their energy source. Most microorganisms using light as their principal source of energy are photoautotrophs, that is, they use an inorganic reduced compound as an electron donor and CO2 as a carbon source. Autotrophic bacteria synthesize all their cell constituents using carbon dioxide as the carbon source. The most common pathways for synthesizing organic compounds from carbon dioxide are the reductive pentose phosphate (Calvin) cycle, the reductive tricarboxylic acid cycle, and the acetyl-CoA pathway.