Major nutritional types of prokaryotes
| Nutritional type | Energy source | Carbon source | Example |
| Photoautotrophs | Light | CO2 | Cyanobacteria, purple non-sulfur bacteria, purple sulfur bacteria, and green sulfur bacteria |
| Photoheterotrophs | Light | Organic compounds | Non-purple sulfur bacteria and purple sulfur bacteria |
| Chemoheterotrophs (or chemoorganotrophs or simply heterotrophs | Organic compounds | Organic compounds | Most Bacteria and some Archaea |
| Chemolithotrophs (or chemoautotrophsA) | Reduced inorganic compounds (e.g., H2, NH3, H2S, Fe+2 or elemental sulfur as well as other sources) | CO2 | Few Bacteria and many Archaea |
A - these are referred to primarily as chemolithotrophs to emphasize their ability to oxidize reduced inorganic compounds to generate ATP.
Consider how or where do these nutritional types get their reducing equivalents (i.e., NADH or NADPH)????
