Final answer:
Bacteria can use alternative electron acceptors such as nitrate (NO3¯), sulfate (SO42-), and carbon dioxide (CO2) in place of oxygen for anaerobic respiration, which is important for global nitrogen, sulfur, and carbon cycles.
Step-by-step explanation:
Three alternative terminal electron acceptors used by bacteria other than oxygen (O2) include:
- Nitrate (NO3¯), which is converted to nitrogen gas (N2) by denitrifying bacteria, impacting soil nitrogen availability.
- Sulfate (SO42-), which is reduced to hydrogen sulfide (H2S) by sulfur bacteria, affecting sulfur cycling and availability.
- Carbon dioxide (CO2), used by methanogens among the Archaea to produce methane (CH4), influencing carbon cycling and greenhouse gas emissions.
Bacteria that can utilize these alternative electron acceptors are involved in processes like denitrification, methanogenesis, and sulfate reduction, playing crucial roles in global biogeochemical cycles.