Definition

• Bacterial respiration is the extraction of energy from glucose to convert that energy into forms the bacteria can use, according to Jacquelyn G. Black, Ph.D.
  
  

Free Oxygen

• Using free oxygen (O2), bacteria can fully exploit all three chemical pathways for energy extraction--glycolysis, the Krebs Cycle and the electron transport chain, notes the book "Microbiology."
  
  

Oxygen Compounds

• In the absence of O2, some bacteria can still use oxygen by getting it from inorganic oxygen-containing molecules, such as nitrate, nitrite and sulfate, notes Jacquelyn G. Black, Ph.D.
  
  

No Oxygen

• Alternatively, fermentation enables some bacteria to derive energy from glucose without using oxygen of any kind, notes Alvin Fox, Ph.D. of the University of South Carolina School of Medicine.
  
  

Comparisons

• Respiration using oxygen (aerobic respiration) provides bacteria with as much as 19 times more energy per glucose molecule than does fermentation, notes the book "Biology." Generally, the more of the electron transport chain respiration uses, the more energy it provides, according to the book "Microbiology."