Two types of respiration is found in bacteria. They are:

1. Aerobic respiration 

2. Anaerobic respiration

1. Aerobic respiration: These bacteria require oxygen as terminal acceptor and will not grow under anaerobic conditions (i.e. in the absence of O ) 

Example: Streptococcus.

(i) Obligate aerobes: Some Micrococcus species are obligate aerobes (i.e. they must have 1 oxygen to survive).

2. Anaerobic respiration: These bacteria do not use oxygen for growth and metabolism but obtain their energy from fermentation reactions. 

Example: Clostridium.

(i) Facultative anaerobes: There are bacteria that can grow either using oxygen as a terminal electron acceptor or anaerobically using fermentation reaction to obtain energy. When a facultative anaerobe such as E. coli is present at a site of infection like an abdominal abscess, it can rapidly consume all available O and change to anaerobic metabolism producing an anaerobic environment and thus allow the anaerobic bacteria that are present to grow and cause disease. 

Example: Escherichia coli and Salmonella.

(ii) Capnophilic bacteria: Bacteria which require CO₂ for their growth are called as capnophilic bacteria. 

Example: Campylobacter.