Examples include Clostridium, Bacteroides, Fusobacterium, and Actinomyces israelii.

They lack catalase and/or superoxide dismutase and are thus susceptible to oxidative damage.

Generally foul smelling (short-chain fatty acids), are difficult to culture, and produce gas in tissue (CO₂ and H₂).

Anaerobes are normal flora in GI tract, typically pathogenic elsewhere.

Aminoglycosides are ineffective against anaerobes because these antibiotics require O₂ to enter into bacterial cell.