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The remaining bacteria listed do not form endospores. [5] Several species of the Mycobacterium, Streptomyces, and Rhodococcus genera are examples of obligate anaerobe found in soil. [10] Obligate anaerobes are also found in the digestive tracts of humans and other animals as well as in the first stomach of ruminants. [11]
[5] [6] Two examples of obligate anaerobes are Clostridium botulinum and the bacteria which live near hydrothermal vents on the deep-sea ocean floor. Aerotolerant organisms, which cannot use oxygen for growth, but tolerate its presence. [7] Facultative anaerobes, which can grow without oxygen but use oxygen if it is present. [7]
A unique obligate aerobe is Streptomyces coelicolor which is gram-positive, soil-dwelling, and belongs to the phylum Actinomycetota. [7] It is unique because the genome of this obligate aerobe encodes numerous enzymes with functions that are usually attributed to anaerobic metabolism in facultatively and strictly anaerobic bacteria. [7]
Bacteroides is a genus of Gram-negative, obligate anaerobic bacteria. Bacteroides species are non endospore–forming bacilli, and may be either motile or nonmotile, depending on the species. [3] The DNA base composition is 40–48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids.
Anaerobic bacteria can be divided into strict anaerobes that can not grow in the presence of more than 0.5% oxygen and moderate anaerobic bacteria that are able of growing between 2 and 8% oxygen. [1] Anaerobic bacteria usually do not possess catalase, but some can generate superoxide dismutase which protects them from oxygen.
A facultative anaerobic organism is an organism that makes ATP by aerobic respiration if oxygen is present, but is capable of switching to fermentation if oxygen is absent. [1] [2] Some examples of facultatively anaerobic bacteria are Staphylococcus spp., [3] Escherichia coli, Salmonella, Listeria spp., [4] Shewanella oneidensis and Yersinia ...
Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube. A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than that are present in the atmosphere (i.e. < 21% O 2 ; typically 2–10% O 2 ) for optimal growth. [ 1 ]
Anaerobic bacteria can be identified by growing them in test tubes of thioglycollate broth: 1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.