Oxygen is prevalent in the atmosphere as gaseous diatomic oxygen (O₂), in the hydrosphere as water (H₂O), and the geosphere as oxides of various metal and metalloid elements. Oxygen is prevalent in biological molecules and commercial compounds. Examples of the latter include phenol, n-octanol, methylethylketone, and methyl-t-butyl-ether (MTBE).

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Baumgarten A, Redenius I, Kranczoch J, Cypionka H. Periplasmic oxygen reduction by Desulfovibrio species. Arch Microbiol. 2001 Oct;176(4):306-9.

Chen J, Tannahill AL, Shuler ML. Design of a system for the control of low dissolved oxygen concentrations: critical oxygen concentrations for Azotobacter vinelandii and Escherichia coli. Biotechnol Bioeng. 1985 Feb;27(2):151-5.