Researchers supported in part by the NASA Exobiology Program have documented the production of extracelluar superoxides from five groups of marine organisms that represent some of the most abundant microbial populations in Earth’s oceans. Superoxide is an anion radical that is made by removing one electron from molecular oxygen. Superoxides are produced by bacteria and eukaryotes, and are often associated with oxidative stress. However, superoxide is also used by cells for essential processes like growth and defense.

Many organisms in the oceans produce superoxide outside of their cells. A new study is helping scientists understand how this production affects the ecology of Earth’s oceans. The team looked at organisms that release superoxide in the absence of light across five different groups that are spread around the globe. The findings suggest that superoxide production in both sunlit and dark ocean water is regulated by a diverse suite of marine organisms. Production of extracellular superoxide was inversely related to cell number, and the researchers believe that this might indicate that superoxide plays an role in cell signaling.

The study, “Extracellular superoxide production by key microbes in the global ocean,” was published in the journal Limnology and Oceanography. The work was supported in part by NASA Astrobiology through the Exobiology Program.