New Species

A new species of giant sulfur bacteria found the in the Southeast Pacific Ocean may provide insight into early forms of life on earth and could provide a potential model for the search for extraterrestrial life.

It has been hypothesized in recent decades that the study of organisms from light and oxygen deficient environments could provide insight into the evolutionary history of early life on Earth. Ancient seas, almost universally accepted as the cradle of life on Earth, were highly deficient in oxygen and lacked the same light regimes that we observe on Earth today. Thus, it is proposed that early life was likely chemoautotrophic, much like the organisms found in hydrothermal vent communities today. A new community of giant chemoautotrophic sulfur bacteria found in the Southeast Pacific Ocean may provide further information for scientists seeking to answer questions regarding the evolution of life on this planet, and perhaps life on other planets.

First observed in 2004, communities of large, filamentous bacteria have been collected at numerous sites in the Southeastern Pacific Ocean including from oxygen deficient continental shelf sediments along the north and central coast of Chile, from a muddy beach near a mangrove swamp in Panama, and in the organically rich sediments beneath a salmon aquaculture pen in southern Chile. All of these sites are characterized by high levels of hydrogen-sulfide and low levels of oxygen. This fact, coupled together with the presence of sulfide particles inside the cells, is suggestive of sulfide-based chemosysthesis. These communities likely play an important role in the trophic web of the ecosystem where they are present by contributing to overall productivity. The extent of this role and the importance of these communities to the health of the larger ecosystem has yet to be determined. These questions and other raised by the discovery of this community will provide research avenues for the future.

Another interesting fact about these giant bacteria is that their large filamentous morphology as well as their multicellular nature is similar to fossils of early life on Earth. These fossils were previously described as photosynthetic cyanobacteria, but may now have to be re-examined in light of this new Census of Marine Life discovery. The fact that the dating of the fossils did not match the emergence of an oxygen rich atmosphere in Earth's history suggests that they may actually be fossils of chemosynthetic bacteria, similar to those that make up this newly discovered community.

Because these bacteria do not require either light or oxygen, they may be related to potential extraterrestrial life forms. Thus, not only could these bacteria provide insight into the origins of life on Earth, but they could also provide new information for astrobiologists in the search for life on other planets.

What: Discovery of a new giant species of sulfur bacteria
Who: ICoMM Scientists --> V.A. Gallardo and C. Espinoza
When: March 2004
Where: Off the north and central coast of Chile, central and northern Peru, Galapagos Islands, Pacific coast of Panama, and Costa Rica
How: Collected by monocorer, multicorer, box corer, and grab
Reference: Gallardo, V.A. and C. Espinoza, 2007. New communities of large filamentous sulfur bacteria in the eastern South Pacific. International Microbiology (2007) 10: 97-102.

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