The nitrogen - eaters belong to two families
of photosynthetic cyanobacteria and a distantly related proteobacteria group, the researchers report in the 9 August issue of Nature.
Not exact matches
But with our planet as their guide, astrobiologists are forced to acknowledge that oxygen may be the least likely thing they will ever see — genetic evidence suggests the complex oxygen - producing
photosynthetic pathway pioneered by
cyanobacteria is an extraordinary evolutionary innovation that only appeared once throughout the entire multi-billion-year history
of Earth's biosphere.
«This is probably because
cyanobacteria are naturally
photosynthetic — they're actually responsible for a large fraction
of the photosynthesis in the ocean — and so whether the cell is energized or not is a good indication
of whether it's day or night,» he says.
To remedy that absence, Golden's lab, along with plant physiologist Takao Kondo and colleagues at Nagoya University in Japan, developed an easy - to - read gauge
of changing
photosynthetic activity in colonies
of the
cyanobacterium Synechococcus, a blue - green alga whose one - celled organisms divide as often as once every 5 to 6 hours.
The team presents new isotopic data showing that a burst
of oxygen production by
photosynthetic cyanobacteria temporarily increased oxygen concentrations in Earth's atmosphere.
On the other hand, many anaerobic microbes including methanogens are easily poisoned by oxygen, and the recent discovery
of banded sediments with rusted iron on Akilia Island in West Greenland suggests that oxygen - producing,
photosynthetic microbes (e.g.,
cyanobacteria) living on the surface
of wet areas to gather sunlight may have developed by the end
of this geologic period (3.85 billion years ago) despite continuing bombardment from space.
Many
of these microbes persist today; for example, blue - green (
cyanobacteria) or bright green,
photosynthetic bacteria use light from the Sun and chlorophyll to convert carbon dioxide and water into «free» molecular oxygen and carbon, made into essential organic substances such as carbohydrates.
Cyanosite — NASA image
of Chroococcidiopsis Dividing Chroococcus sp., a type
of cyanobacteria,
photosynthetic microbes that also produce oxygen.
Given at least nine meters (roughly 30 feet)
of water on the planet,
photosynthetic microbes (including mats
of algae,
cyanobacteria, and other
photosynthetic bacteria) and plant - like protoctists (such as floating seaweed or kelp forests attached to the seafloor) could be protected from «planet - scalding» ultraviolet flares produced by young red dwarf stars, according to Victoria Meadows
of Caltech, principal investigator at the NASA Astrobiology Institute's Virtual Planetary Laboratory.
As proposed by Andrew Goldsworthy in 1987,
cyanobacteria and later chloroplast - related protists and plants developed after microbes that used a purple pigment bacteriorhodopsin that absorbs green light dominated the oceans, and so the new
photosynthetic cyanobacteria were forced to use the left - over light with chlorophyll that reflects green light, which was too complex to change even after purple - reflecting
photosynthetic lifeforms were no longer dominant (Debora MacKenzie, New Scientist, September 10, 2010 — more on the evolution
of photosynthetic life and plants on Earth).
Endosymbiotic theory posits a later parallel origin
of the chloroplasts; a cell ate a
photosynthetic cyanobacterium and failed to digest it.
Regardless
of when the
cyanobacteria appeared, it is widely accepted that they comprised the predominant form
of life on early earth for some two billion years, and were responsible for the creation
of earth's atmospheric oxygen, consuming CO2 and releasing O2 by
photosynthetic metabolism.
Objective: To understand the first steps in the evolution
of photosynthetic eukaryotes and the impact plastidial endosymbioses (involving
cyanobacteria or unicellular algae) had on the genomes
of these organisms that are critical to the functioning
of ecosystems.
It does contain a modicum
of truth, however, in that the largest volume
of stromatolitic formations was likely formed by biogenic processes involving
photosynthetic cyanobacteria.
However, the Earth harbors a greater diversity
of photosynthetic organisms than vascular plants, and includes algae,
cyanobacteria, and anoxygenic
photosynthetic bacteria, all
of which occur in a wide array
of colors, due to adaptation and acclimation to different light and chemical environments.