Marine organism bypasses photosynthesis for survival

March 13th, 2008 - 11:23 am ICT by admin  


Washington, March 13 (IANS) Some marine organisms are able to get much of their energy bypassing photosynthesis - the most vital biological process on earth, responsible for all our food. Two recent studies by Carnegie Institution scientists suggest that these micro-organisms neither release oxygen nor take in carbon dioxide.

If true, this discovery impacts not only our basic understanding of photosynthesis, but also how micro-organisms in oceans affect rising levels of atmospheric carbon dioxide, Sciencedaily reported.

Led by Arthur Grossman, the scientists investigated photosynthesis in marine Synechococcus, a form of photosynthetic bacteria called cyanobacteria and better known as blue-green algae.

These single-celled organisms dominate phytoplankton populations over much of the world’s oceans and are important contributors to global primary oxygen productivity.

Grossman and his colleagues wanted to understand how Synechococcus could thrive in iron-poor water that cover much of the ocean, since certain activities of normal photosynthesis require high levels of iron.

“It seems that Synechococcus in the oligotrophic oceans has solved the iron problem, at least in part, by short-circuiting the standard photosynthetic process,” said Grossman.

“Much of the time this organism bypasses stages in photosynthesis that require the most iron. As it turns out, these are also the stages in which carbon dioxide is taken from the atmosphere.”

“The uptake of carbon dioxide and the photosynthetic activities didn’t match, so we knew that something other than carbon dioxide was being consumed by photosynthesis, and it turned out to be oxygen,” said Grossman’s colleague Shaun Bailey.

“This discovery represents a paradigm shift in our view of photosynthesis by organisms in the vast, nutrient-starved areas of the open ocean,” said Joe Berry of Carnegie.

“We had assumed that like higher plants, the goal was to make carbohydrates from carbon dioxide and store them for later use as a source of energy for any number of cellular functions or growth.

But it is now clear that some organisms short-circuit this process, using light in a minimalist way to power cellular processes directly.

Scientists still are not clear about the full significance of this finding, but it is certain to change the way optical measurements of photosynthetic pigments in the ocean are interpreted and how ocean productivity is measured.

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