New theory suggests certain marine microorganisms do not require photosynthesis

March 12th, 2008 - 3:06 pm ICT by admin  

Washington, March 12 (ANI): A new study has suggested that certain marine microorganisms do not require photosynthesis, which is the most important biological process on Earth.

Photosynthesis by plants, algae, and some bacteria supports nearly all living things by producing food from sunlight, and in the process these organisms release oxygen and absorb carbon dioxide.

But, a study conducted by scientists at the Carnegie Institution in US, has suggested that certain marine microorganisms have evolved a way to break the rulesthey get a significant proportion of their energy without a net release of oxygen or uptake of carbon dioxide.

This discovery impacts not only scientists basic understanding of photosynthesis, but importantly, it may also impact how microorganisms in the oceans affect rising levels of atmospheric carbon dioxide.

For the study, the research team, led by Arthur Grossman from the Carnegie Institution, investigated photosynthesis in a marine Synechococcus, a form of photosynthetic bacteria called cyanobacteria.

These single-celled organisms dominate phytoplankton populations over much of the worlds oceans and are important contributors to global primary productivity. Grossman and his colleagues wanted to understand how Synechococcus could thrive in the iron-poor waters that cover large areas of the ocean, since certain activities of normal photosynthesis require high levels of iron.

While others had suggested a potential role of oxygen as accepting electrons from the photosynthetic apparatus in place of carbon dioxide, the studies by Grossmans group show that this activity is significant in the oligotrophic (nutrient-poor) oceans, which cover about half the oceans area.

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, he added.

According to Shaun Bailey, the lead postdoctoral fellow working on this project, The uptake of carbon dioxide and the photosynthetic activities didnt match, so we knew that something other than carbon dioxide was being consumed by photosynthesis, and it turned out to be oxygen.

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 the Carnegie Institutions Department of Global Ecology.

We now know that some organisms short-circuit this complicated process, using light in a minimalist way to power cellular processes directly with a far simpler and cheaper photosynthetic apparatus, he added.

According to Berry, We don’t know the full significance of this finding yet, but it is certain to change the way we interpret optical measurements of photosynthetic pigments in the ocean and the way we model ocean productivity. (ANI)

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