Daily Newsletter February 24, 2012

Daily Newsletter February 24, 2012

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Evolution Friday

In the bacteria, there are organisms defined as chemolithoautotrophs. Chemolithotrophs are organisms that gain reducing power from reduced inorganic compounds, like iron. Since bacterial respiratory chains are located on the cellular membrane (no mitochondria), they can interact with reduced compounds in the environment. Being an autotroph means that you can fix your own carbon (we will see this next week). Carbon fixation means that you take CO₂ and reduce it to an organic carbon compound.

Bacterial respiratory chains are different than mitochondrial respiratory chains. In the mitochondria, you will find an ubiquinone between complex I and III that serves as an electron carrier (moving between complex I and III). In bacteria, you find a pool of quinones (ubiquinone is only one type of quinone). It is this quinone pool that allows chemolithotrophs to harvest reducing potential from reduced inorganic compounds.

The autotrophic aspect of these organisms is different from eukaryotic autotrophs (plants and algae). Some of these bacteria use what is called a reverse (reductive) TCA, or reverse citric acid cycle.

Bacteria in the Chlamydomonas, Proteobacteria groups are generally known to do this reaction. Some of these organisms can carry out these reactions without the presence of oxygen. (Why would the organism not need oxygen?  Why would that be important?)

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Daily Challenge:
A strong evolutionary theory states that these organisms were present before organisms that show the process of photosynthesis as we see in plants. Explain why you might find these organisms before the forms of carbon fixation we see now (i.e., plants).