Stephen Kintz
Dec 18, 2011

Cyanobacteria: Our oxygen, the TCA cycle, and how blue-green algae promises biofuel

Cyanobacteria (a.k.a blue-green algae) are a very important phylum of bacteria. Scientists believe that the bacteria are responsible for helping to create the oxygen rich atmosphere, which led to the extinction of almost all oxygen-intolerant organisms and would, eventually, lead to us.


It is responsible for around 20 percent of the world’s total photosynthesis productivity, and it has the very prestigious honor of being one of the first photosynthetic organisms to have its genome completely sequenced. Yet, our ability to use cyanobacteria for our benefit might be limited by our misconceived knowledge of the bacteria.


Researchers Shuyi Zang and Donald A. Bryant have published an article in “Science” on December 16, 2011 that claims our basic understanding of cyanobacteria’s tricarboxylic acid (TCA) cycle has been wrong for almost 4 decades. The TCA cycle is a series of chemical reactions used by aerobic organisms to generate energy from carbohydrates, fats and proteins. In 1967, researchers concluded the cyanobacteria did not possess the enzyme 2-oxoglutarate-dehydrogenase, which produces an important compound to the TCA cycle. The lack of this enzyme meant that cyanobacteria could not take part in, or gain from, much of the TCA cycle.


Shuyi Zang and Donald A. Bryant knew that many organisms, like Mycobacterium, complete the TCA cycle through alternative methods, so the researchers re-analyzed the genetic data on cyanobacteria and discovered two important genes that code for the enzymes succinic semialdehyde dehydrogenase and 2-oxoglutarate decarboxylase. As it turns out, 44 years of assumed knowledge was overturned; these enzymes are used to complete the TCA cycle [The Tricarboxylic Acide Cycle in Cyanobacteria].


This is an important discovery because it demonstrates that our genetic knowledge and metabolic understanding of the bacteria were incomplete. With a more complete picture of the genetic structure and compounds within cyanobacteria, scientists should be better able to genetically alter the bacteria for useful means. In fact, Shuyi Zang and Donald A. Bryant hope that the bacteria can be genetically altered to produce bio-fuels and, maybe plastics.


While the researchers did not mention how they plan to use the knowledge to create bio-fuels, other researchers at Joule Ultimate have already genetically altered and patented cyanobacteria that is able to produce the diesel fuel molecule, n-alkenes [Joule wins key patent for GMO cyanobacteria that create fuels from sunlight, CO2 and water]. Presumably, the research by Shuyi Zang and Donald A. Bryant might lead to more productive cyanobacteria.


More importantly, the research into genetically alternating cynaobacteria is promising not just because of the research above. No. Bio-fuels from blue-green algae are promising because they can produce the molecules directly from CO2 and sunlight.


The bacteria is also easy to grow and easy to achieve high biomass with in a relatively small amount of time. This is compounded further with the knowledge that cyanobacteria require little nutrients and do not need to waste arable land that could be better used to produce food. Cyanobacteria are also extremely hardy. The bacteria can survive in a wide range of climates and ph conditions.


Of course, there have been many scientific discoveries and new technologies that are foretold to change society and save us from doom, but after a short while, they disappear or peter out. This might be one of the best advantages to cyanobacteria, and why it might be the most promising future-tech fuel currently available. Researchers, corporations and governments are interested in this research. Arizona State University is beginning to create a laboratory sized bio-fuel production center [Cyanobacteria Biodiesel: Tubes in the Desert]. This is to test the feasibility of cyanobacteria as a source of bio-fuel. It appears that people are interested, which might be the most important factor in its future.


So, I will probably be keeping an eye out for future developments in cyanobacteria. I think that you might want to too.