Biofuel research given a boost by cyanobacteria

Cyanobacteria are found in almost every aquatic and terrestrial habitat. Image: Shutterstock

The discovery of how cyanobacteria really produce energy is expected to help scientists manufacture biofuels.

In 1967, two groups of researchers scientists concluded that cyanobacteria lacked the ability to make one enzyme, causing their energy-making cycle to be incomplete. This energy-producing cycle ““ also known as the tricarboxylic acid (TCA) cycle or the Krebs cycle- includes a series of chemical reactions that are used for metabolism by most forms of life, including bacteria, molds, protozoa and animals.

This 44-year-old assumption has been shown to be incorrect by a team of scientists, led by Donald Bryant from Penn State. “During studies 44 years ago, researchers concluded that cyanobacteria were missing an essential enzyme of the metabolic pathway that is found in most other life forms,” he said.

“As it turns out, the researchers just weren’t looking hard enough, so there was more work to be done.”

The 1967 assumption was never corrected and was later confirmed by scientists using modern genome-annotation methods. Bryant suggested that these methods were partly to blame. “Computer algorithms are used to search for strings of genetic code to identify genes.

“Sometimes important genes simply can be missed because of matching errors, which occur when very similar genes have very different functions. So if researchers don’t use biochemical methods to validate computer-identified gene functions, they run the risk of making premature and often incorrect conclusions about what’s there and what’s not there.”

Bryant and his team tested the hypothesis by running new biochemical and genetic analyses on a cyanobacterium called Synechococcus sp. PCC 7002. Synechococcus had genes that coded for an alternative enzyme, succinic semialdehyde dehydrogenase, which was adjacent to a misidentified gene that coded for 2-oxo-glutarate decarboxylase.

These two enzymes work together to complete the TCA cycle in a different way. The researchers also said that the genes are present in most cyanobacteria genomes, with the exception of a few marine species.

The findings from this research could be used to investigate new ways of producing biofuels. “Now that we understand better how cyanobacteria make energy, it might be possible to genetically engineer a cyanobacterial strain to synthesize 1,4-butanediol — an organic compound that is the precursor for making not just biofuels but also plastics,” Bryant said.

Source: Penn State

More information about biofuel production can be found in the January/February issue of Science Illustrated Australia, on sale from January 18.

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