Arizona State University researchers make breakthrough on breaking down xylose

July 3, 2017 |

In Arizona, researchers at Arizona State University wanted to squeeze out more energy from xylose sugars. To do so, they challenged E. coli bacteria that could thrive comfortably on glucose — and switch out the growth medium broth to grow solely on xylose. The bacteria would be forced to adapt to the new food supply or lose the growth competition.

They started with a single colony of bacteria that were genetically identical and ran three separate evolution experiments with xylose. At first, the bacteria grew very slowly. But remarkable, in no more than 150 generations, the bacteria adapted and, eventually, learned to thrive in the xylose broth.

Next, they isolated the DNA from the bacteria and used next-generation DNA sequencing technology to examine the changes within the bacteria genomes. When they read out the DNA data, they could identify the telltale signs of evolution in action, mutations.

The bacteria, when challenged, randomly mutated their DNA until it could adapt to the new conditions. They held on to the fittest mutations over generations until they became fixed beneficial mutations.

And in each case, when challenged with xylose, the bacteria could grow well. Their next task was to find out what these beneficial mutations were and how did they work. To grow better on xylose, the three bacterial E. coli lines had “discovered” a different set of mutations to the same genes. The single mutations the research team identified all could enhance xylose fermentation by changing bacterial sugar metabolism.

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Category: Research

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