Tuesday, March 20, 2012

Technique turns yeast into little machines

We have many small organisms working for us. Among others, we have employed bacteria to produce various substances, such as insulin for diabetes patients. They can also be used as sensors to detect changes in the environment. Because we have the capability to modify microbes genetically, we can turn them into a lot of things that are useful for us. Scientists from the Imperial College London have found a way to greatly expand the possibilities to employ another small worker: yeast. A technique involving genetic engineering developed by the British turns them into small machines.

Scientists are interested in yeast because of their similarity in physiological processes when compared to humans. Therefore, they are often used to discover how things work, such as how to increase our life span, which we can then apply to ourselves. In addition, researchers think yeast is also quite suitable for synthetic biology, which is basically turning organisms or biological principles into little machines. So far, using yeast as a machine has been limited in success, mainly due to a lack of suitable engineering tools. However, the aforementioned new form of genetic engineering renders us able to modify yeast by deploying things similar to circuits found in electronic devices.
Yeast (S. cerevisiae) in its natural shape
This form of genetic engineering is not new, but has always been limited because we lacked technical ability to makes these circuits complex enough. Yeast contains a protein called Talor which seems to have properties similar to those found in small wires used for electric circuits. Because the scientists have proven capable of re-engineering these proteins at will, they were able to create a library of tools suitable for building biological circuits needed to turn yeast into a machine that does our bidding. The wire shape is mimicked by DNA: Talor is able to bind to the genetic code and thereby create a seemingly endless number of cross-links, adding to the complexity of biological circuits.

Our DNA contains several structures that initiate transcription, or read-out, of genes. These so-called promoters basically control gene expression inside a cell because they can turn it on and off. At the Imperial College London, a specific promoter was used to assert control over the biological circuit in yeast cells. They used this promoter to create a library of derivatives that aid in the reprogramming process. By creating a whole set, they have made it easier to turn yeast into machines with a wide variety of useful features.

Scientists reckon the Talor proteins combined with DNA structures enable complex biological wiring of yeast, which in turn allows us to highly customize their characteristics and functions. Examples include using yeast as sensors for various substances: they could monitor the environment by keeping a proverbial eye on toxins and warning us, for example, by changing colour. Additionally, increased ease in modifying yeast may increase the options we have to let them produce useful substances, such as drugs. 

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