Science and Technology

The tardigrade way

Team Quantum | Updated on July 04, 2021

Learning to store engineered bacteria at room temperature

What with the challenges of transporting and preserving Covid-19 vaccines, the world is now familiar with the need for refrigeration to preserve biological products. But can we do it at room temperature?

A group of scientists at Tsinghua University, Beijing, looked to Nature for clues.

Tardigrades, the tiny, one-millimetre-sized ‘water bears’, known to live in extremely harsh conditions such as boiling water, extreme heat or freezing ice, seemed to tell the scientists, “Learn from us”.

The Chinese scientists, Yixian Yang et al, inquired into how tardigrades survive desiccation. In 2017, an American molecular biologist, Thomas Boothby, of the University of North Carolina, had found out that tardigrades use a substance called ‘tardigrade intrinsically disordered proteins’ (TDP) to protect themselves from desiccation. Other organisms typically use a sugar called ‘trehalose’ for this purpose, but, of course, they can’t tolerate stresses like the tardigrades do.

The researchers worked on using TDPs to preserve other organisms, particularly engineered bacteria. They found out that it was possible. Since DNA molecules are responsible for producing proteins, one can inject a certain DNA of an organism into the cell of another, so that the same protein is produced, or “expressed”, in the host organism.

The scientists expressed the TDPs in E. coli, a bacteria that lives in the gut of human beings and is often used in biotechnology research, as they have the ability to store foreign DNA.

Then they removed moisture from the bacteria through lyophilisation — “the process of isolating a solid substance from a solution by freezing the solution and vaporising the ice away under vacuum conditions”.

The work of the scientists has been presented in a pre-print (yet to be peer-reviewed) scientific paper.

For this research, they used a bacteria called ‘pET28a’ as the vector, to transmit the TDP-producing DNA from tardigrades into the E. coli.

Preservation methods for bacteria, like the paraffin method, are not suitable for engineered bacteria, the paper notes. It also requires trained staff. “By contrast, lyophilisation is a viable option for room temperature preservation,” it says.

“However, although lyophilisation can preserve substances in the form of a powder that can be stored at room temperature, research has shown that the survival rate of lyophilised bacteria is less than 10 per cent,” it says.

The solution is to use TDPs to protect the bacteria. The study indicates that TDPs can protect E. coli strains under conditions of lyophilisation and allow the bacteria to subsequently be preserved at room temperature.

This method, when perfected, will allow longer preservation of pharmaceuticals, crops, vaccines and other products that are based on engineered bacteria and require long-distance transportation or long-term storage, without refrigeration.

The researchers note that the use of TDPs to improve the survival rates of cells under lyophilisation is “a very innovative concept”; more research is needed to perfect the method. For example, future researchers could use better vectors than pET28a.

Published on July 04, 2021

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