Bacteria can Manufacture High-Performance Proteins, like Spider Silk, for Space Missions

Researchers developed a new technique that could produce difficult-to-make proteins, like spider silk, by taking advantage of engineered bacteria.

The mechanical properties of some of the natural, protein-based substances put them in the same bracket as the best synthetic materials. The research presented at the American Chemical Society (ACS) on 2^nd April 2019 explained that the strength and durability of spider silk are even greater than steel when similar quantities are compared. Having said that, mass production cannot be achieved with natural proteins and this is where their newly-designed method comes into play. It takes advantage of engineered bacteria to produce large quantities of spider silk and other natural proteins that could prove extremely useful for future space missions. Fuzhong Zhang, the Principal Investigator of the Project, described the mission of his research in the following words:

“In nature, there are a lot of protein-based materials that have amazing mechanical properties, but the supply of these materials is very often limited. My lab is interested in engineering microbes so that we can not only produce these materials but make them even better.”

Spider Silk

Spider silk is a difficult commodity to farm for a number of reasons. Firstly, the quantity produced by spiders is so less that you can never use this material at a massive scale. In addition to that, some of the species become cannibalistic when kept in groups. As a result, scientists were forced to look for an alternative way of producing this high-performance protein. This urged them to engineer bacteria, yeast, and plants to produce spider silk but another hurdle halted their progress. The complexity of the spider silk proteins is so much that researchers cannot replicate the mechanical properties of the natural fiber, completely.

Encoded by very long, highly repetitive sequences of DNA, spider silk proteins become extremely unstable when these genes are shifted to other organisms. In order to find a solution to that problem, Zhang and his team decided to break these lengthy sequences into shorter blocks that could be handled by bacteria. They believed that the proteins made by these tiny organisms could then be assembled into longer fibers of spider silk by the researchers.

Consequently, they introduced two pieces of encoded spider silk protein to bacteria. Each of these pieces was accompanied by a sequence of naturally occurring protein with enzymatic activity, called a Split Intein. The job of these two split intein was to join both the protein fragments and then cut themselves out to yield an intact fiber. The researching team observed that the fibers of this microbially produced spider silk had all the properties (toughness, exceptional strength, and stretchability) of the natural protein. They extracted a lot more silk with this technique than they could from spiders and are currently trying to obtain even more yield from this process.

Potential of the Protein-joining Reaction

Spider silk is one of the many materials that can be produced by this method. All the researchers need to do is to replace the DNA with another sequence and bacteria will produce the corresponding protein. For instance, scientists made a high-performance protein from mussels, which has the ability to stick strongly to surfaces. Due to this amazing property, it is believed that this material will one day be used as an underwater adhesive.

Following the success of the experiment, Zhang now wants to streamline the process so that the protein-joining reaction can occur inside bacterial cells. This will give a massive boost to the efficiency of the process because researchers won’t have to perform the rigorous purification procedure. Similarly, the overhead of incubating purified proteins will also be eliminated. The applications of this extraordinary technique are limited to our planets as it can produce helpful proteins for future space missions. That’s the reason why NASA funded this research as Zhang said,

“NASA is one of our funders, and they are interested in bioproduction. They’re currently developing technologies in which they can convert carbon dioxide into carbohydrates that could be used as food for the microbes that we’re engineering. That way, astronauts could produce these protein-based materials in space without bringing a large amount of feedstocks.”