When it comes to using microorganisms in the biotech industry, we can say there are two main kinds of scientists: those who work with Escherichia coli in their labs, and those who prefer Bacillus subtilis. These two bacteria species can be considered as counterparts: they belong to opposed groups in the Gram classification, a test that sorts bacteria into Gram + (as B. subtilis) and Gram – (as E. coli) depending on their cell wall structure. However, both species are the best-studied bacteria of each Gram group and they have many abilities and benefits that are widely exploited in research and industry. Maybe that is why we could not decide at Rafts for Biotech and we chose to use both – and don’t blame us, this is like asking “who do you like best, Mom or Dad?”
In a previous post we already explored some of E. coli’s applications, so now let’s take a look at what B. subtilis has to offer.
The first uses of B. subtilis in science date back to the 1950s. It was used as a treatment for gut and urinary tract infections in America and Europe. Nowadays, B. subtilis has become a common tool in several chemical industries and research labs, but with a different purpose: acting as a “living factory”.
The industrial production of chemical compounds is facing an important limitation in our times: the procedures used tend to produce many pollutants. This needs to change for the market to grow sustainably and producing these chemicals inside microbes is already considered as a suitable alternative to traditional procedures. The microorganisms used for this receive the name of biofactories and, for this task, B. subtilis presents several interesting qualities: it can produce great amounts of product quickly, it is certified as safe, and it can be genetically modified very easily. In fact, while looking for the “perfect” biofactory, researchers have managed to engineer B. subtilis bacteria to remove all their genetic information that is not essential for the microbe’s survival, as we explained in a previous post. This strategy reduces interferences with the reactions the microbe needs to produce a molecule of industrial interest.
However, there are two properties that make this microbe stand out from others.
Better out than in
Generally speaking, the molecules that B. subtilis produces are pushed out of the cell into the growing medium. Once outside the bacteria, these products are way easier and cheaper to isolate, especially in large-scale processes that happen in the industry. This superior capacity for compound secretion, combined with its ability to produce great quantities of products quickly, makes B. subtilis extremely profitable as a biofactory!
Some examples of products generated using B. subtilis could be riboflavin, also known as vitamin B2, used in cosmetics, food and drugs; or amylase that can be used as a detergent. And let’s not forget our own approach in Rafts4Biotech: producing antibiotics that are toxic to the cell by taking advantage of the lipid rafts in their membrane.
Spores are a “sleeping” state of bacteria in which they have almost no vital activity. They use this skill to survive extreme environmental situations, so the organism turns into a strong resistant cocoon until their external situation improves. B. subtilis naturally forms highly resistant spores in food shortages, so they can be reverted if nutrients become available again.
Spores’ resilience and the ability of B. subtilis to swap between states makes this microbe even more versatile. Its use started in the 1960s with space experimentation, when scientists found the spores of this bacterium could survive up to six years in space if coated to protect them from UV rays. Nowadays they have expanded to many other areas. For example, in medicine, spores are used as drug “carriers”, structures which deliver compounds right where they are needed in the body. This has already been exploited in vaccines and cancer treatments. Spores also have a role in material science: they have been used as a source in 3D printing due to their resistance, or as a biological solution to preserve building materials like concrete from deteriorating.
Spores even have a role in compound production, although it is different from the active state of B. subtilis. They are used to facilitate the recovery of intermediary molecules that are used to produce others. These molecules are attached to the spores, forming a bigger structure that is easier to isolate from a mix. This way, those components can be reused for further reactions, reducing the production costs. The most relevant molecules used attached to spores are enzymes, such as lipase, used for the degradation of fats.
Although scientists have developed many applications for B. subtilis already, its full potential as a biofactory (and beyond) is yet to be exploited. That is why research continues to further understand its cellular mechanisms and to develop new microbial engineering tools. Many scientific approaches and startups are trying to exploit B. subtilis capabilities in an innovative way – as we do in Rafts for Biotech. You can find some in the news we share on this blog or in our social media. Stay tuned!