GeneBites

New research has revealed the use of a purple bacteria, R. sulfidophilum, for the production of spider silk. Researchers were able to accomplish this, for the first time ever, by using seawater as the cultivation medium. Hence, this bacteria can present a sustainable alternative to other resource-heavy organisms used in the artificial production of spider silk and signifies a positive step in the direction of sustainability.

What if I told you that plants and bacteria can be genetically modified to produce the web material spiders produce? Sounds like something out of a science fiction book, right? More importantly, why would anyone want a creation like that?

Well, like they say, reality is stranger than fiction.

Spider silk is the technical name for the web material produced by spiders, and is actually one of the strongest known biomaterials. Spiders actually make four different types of silk for various purposes. One of these is called “dragline silk”, called so because spiders use it to escape predators by dragging themselves away with it (like Spiderman!). Also called “MA silk” because it is made in the major ampullate (MA) gland of spiders, this silk has properties of high tensile strength, high extensibility, and low weight which make it attractive for human use particularly in biomedicine like in surgical stitches, wound healing, and tissue engineering. 

However, harvesting spider silk on a large scale is both difficult and complex, influenced by factors like the pH conditions needed for optimal extraction. While synthesizing spider silk in a lab is an active area of research, a more straightforward solution is to just modify some plant cells to make them produce the silk, and then process and purify it at a later point. This process, however, comes with its own challenges, like low yields and a lack of environmental sustainability. This is where genetically modified bacteria come in. 

In a recent Nature study, scientists genetically modified a marine photosynthetic purple bacterium, Rhodovulum sulfidophilum, to produce spider silk proteins. Important to note here is that spider silk is largely composed of proteins known as “spidroins” (a combination of the words spider and fibroin!) and the dragline kind that we are concerned with expresses a protein called MaSp-1.

So, how did scientists make it? First, they used a carrier to carry the spider silk gene into the bacterial cell. This carrier was modified with a few key things to ensure that the cell could be monitored for successful completion of modification. This included optimizing the gene itself to work well in bacteria and selecting markers for antibiotic and tellurite resistance as positive indicators that the bacterial cell has successfully implanted the MaSP-1 gene via bacterial exchange of genetic material.

The study examined two distinct growth conditions for the microorganisms to see how the successfully transformed bacteria were able to make spider silk proteins in different environments. The “standard” condition involved the use of light exposure and marine broth, a nutrient-rich solution derived from seawater that supports microbial growth. In contrast, the “novel” condition used a mixture of bicarbonate salt, nitrogen gas, seawater, and light. This second condition, referred to by the authors as a “photoautotrophic growth condition”, is a significant breakthrough in that it is the first report of the production of spider silk proteins using a photosynthetic and halophilic (literally salt-loving) bacterium under seawater conditions. 

These novel conditions demonstrate the use of renewable and eco-friendly resources such as seawater, offering a more sustainable alternative that addresses ongoing concerns about sustainability by reducing reliance on traditional, less eco-friendly resources. The fact that scientists were able to efficiently demonstrate successful spider silk production using these bacteria is a major achievement and holds great promise for the future of biomaterials in research.

Someday, in the not-too-distant future, your injuries might be healing with bacterially-produced spider silk. Maybe the future from science fiction books is around the corner after all?

Edited by Sarah Lester and Jayati Sharma