Bacterial Dyes in Fashion
People have used other organisms to dye clothing since prehistory. Archaeologists traced indigo derived from plants to a 6,000-year-old piece of fabric recovered on the coast of Peru. Aztec and Maya peoples extracted a crimson dye from insects on cactus and others in the Mediterranean made royal purple from snails. As I found these stories of natural dyes from all kinds of plants and animals, I found fewer examples of ancient dyes from creatures of the microbial world. There is a long record of making dyes from lichen and mushrooms, but not from the most biodiverse domain of life, the Bacteria. This is not too surprising, since we only began culturing isolated bacterial species a few hundred years ago. And the lack of history in this case is a good thing: it means that the history of using bacteria for dyeing clothing is being made right now.
Today, innovative designers like Natsai Audrey Chieza are using actinobacteria to naturally dye textiles. Actinobacteria like Streptomyces species are familiar to microbiologists as organisms that live in the soil with complex lifecycles and robust secondary metabolisms. The multitude of molecules produced by actinobacteria includes many antibiotics and other bioactive compounds, some of which double as pigments. I have worked quite a bit with Streptomyces and knew about the pigments they make. I did not, however, know that they’re being used to dye fabric. So when Natsai invited me to collaborate and photograph her recent project as a designer-in-residence at Ginkgo Bioworks, I instantly agreed.
To photograph the process in detail, we used smaller sections of various fabrics fit for Petri plates. Natsai soaked the fabric pieces in a dilute liquid culture of Streptomyces coelicolor and placed them on the surface of an agar growth medium. After a few days of incubation, colonies formed throughout the plate, both on top of the fabric and in the space between the fabric and the medium. As the colonies grew the millions of cells produced so much pigment that the color became visible to the naked eye, and to my timelapse camera. Eventually the colonies developed fuzzy aerial mycelia and in the end the fabric became like a tie-dye t-shirt, with shades of red, pink, purple and blue.
The polyketide antibiotic actinorhodin is one of the keys to the S. coelicolor dying process. Source.
Looking at the photographs, I wonder now at the biology behind the beautiful patterns. We could certainly get hard answers by chemically mapping the fabrics using advanced mass spectrometry to see which pigment molecules are where and when. In lieu of those experiments, I can speculate. The first key to the patterns is that colonies grow at different rates throughout the plate, and in some locations they do not develop at all. This is due to the texture and placement of the fabric. The bacteria on and nearest to the medium have direct access to water and nutrients and grow best. Meanwhile fewer colonies develop on crinkles of fabric raised above the media, because there the bacteria rely only on what can diffuse up into the fabric and on what nutrients were initially soaked into the fabric. The next key is the pigments themselves. Streptomyces coelicolor produces pink to red prodiginine molecules (like prodigiosin) and the water-soluble molecule actinorhodin. Actinorhodin is exported into the extracellular environment and its color depends on pH; it is blue in typical laboratory cultures. Therefore, the deep magenta of the flat sections of fabric is likely a combination of the red prodiginines which stay with the colonies and blue actinorhodin that is both in the colonies and diffuses out. And the blue color is seen in areas that lack enough cells to detect red from intracellular prodiginines while still close enough to large colonies that actinorhodin diffuses out. The colonies may also be changing the pH of their surroundings as they metabolize nutrients, creating a mosaic of microenvironments and different shades of actinorhodin in more acidic areas. No two pieces of fabric will be the same. Like the subtle flavors of a wine produced by the microbial fermentation of grapes, we don’t fully understand how the exact end product arises, and there is added beauty in that mystery.
While this bacterial dyeing process is novel and intriguing, perhaps you are curious if it has any practical purpose. After sourcing dyes from nature for millennia, the synthetic dye industry emerged in the 19th century to meet the demands of mass markets. But synthetic dyes can be toxic and they pollute the environment. So, natural dyes are coming back. However, plants that produce pigments like those used by ancient peoples require a lot of land and water and harvesting animals at scale is inefficient and detrimental to the native ecosystem. Streptomyces coelicolor on the other hand is harmless and easy to grow. One can even imagine it could be genetically tuned for maximal pigment production and scaled up with a small footprint and little impact on the environment. Someday everything from blue jeans to red scarfs may be dyed by bioengineered microbes.
A timelapse showing several days of S. coelicolor growth on fabric in 5 seconds.
- Natsai’s Chieza’s design studio Faber Futures, with photos of more of her finished fabrics
- How to make your own dyes from lichen
- Charkoudian, L.K., Fitzgerald, J.T., Khosla, C. & Champlin, A. (2010) In Living Color: Bacterial Pigments as an Untapped Resource in the Classroom and Beyond. PLOS Biology.
All photographs in this post by Scott Chimileski