Revealing Bacteria’s True Colors:
Shimmering from Collective Patterns
How Bacteria Promise Sustainable Pigment-Free Colors
Genes can now predict the formation of structural color in bacteria. Scientists have uncovered how bacteria program their genetics to organize themselves into specific patterns within colonies, interfering with light and creating iridescence. By sequencing a wide range of bacterial DNA and developing an accurate predictive model, their findings hold great promise for sustainable, pigment-free color production.
The world is not black and white. Sometimes it is even iridescent: some organisms have shimmering nuances that change depending on the angle at which the light hits them. Think of a soap bubble, the wings of a butterfly, or the feathers of a peacock — as you move around them, their hues shift. These are examples of structural colors. Unlike pigments that absorb specific wavelengths, structural colors depend on the internal, periodic arrangement of nano-scale building blocks and how they interfere with light. This arrangement reflects certain wavelengths and blocks others, creating vivid, iridescent colors.
Bacteria can also generate structural color: not as individuals but collectively behaving in colonies, where they configure themselves according to specific patterns. For millions or even billions of bacteria in a colony to achieve structural color, it takes a great deal of organization and communication. A group of scientists from the Max Planck Institute of Colloids and Interfaces, the biotech company Hoekmine, the Universities of Utrecht, Cambridge and Jena, and others analyzed the genomes of a wide range of bacteria to find answers to these mechanisms.
The researchers first cultivated different types of bacteria in the lab and monitored their responses under LED lights, observing those that displayed color changes based on the viewing angle. “We found that structural color occurs when bacteria organize themselves in a hexagonal shape, similar to a honeycomb. This is what we call a photonic crystal,” explains Silvia Vignolini, Director of the Sustainable and Bio-inspired Materials Department at the Max Planck Institute of Colloids and Interfaces.
The next crucial step was to sequence the DNA of the bacteria. “Genomics has revolutionized science in recent years, and we suspected that genes were also responsible for structural color,” says Bas E. Dulith. This pioneering intuition proved correct: by decoding the genetic blueprints, the team identified several proteins associated with the formation of structural color. They then developed and trained an artificial intelligence model that could accurately predict which bacteria could be expected to manipulate light
Why some bacteria produce structural color, on the other hand, is still an enigma.
“We found evidence of structural color in bacteria inhabiting the deep sea, where sunlight is absent. This suggests that iridescence might be a side effect of underlying, still unidentified functions,” remarks Aldert Zomer.
Revealing the bacteria’s true colors is not just an intriguing fundamental scientific achievement, but one that holds great potential for sustainable and cost-effective manufacturing applications. The team sees their findings as taking color out of the lab and into industry. “Bacteria take up little space, are easy to feed, and multiply quickly. Imagine if we could grow them to produce colors and ditch dyes and pigments that require a lot of energy and water and are sometimes toxic,” envisions Colin Ingham.
While there's much to uncover, the prospects shimmer with promise.
