Growing colours, literally

Print edition : March 16, 2018

A bacterial colony.

The distinctive colour patterns seen in natural things such as butterfly wings and peacock feathers have often left both scientists and commoners awestruck. Now, a team of researchers from the University of Cambridge working closely with a Dutch company has cracked the genetic code behind some of the brightest and most vibrant colours in nature.

In what could possibly be one of the first studies into the genetics of structural colour, the scientists showed how genes could be tweaked to change the hues and appearance of certain bright-coloured bacteria. The work, which appeared in the journal Proceedings of the National Academy of Sciences can open up new avenues of harnessing these bacteria for the large-scale manufacturing of biodegradable, non-toxic paints, for instance.

Flavobacterium is a type of bacteria that packs together in colonies that produce bright metallic colours that come not from pigments but from their internal structure, which reflects light at certain wavelengths. Scientists continue to wonder how these intricate structures are genetically engineered by nature. “It is crucial to map the genes responsible for the structural colouration for further understanding of how nanostructures are engineered in nature,” said first author Villads Egede Johansen, from Cambridge’s Department of Chemistry. “This is the first systematic study of the genes underpinning structural colours—not only in bacteria, but in any living system.”

The researchers compared the genetic information to the optical properties and anatomy of wild-type and mutated bacterial colonies to understand how genes regulate the colour of the colony. By genetically mutating the bacteria, the researchers changed their dimensions or their ability to move, which altered the geometry of the colonies. By changing the geometry, they changed the colour: they changed the original metallic green colour of the colony in the entire visible range from blue to red. They were also able to create duller colouration or make the colour disappear entirely. In the process, the scientists also mapped genes with previously unknown functions and correlated them to self-organisation capacity and colouration of these bacterial colonies.

The scientists hope that this bacterial system can be exploited to fabricate tuneable photonic nanostructures that can be reproduced in abundance. This can potentially lead to the manufacture of biodegradable paints for automobiles or walls, they said.

T.V. Jayan