Structural colour in marine organisms: From nature to applications

Abstract

Structural colouration, arising from the interaction of light with transparent materials featuring lengths comparable to visible wavelengths, is a fascinating phenomenon responsible for the appearance of many living organisms. Over the past few decades, such mechanism has been proposed to develop alternatives to traditional dye-based pigments as it allows for the production of bright and vivid colourations using sustainable materials. Whilst structural colour has been extensively studied in terrestrial animals and plants, marine organisms have begun receiving attention only recently. This thesis explores the prevalence and functional significance of structural colouration in seaweeds. By examining a variety of nano-architectures in diverse macroalgae from both green and red algal groups, I aim to shed light on how widespread this phenomenon is and its potential roles in light management, such as photoprotection or enhancing photosynthesis. In the second part of this thesis, I study how some rod-shaped gliding bacteria, such as Flavobacterium IR1 or Cellulophaga lytica, which form highly ordered two-dimensional photonic crystals when grown in biofilms, can be used to develop sustainable photonic pigments. Specifically, I utilise C. lytica to fabricate photonic particles through a straightforward protocol. This proof-of-concept work holds promise for scaling up to produce biological ’glitters’ and pioneering new, sustainable optical biomaterials.