By leveraging the unique qualities of microorganisms, engineered living materials (ELMs) offer functional and economic advantages in everyday applications along with notable ecological benefits. This study contributes to the growing field of biodesign by examining the potential of Flavobacteria for thermochromic ELMs. Many Flavobacteria, commonly found in marine environments, produce iridescent structural colorations as their colonies expand on semi-solid surfaces through gliding motility. In this study, we analyzed the effects of temperature variations on flavobacterium Cellulophaga lytica PLY-A2, characterizing distinct changes in colony growth and iridescent colorations at a macroscopic and microscopic scale. Using scanning electron microscopy, we investigated the relationship between iridescent color and the underlying cell-based optical structures. By providing insights into the temperature-responsive behavior of Flavobacteria, our findings highlight their potential for future thermochromic ELMs—with applications ranging from sustainable food packaging to smart textiles—while encouraging further characterization studies within biodesign research.

Flavobacteria, which can be found in marine environments, are able to grow in highly organized colonies producing vivid iridescent colorations. While much is known about the biology of these organisms, their design potential as responsive media in user interfaces has not been explored. Our paper aims at bridging this gap by providing insights into the type, degree, and duration of change in Flavobacteria's expression, i.e., their living aesthetics. We present a tool to capture and characterize these changes concerning form, texture and iridescent color. To support the long-term study of their living aesthetics, we designed Flavorium. This bio-digital artifact provides the necessary habitat conditions for Flavobacteria to thrive for a month. Granting insights into the responsive behavior of this organism, this work presents a design space, vocabulary, and application concepts to inspire HCI and design scholars to investigate the complex temporal qualities of living media for future user interfaces.

Flavobacterium IR1 is a gliding bacterium with a high degree of colonial organization as a 2D photonic crystal, resulting in vivid structural coloration when illuminated. Enterobacter cloacae B12, an unrelated bacterium, was isolated from the brown macroalga Fucus vesiculosus from the same location as IR1. IR1 was found to be a predator of B12. A process of surrounding, infiltration, undercutting and killing of B12 supported improved growth of IR1. A combination of motility and capillarity facilitated the engulfment of B12 colonies by IR1. Predation was independent of illumination. Mutants of IR1 that formed photonic crystals less effectively than the wild type were reduced in predation. Conversely, formation of a photonic crystal was not advantageous in resisting predation by Rhodococcus spp. PIR4. These observations suggest that the organization required to create structural colour has a biological function (facilitating predation) but one that is not directly related to the photonic properties of the colony. This work is the first experimental evidence supporting a role for this widespread type of cell organization in the Flavobacteriia.