In Living Color: Bacterial Pigments as an Untapped Resource in the Classroom and Beyond

Abstract

Recent advances in the study of natural products made by bacteria have laid the foundation for engineering these molecules and for developing cost-effective ways to manufacture them. In our lab, we study a number of natural products that are synthesized by harmless soil bacteria of the Streptomyces genus. Whereas our primary interest in these molecules is due to their antibiotic properties, many of these natural products have distinct colors [1]. (The reasons for why Streptomyces make antibiotics or pigments remain mysterious.) This article is intended to make the case to the scientific and educational communities that Streptomyces-derived natural products are an untapped source of useful biopigments. By sharing some of our own experiences in harnessing these pigments to create paint and paintings, we also hope to inspire others to explore the potential of Streptomyces-derived pigments in art, industry, and perhaps most importantly, the classroom. The pedagogical value of bacterial pigments is highlighted by the wide range of concepts and methods in chemistry, biology, and art that can be introduced to students in this context (see Box 1). Teachers can incorporate bacterial pigments into their lessons while introducing fundamental scientific principles ranging from the physics of color to the chemistry behind paints that fade in sunlight. Painting with living bacteria (Box 2) or extracting pigments from bacterial cultures (Box 3) provides a visual and kinesthetic activity to support key aspects of scientific investigations and methods learned in the classroom. Because the methods to do so are safe, inexpensive, and easily implementable in the everyday world, it is possible to use biopigments as a vehicle to introduce school children to science via art and vice versa. While many of these concepts and techniques are appropriate for the advanced high school or undergraduate classroom, even elementary school children can use bacterial paints prepared by their teacher to create art, an activity that may teach children at a young age that bacteria are a source of valuable materials rather than merely agents of disease. Box 1: Concepts at a Glance Leads into chemistry, microbiology, and biotechnology Chemical composition of paint (solubility and states of matter)¥, ‡ Structures of pigment molecules (electromagnetic radiation, electron configuration, valence bonds, molecular orbital theory)‡ Culturing Streptomyces and extracting their pigments (sterile culture techniques, natural product extraction techniques, solubility)‡ Painting Streptomyces on agar plates (bacterial growth control)¥,‡ Engineering bacteria to make new pigments (metabolic engineering of microbial systems)‡ Scaling up the production of bacterial pigments (large scale bioprocessing techniques, recombinant DNA technology)‡ UV absorber and radical scavengers as additives to paints (chemical structure and reactivity, radical reactions)‡ Leads into fine arts The perception of color (electromagnetic radiation, the eye as a spectrometer)¥, ‡ Paint constituents (pigments, binders, solvents, surfactants, additives)‡ Sources of pigments‡ Making paints from pigments (grinding pigments, suspending in binder)¥, ‡ History of pigments (art history)*, ¥, ‡ Fun stuff Drawing on paper with bacteria-derived paint*, ¥, ‡ Creating living art by painting with bacteria on agar medium*, ¥, ‡ ‡ = for undergraduate or advanced placement high school courses; ¥ = for high school courses; * = for elementary school courses