Developing a Chromogenic Protein Model Adapted to High School STEM Research and Education

Abstract

Chromogenic protein (CP) is a naturally occurring polypeptide produced by the coral species Acropora millepora. To employ its chromogenic properties for use in bacteria, we synthesized a codon-optimized CP gene and placed it under control of a rhamnose-inducible promoter (rha) for expression in Escherichia coli. To expand the array of chromogenic phenotypes available in E. coli, we developed a mutagenesis strategy using inverse PCR to change the DNA sequence encoding glutamine, a component of the chromophore found at position 62 of CP, to all 19 other amino acids. Strikingly, expression of many of these variants in E. coli imparted a colorful array of phenotypes to the bacteria, including purple, which is produced by the wild-type protein. This collection of CP mutants, and associated methods for expression and mutagenesis, have been incorporated into undergraduate microbial genetics curriculum as a teaching tool to reinforce the basic principles of the central dogma, including gene regulation, mutagenesis and translation, through informational suppression. This model also holds potential for high school students as a visually engaging system for introducing students to molecular biology and sparking interest in STEM, research, and biotechnology, as well as a research tool to differentiate between bacterial strains in synthetic communities.