In an effort to develop simple techniques for measuring caffeine in beverages, students in Dr. Jeff Barrick’s lab have engineered E. coli strains to feed off it.
Caffeine is often toxic to bacterial species. However, one P. putida variant contains a multi-enzyme pathway that can degrade caffeine into xanthine and formaldehyde. Xanthine in turn is an intermediate in guanine synthesis – which is necessary for growth. By introducing this P. putida gene set into an E. coli strain incapable of making guanine, new E. coli strains were engineered to be dependent on caffeine for growth.
Their results were published in ACS and should be simple enough to use in high schools to measure caffeine concentrations.