Washington University Researchers Develop Tool to Weed Out Lazy Bacteria

Engineers at Washington University in St. Louis discovered a way to improve production of biofuels and other chemicals by capitalizing on the work ethic of cells.

The team, led by Dr. Fuzhong Zhang, assistant professor of energy, environmental & chemical engineering in the School of Engineering & Applied Science, discovered that genetically identical microbial cells have different work ethics. Only a small fraction of cells worked hard to produce the desired chemicals, while others were content to just eat nutrients intended for working cells.

Zhang's team developed a quality-control tool, PopQC, to keep high-performing cells working while eliminating the lazy cells. The team placed a sensor inside the cells that sense the work each cell was doing. If a cell was working hard, the sensor would trigger a controller to make a protein that allowed the cells to survive and grow. If the cell was not working hard enough, the sensor remained silent, and the lazy cells died from lack of nutrition or were knocked out by antibiotics.

The team applied PopQC to two engineered strains of E. coli: one designed to produce free fatty acid, a precursor for biofuels or other high-volume chemicals; and one designed to produce tyrosine, an amino acid that can be a precursor to pharmaceuticals. PopQC allowed the hard-working cells to dominate in both cultures and led to three-fold enhanced ensemble production of both free fatty acid and tyrosine.