In 2008, James Collins, a biologist at Boston University, and Tim Lu of MIT published details of the first phage engineered to kill. Their new phage is especially effective because it’s tailored to attack the rubbery sheets that bacteria embed themselves in, known as biofilms. Biofilm can foil antibiotics and phages alike, because they can’t penetrate the tough goo and reach the bacteria inside. Collins and Lu searched through the scientific literature for a gene that might make phages better able to destroy biofilms. Bacteria themselves carry enzymes that they use to loosen up biofilms when it’s time for them to break free and float away to colonize new habitats. So Collins and Lu synthesized a gene for one of these biofilm-dissolving enzymes and inserted it into a phage. They then tweaked the phage’s DNA so that it would produce lots of the enzyme as soon as it entered a host microbe. When they unleashed it on biofilms of E. coli, the phages penetrated the microbes on the top of the biofilms and forced them to make both new phages and new enzymes. The infected microbes burst open, releasing enzymes that sliced open deeper layers of the biofilms, which the phages could infect. The engineered phages can wipe 99.997 percent of the E. coli in a biofilm, a kill rate that’s about a hundred times better than ordinary phages.

Taken from: A Planet of Viruses (by Carl Zimmer)