R&D Profile: Phage Reporter Biosensing of Pathogenic Agents
Bacteriophage, or bacterial viruses, are considered natureâ€™s most abundant nano-entity.Profile Courtesy of Steve Ripp, Research Assistant Professor, The University of Tennessee, US
Bacteriophage are estimated to exist at population levels approaching 1031. Bacteriophage survive and persist by infecting and propagating themselves within bacterial cells, and they can do so with remarkable specificity for their bacterial hosts. For example, certain bacteriophage will infect E. coli cells but no other bacterial genera or species. This host range specificity has been taken advantage of for decades in medical diagnostics where a pathogenic bacterium can be identified based on which bacteriophage actively infect it, in what is called phage typing.
More recently, phage typing has evolved to include genetically engineered bacteriophage reporters that carry with them signaling elements that are transferred to their bacterial hosts upon infection. These signals are chosen based on ease of measurement, and typically include light emitting proteins such as green fluorescent protein (GFP) and bioluminescent Lux and Luc, although quantum dots are beginning to make headway as well.
In our laboratory, we have infused bacteriophage with the bioluminescent lux genes, and can detect bacterial pathogens simply by assaying for light production using any number of photodiode or photomultiplier instruments. The assay has been optimized for the detection of E. coli O157:H7 in food and water sources, but substituting phage reporters specific for other bacterial pathogens permits near limitless detection profiling. The assay has been tested in contaminated water, apple juice, eggs, poultry, and spinach leaf rinsates, and detection limits down to 1 cell can be established in less than 24 hour assays.
To accommodate lab-on-a-chip sensing needs, we have additionally developed an accompanying miniaturized integrated circuit microluminometer that detects the bacteriophage induced bioluminescent light signal. This so-called bioluminescent bioreporter integrated circuit, or BBIC, represents a standalone sensing and monitoring platform that can be plug-and-play incorporated into any user desired assay format for remote, field portable surveillance.