SYNTHETIC BIOLOGY FOR FOOD AND WATER SAFETY SOLUTIONS
The Nugen Research Group, led by Professor Sam Nugen, is located in Stocking Hall in the Department of Food Science at Cornell University, Ithaca, NY.
Our research focuses on synthetic biology or genetic engineering of Enterobacteria phage based biosensors or nanobots to support the development of novel, highly specific, rapid, low-cost pathogen separation and detection technologies. These technologies can be practically used to routinely test drinking and process water, liquid foods, and surface swabs of food processing and packaging equipment.
Expanding the Phage Host Range
As pathogen recognition elements, phages target, infect, and lyse a very narrow range of Enterobacteria, including Salmonella, Listeria, and E. coli. Phages recognize only viable host cells, which makes them unique among current pathogen detection technologies commonly employed.
Our research group utilizes novel approaches to genetically engineer phage in ways that increase our understanding of host range and infectivity, and result in strains that have a high level of inclusivity for a range of Enterobacteria species considered to be pathogenic. The average phage genome is quite small and the strains we use are well documented, thus facilitating genetic manipulation. T4 bacteriophage tail fibers play a primary role in host cell recognition, and genetic modification of these structures may increase host range.
Enhancing Pathogen Separation
Further separation and concentration of the captured host bacterial cells can increase the sensitivity of phage based detection technologies. We test strategies to covalently and non-covalently conjugate various coated magnetic nanoparticles to the phage capsid, a structure that is free during phage host recognition and binding. Nano-magnetic phages can be easily concentrated by centrifugation or magnetic separation, allowing also for the concentration of bound pathogen cells.
Immobilization of phages to a support or substrate such as a filter can result in the capture of low levels of pathogen in large volume samples such as drinking water. The phage capsid gene can also be modified to express a ligand such as a biotin receptor peptide, a monomeric streptavidin, or a cellulose binding module to allow immobilization directly onto a cellulose or surface-modified filter.
Reporter Phages
Common pathogen detection systems utilize various reporter molecules such as dyes, fluorescent or luminescent probes, or enzymes for visualization of the target pathogen. We engineer phage genomes with reporter enzymes such as luciferases that are expressed by the host bacteria afterphage infection and before cell lysis. Addition of enzyme substrate after this burst of enzyme release during “reporter phage” infection results in a product that can be visualized by the naked eye or image captured.
