Bacteriophages Long Tail Fiber Proteins as a Biometric Element in Electrochemical Biosensors for the Detection of Salmonella in Lake Water

Abstract

Salmonella is a common foodborne pathogen and one of the key causes of diarrhea. Some direct contact with infected animals, food, and water may cause harm to human health. Therefore, achieving rapid and sensitive detection of Salmonella is vital to control its spread. In this study, based on the genetic information of Salmonella enterica phage (SEP37), we found that ORF99, ORF100, and chaperone ORF256 are tail genes associated with host recognition. Therefore, the pETdue1 plasmid was used to construct ORF99-ORF100 and ORF256 co-expression vectors to express long tail fiber proteins (LTFPs) in Escherichia coli (E. coli) and use LTFPs as specific biometric elements. Then, AuNPs, cysteamine (Cys), and LTFPs are fixed on the gold disk electrode (GDE) surface by layer-by-layer assembly to construct an electrochemical impedance spectroscopy (EIS) biosensor. In the sensor, salmonella in the sample can be captured by LTFPs on the electrode surface and cause the reduction of electron transfer sites. In this method, the working electrode only needs to be incubated with the sample for 40min to detect electrical signals, significantly reducing time compared to traditional culture methods (1~4 days). The EIS sensor developed was then applied to detect salmonella spiked in lake water, which showed a good linear relationship within the concentration range of 10 ~ 1×106 CFU/mL. The detection limit is as low as 9 CFU/mL. This method based on bacteriophage LTFPs does not need complex pretreatment steps and extends tail fiber protein's application as a bio-recognition element in the detection field.

Keywords: Salmonella, Long tail fiber proteins (LTFPs), Electrochemical impedance spectroscopy, Biosensors, Rapid detection