Rapid label-free detection of E. coli using a novel SPR biosensor containing a fragment of tail protein from phage lambda

Abstract

In efforts to speed up the assessment of microorganisms, researchers have sought to use bacteriophages as a biosensing tool, due to their host-specificity, wide abundance, and safety. However, the lytic cycle of the phage has limited its efficacy as a biosensor. Here, we cloned a fragment of tail protein J from phage lambda and characterized its binding with the host, E. coli K-12, and other microorganism. The N-terminus of J was fused with a His-tag (6HN-J), overexpressed, purified, and characterized using anti-His monoclonal antibodies. The purified protein demonstrated a size of ∼38 kDa upon SDS-PAGE and bound with the anti-His monoclonal antibodies. ELISA, dot blot, and TEM data revealed that it specifically bound to E. coli K-12, but not to Pseudomonas aeruginosa. The observed protein binding occurred over a concentration range of 0.01–5 μg/ml and was found to inhibit the in vivo adsorption of phage to host cells. This specific binding was exploited by surface plasmon resonance (SPR) to generate a novel 6HN-J-functionalized SPR biosensor. This biosensor showed rapid label-free detection of E. coli K-12 in the range of 2 × 10⁴ −2 × 10⁹ CFU/ml, and exhibited a lower detection limit of 2 × 10⁴ CFU/ml.

Keywords:

• Bacteriophage lambda; E. coli K-12
• SPR
• tail protein

Acknowledgments

The authors thank M.S. Kim, G.W. Kim, D.H. Lee, and S.H. Hyeon for helping with the laboratory work.

Additional information

Funding

This work was supported by a Frontier grant (2016) and partly by a grant from the Innovation Center for Engineering Education of Dongseo University, Republic of Korea. Professor Shin is the recipient of a Basic Science Research Program (2016R1D1A1B01015961) through the National Research Foundation of Korea (NRF) funded by the Ministry of Education.