Single-Cell Detection of Erwinia Amylovora Using Bio-Functionalized SIS Sensor

Abstract

Herein, we developed a bio-functionalized Solution-immersed Silicon (SIS) sensor at the single-cell level to identify Erwinia amylovora (E. amylovora), a highly infectious bacterial pathogen responsible for fire blight, which is notorious for its rapid spread and destructive impact on apple and pear orchards. This method allows for ultra-sensitive measurements without pre-amplification or labeling compared to conventional methods. To detect a single cell of E. amylovora, we used Lipopolysaccharide Transporter E (LptE), which is involved in the assembly of lipopolysaccharide (LPS) at the surface of the outer membrane of E. amylovora, as a capture agent. We confirmed that LptE interacts with E. amylovora via LPS through in-house ELISA analysis, then used to construct the sensor chip by immobilizing the capture molecule on the sensor surface modified with 3′-Aminopropyl triethoxysilane (APTES) and glutaraldehyde (GA). The LptE-based SIS sensor exhibited rapid (< 10 min) detection of the target bacterial cell in real time. The sensor showed the value change (dΨ) of approximately 0.008° for growing overlayer thickness induced from a single-cell E. amylovora, while no change in the control bacterial cell (Bacillus subtilis) was observed. The dose-response curve shows linearity (R2 > 0.99) with wild dynamic ranges from 1 to 107 cells/mL for the target bacterial pathogen. Taken together, our system has the potential to be applied in fields where early symptoms are not observed and where single-cell or ultra-sensitive detection is required, such as plant bacterial pathogens detection, foodborne pathogen monitoring and analysis, and pathogenic microbial diagnosis.

Keywords: Single-cell detection, LptE, Solution-immersed silicon, biosensor, Erwinia amylovora