Detecting and differentiating Escherichia coli strain TOP10 using optical textures of liquid crystals

Abstract

We report a method for detecting Escherichia coli using a nematic liquid crystal (LC), 4-cyano-4′-pentylbiphenyl (5CB). Among three E. coli strains tested, TOP10 strain grown on agar plates induces a homeotropic orientation of LCs whereas DH5α and JM109 strains do not. This results in a clear distinction in the optical appearance of LCs as either uniformly dark or bright under polarised light. The LC-based method provides a simple, rapid and low-cost method of identifying E. coli strains.

Keywords:

• Escherichia coli
• optical sensor
• 5CB
• differentiate

Acknowledgements

This work was supported by research funding from the National University of Singapore and the Agency for Science, Technology and Research (A*STAR), Singapore. The E. coli samples were kindly provided by Dr Lianhui Zhang from the Institute of Molecular and Cell Biology (IMCB), Singapore, and Dr Jianzhong He from the Division of Environmental Science and Engineering, National University of Singapore.