Monitoring the growth and drug susceptibility of individual bacteria using asynchronous magnetic bead rotation sensors b, c, ,
a The University of Michigan, Department of Chemistry, 930 N. University, Ann Arbor, MI 48109-1055, USA
b The University of Michigan, Applied Physics Program, 2477 Randall Laboratory, Ann Arbor, MI 48109-1120, USA
c The University of Michigan, Department of Biomedical Engineering, 2200 Bonisteel, Ann Arbor, MI 48109-2099, USA
d The University of Michigan, Department of Chemical Engineering, 2300 Hayward St., 3074 Dow, Ann Arbor, MI 48109-2136, USA
e The University of Michigan Health System, Clinical Microbiology and Virology Laboratories, 2F461 University Hospital, Box 5054, USA
f The University of Michigan Medical School, Department of Pathology, 1301 Catherine, Ann Arbor, MI 48109-0054, USA
Received 23 July 2010; revised 5 October 2010; accepted 6 October 2010. Available online 14 October 2010.
Abstract
Continuous growth of individual bacteria has been previously studied by direct observation using optical imaging. However, optical microscopy studies are inherently diffraction limited and limited in the number of individual cells that can be continuously monitored. Here we report on the use of the asynchronous magnetic bead rotation (AMBR) sensor, which is not diffraction limited. The AMBR sensor allows for the measurement of nanoscale growth dynamics of individual bacterial cells, over multiple generations. This torque-based magnetic bead sensor monitors variations in drag caused by the attachment and growth of a single bacterial cell. In this manner, we observed the growth and division of individual Escherichia coli, with 80-nm sensitivity to the cell length. Over the life cycle of a cell, we observed up to a 300% increase in the rotational period of the biosensor due to increased cell volume. In addition, we observed single bacterial cell growth response to antibiotics. This work demonstrates the non-microscopy limited AMBR biosensor for monitoring individual cell growth dynamics, including cell elongation, generation time, lag time, and division, as well as their sensitivity to antibiotics.
Keywords: Magnetic bead; Biosensor; Asynchronous magnetic bead rotation; Rotating magnetic field
Article Outline
1. Introduction
2. Materials and methods
2.1. Theoretical derivation
2.2. Cell culture and attachment methods
2.3. Experimental setup and measurement conditions
2.4. Experimental errors
3. Results and discussion
4. Conclusions
Acknowledgements
Appendix A. Supplementary data
References
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