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Determining Mechanical Properties of Escherichia Coli by Nanoindentation

Published online by Cambridge University Press:  10 February 2012

C. A. Wright ,
C.J. Sullivan ,
B. Crawford ,
L.D. Britt ,
M.A. Mamun  and
A.A. Elmustafa
C. A. Wright
Affiliation:
Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA Applied Research Center, Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
C.J. Sullivan
Affiliation:
Department of Surgery, Eastern Virginia Medical School, Norfolk, VA 23501
B. Crawford
Affiliation:
Nanomechanics, Inc., Oak Ridge, TN 37830
L.D. Britt
Affiliation:
Department of Surgery, Eastern Virginia Medical School, Norfolk, VA 23501
M.A. Mamun
Affiliation:
Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA Applied Research Center, Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
A.A. Elmustafa
Affiliation:
Department of Mechanical and Aerospace Engineering, Old Dominion University, Norfolk, Virginia 23529, USA Applied Research Center, Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA
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Abstract

Escherichia coli, like other gram-negative bacteria, is protected from the surrounding harsh environment by a cell wall consisting of the peptidoglycan and outer membrane. Whereas the cytoplasmic membrane is the selective barrier, the cell wall provides mechanical strength for the cell. As bacteria navigate various environments, osmotic pressure can change dramatically due to changes in local solute concentration. The peptidoglycan together with the cellular proteins mitigates the osmotic stress that would otherwise cause lysis. The mechanical properties of E. coli cells and its individual layers have been largely indeterminable until the recent development of probe-based measurement tools. Since their invention, scientists have reported significant data measuring elasticity, modulus, and stiffness using atomic force microscopy (AFM). Fundamentally, in order to determine these mechanical properties through probe-based techniques, the contact area and load should be well defined. The load can be precisely calculated through the AFM cantilever spring constant. However, the silicon tip contact area can only be estimated, potentially leading to compounding uncertainties. Therefore, we developed a methodology to determine nanomechanical properties of E. coli using a nanoindenter.

Keywords

nano-indentationbiologicalbiomaterial
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1424: Symposium SS – Properties and Processes at the Nanoscale Nanomechanics of Material Behavior , 2012 , mrsf11-1424-ss04-02-oo03-02
Copyright
Copyright © Materials Research Society 2012

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