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Mechanical Properties of Bacterial Fibres

Published online by Cambridge University Press:  21 February 2011

John J Thwaites  and
Neil H. Mendelson
John J Thwaites
Affiliation:
Dept. of Engineering Cambridge University
Neil H. Mendelson
Affiliation:
Dept. of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona
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Abstract

Bacterial thread is the name given to a fibrillar fiber produced from cell-separation-suppressed mutants of Bacillus subtilis. which grow in long cellular filaments and produce in cultures aggregates that resemble randomly-laid textile webs. Threads are produced by steady withdrawal at the end of a sterile toothpick - for all the world like Carothers, 50 years ago! Individual filaments are drawn radially into the forming thread and adhere strongly to each other with axial alignment. Uniform threads up to 1 meter in length and 180 μm in diameter can be produced. Such threads contain about 50,000 filaments and upwards of 1010 cells Tests on thread show that peptidoglycan, which is the load-bearing polymer of the bacterial cell wall, behaves mechanically like other visco-elastic polymers. When dry its behavior is glassy, with high modulus; when wet, it is relatively weak and of low initital modulus. Relaxation data indicate a very wide spectrum of relaxation times. All the mechanical properties depend strongly on the RH of the test environment; they are also influenced by the ionic environment at the time threads are drawn. Available evidence indicates that peptidoglycan is not crystaline. Nonetheless there is some degree of orientation in the bacterial cell wall. This is shown by the effect of enzyme attack on mechanical properties and by the twisted growth pattern of bacteria.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 174: Symposium R – Materials Synthesis Utilizing Biological Processes , 1989 , 179
Copyright
Copyright © Materials Research Society 1990

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