The effects of size and shape changes on motility in Escherichia coli (AW405)

Thornton, Katie Louise

Biological sciences
September 2015

Thesis or dissertation


Rights
© 2015 Katie Louise Thornton. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.
Abstract

Many microorganisms from all domains of life invest large quantities of energy on locomotion. Adopting a motile lifestyle, although energetically costly, increases the likelihood of encounters with food and nutrients, and reduces the risks of predation or prolonged contact with toxic environments. Understanding the reasons behind these costly adaptations, and discovering the most economical methods for locomotion at the microscopic scale could generate further understanding of many ecological processes at this scale, including; the mechanics of locomotion, food web dynamics, evolutionary pathways and the fluid mechanics of biological systems. Consequently, this project focuses on using the key laboratory bacterial species Escherichia coli, to investigate the effect of changes in body shape (aspect ratio) and size on a variety of movement behaviours.

E. coli cells treated with the antibiotic cephalexin grow into filamentous forms. Longer cells were found to swim more slowly than normally shaped cells. Run speed was significantly negatively correlated with increases in cell length (F 1, 8858 = 130.5; P<0.001), with speed decreasing approximately -0.109 micrometres per second for each micrometre increase in cell length. Elongation of the cell was also found to impact up the cell’s ability to ‘tumble’ (re-orientate), with cells >10μm in length being observed to ‘run and reverse’, rather than ‘run and tumble’. Overall, changes in cell shape significantly altered the motile behaviours of E. coli cells.

These results suggest that body shape is essential for the successful locomotion of microorganisms, and further study is needed to uncover the evolutionary purposes behind the diverse array of shapes observed in nature.

Publisher
Department of Biological, Biomedical and Environmental Sciences, The University of Hull
Supervisor
Humphries, Stuart
Qualification level
Masters
Qualification name
MSc
Language
English
Extent
2 MB
Identifier
hull:13765
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