Characterization and control of biofilm and biofluid microstructure and rheology

Bacterial cells can sometimes form and thrive within biofilms, a community of cells embedded in a self-produced extracellular polysaccharide (EPS) matrix. The EPS gives biofilms three-dimensional structures, protecting cells in biofilms by making them more resistant to chemical and physical attack. It is thought that the proper characterisation of biofilms is important to design treatments for their removal. The main problem is that biofilms are very complex and often heterogeneous, making them difficult to characterise and model. In addition, the restructuring of biofilms can be a result of changes in their growth environments or even removal treatments, complicating characterisation. This thesis aims to understand how environments or treatments can change the structural features of a biofilm and also to expand the knowledge of structural heterogeneity they possess. A literature review on structural heterogeneity in different systems of biofluids summarises current knowledge in the field. The first part of the project focuses on development of a model biofilm with controlled heterogeneity, using natural polysaccharide derived from S. elodea biofilm. Here, it was found that although heterogeneity can be controlled, it can be highly variable in the relevant length scale. In the second part of the project, an E.coli biofilm was exposed to plasma treatment, a common disinfection approach. Plasma rearranges biofilm structure by local dehydration, making biofilm more resistant to subsequent treatments. Lastly, the project evaluates the effect of environmental change on the microstructure of A. xylinum biofilm by increasing viscosity of its growth medium. This biofilm produces a thick cellulose pellicle, but instead of being harmful, its properties are actually useful for many applications for example, as a scaffold in tissue engineering. Addition of alginate changes the pellicle microstructure, making it denser in an analogous effect to that of the plasma treatment studied earlier, but does not affect its actual growth process. The thesis summarises the insights gained into characterisation, modification, and engineering of biofilm properties and points to opportunities for future research and development in this area.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2018

Author dc:creator

• Kwandou, Goldina

• Rheology
• Biofilm
• Biofluid microstructure

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/21075

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/61507