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Shaping bacterial cellulose with wave physics

Cellulose is the Earth’s most common organic material. We are usually most familiar with plant cellulose but bacteria are also huge cellulose producers.

Many bacteria produce cellulose as part of the protective biofilms they secrete. Bacterial cellulose has the same molecular formula as plant cellulose, but has significantly different properties and characteristics. In general, microbial cellulose is chemically purer, forms much finer fibrils, has a higher water holding capacity and greater tensile strength resulting from its ultrafine network and a larger amount of crosslinking. Bacterial cellulose can be produced on a variety of substrates, fed with biowaste and can be grown to virtually any shape.

Bacterial cellulose has a wide variety of current and potential applications. It is being used in the food industry, medicine, commerce, and other emerging technical areas. Some of the applications include tissue scaffolds, ultra-strength papers and textiles, and potential electronic papers and fuel cells.

A research team at The Australian National University (ANU) lead by Dr Hua Xia and Dr Sung-Ha Hong have developed a way to use waves in water to manipulate the growth of bacterial biofilms.

Dr Hua Xia had previously shown that surface waves, created with simple wave generators, can control water flow patterns, enabling them to move floating objects at will. They then applied this technique to bacteria growing in controlled conditions in the lab. They discovered that the growth of biofilms could be promoted or inhibited by different wave patterns.

Turbulent motion was found to discourage the attachment of bacteria to a surface and prevents biofilm formation. In contrast, stationary wave patterns encourage a patterned growth of biofilms. This is due to the wave-driven flows generating localised transport routes that deliver oxygen. The wave action is the strongest at the liquid-air interface, where bacterial cellulose can form. This wave-based approach could help to engineer bacterial cellulose into new structures for many exciting new applications

The research group at the ANU are now focused on creating various cellulose forms and controlling their properties, such as water holding capacity and mechanical strength.

Confocal laser scanning microscopy at Microscopy Australia’s ANU facility, the Centre for Advanced Microscopy, was used to study patterns of the biofilm during its formation.

This project is supported by the ARC Discovery Project: DP190100406.
Surface waves control bacterial attachment and formation of biofilms in thin layers Sung-Ha Hong, Jean-Baptiste Gorce, Horst Punzmann, Nicolas Francois, Michael Shats, Hua Xia Science Advances 27 May 2020 : eaaz9386

Fluorescent image of the biofilm formed under the wave excitation. Lighter colours correspond to thicker biofilm. Reconstructed 3D surface of the biofilm using the confocal laser scanning microscopy at two regions of interest indicated by the red boxes.