(62ae) Assembly of Bacteria at Oil-Water Interfaces

The way bacteria assemble themselves at oil-water interfaces and how they behave when encapsulated in double emulsions is of interest both for determining what the stabilization properties of the bacteria are and for studying gene expression in varying conditions. Previous research has only studied hydrophobic bacteria at the interfaces of single emulsions. The unique aspect of this experimentation is that, along with simple techniques, microfluidic devices were used to produce both single and double emulsion droplets of controlled sizes. Bacillus subtilis, Pseudomonas aeruginosa, and Escherichia coli bacteria were used for the experimentation, each having certain distinct characteristics and providing variation. Single emulsions were made with silicone oil, alone with ten other oils to further determine what the cause of stabilization. Double emulsions with concentrated bacteria solutions were prepared in an attempt to fill the droplets and grow a biofilm. The testing confirmed that E. coli and silicone oil are the most successful combination for producing a stable emulsion. Testing different oils also showed that the stability of the emulsions increased as the number of carbons in the chemical structure increased. Through experimentation some interesting properties of ferrofluids, when emulsified with bacteria were discovered. P. aeruginosa, which sometimes oriented themselves vertically, were the only bacteria that showed any organized or specific arrangement at the oil-water interface.