Effects of Ultrafine Bubbles on Gram-Negative Bacteria: Inhibition or Selection?

Ultrafine bubbles exist in all liquids and are naturally stable. As their properties are not entirely known, it is unclear how they impact the surrounding solution and comparable-sized particles within it. It is essential to further investigate the properties of ultrafine bubbles in order to expand their industrial application. In this regard, the effect of ultrafine bubbles on bacterial development is of particular interest. Our current study, using optical density measurements and fluorescence microscopic images has demonstrated that ultrafine gas bubbles impact the morphology and phenotype of Escherichia coli and Pseudomonas aeruginosa. Specifically, Fourier transform infrared spectroscopic measurements indicated a thickening of bacterial membranes in samples exposed to ultrafine bubbles. The study also confirmed that ultrafine bubbles can inhibit bacterial cell growth. This study signifies the role of surface phenomena in bacterial culture, which is crucial in the upstream processes of recombinant DNA technology applications.