Investigating The Effect Of Hydrogen Ultrafine Bubbles On Bacterial Growth

Abstract

Several previous studies have considered ultrafine bubbles (UFBs) as a potential research target because their properties can be applied in many different research areas. In particular, the interaction between UFBs and microorganisms has always been one of the affairs receiving much attention since controlling a living system is difficult. Furthermore, the properties of UFBs, as moving air-water interfaces, are greatly determined by their gas cores. The type of chosen gas for inducing UFBs plays a critical role in regulating microorganism growth. This study aimed to investigate the effects of hydrogen ultrafine bubbles on bacterial growth. Study subjects included two well-studied organisms - Escherichia coli and Staphylococcus aureus. Their growing behavior was examined based on the growth rate, phenotype and biomass. Three types of Luria-Bertani cultures were tested, including standard culture containing distilled water (DW), air ultrafine bubble (AUFB) culture and hydrogen ultrafine bubble (HUFB) culture. The UFBs were generated via ultrasonication and stabilized by 0.05 mM SDS, which was proven to have negligible effects on bacterial growth. By comparing among three types of cultivation conditions, the bacterial growth rates were obtained to be the highest in exposure to HUFBs. The results also signified that UFBs had an enhancement influence on cell proliferation (there was no overlap among the error bars on the growth curves). On the other hand, while proposing an increase in cell density, bacteria cultured in HUFB culture media decreased their sizes uniformly and significantly (p-value less than 0.05, obtained from statistical t test). The optical density of bacterial population was measured at 600nm whilst the optical microscopic images were used to observe their morphology. Ultimately, this study confirmed that bacterial growth was promoted by UFBs, the better effects recorded from HUFB culture media. However, the sizes of bacteria also became smaller along with their population enlargement.