Response of Escherichia coli to hydrogen nanobubbles: an in vitro evaluation using synchrotron infrared spectroscopy.

Hydrogen (H2)-rich water, an apparent source of molecular H2, is an emerging functional drink with many purported benefits for human health (Yang et al., 2020; Ostojic, 2021). The preventive and therapeutic effects of H2 on various pathological processes have been intensively investigated in numerous clinical trials; it is commonly believed that the beneficial effects are mainly attributed to its selective antioxidant and anti-inflammatory properties (Lee et al., 2015; Ohta, 2015; LeBaron et al., 2019; Qiu et al., 2020). In recent years, a handful of rodent studies revealed that exogenous H2 can affect the gut microbiota (Sha et al., 2018; Valdes et al., 2018). For example, H2 was reported to induce a higher abundance of butyrate-producing bacteria in a rat model of Parkinson's disease (Bordoni et al., 2019). Recent first-in-human trials have explored the effects of the long-term consumption of H2-rich water on antioxidant activity and the gut flora (Sha et al., 2018; Suzuki et al., 2018). Although these promising results suggest that the intestinal microbiota may be another plausible target for molecular H2, more studies are highly warranted to explain the mechanism(s) of H2 action on bacterial growth and functions.