Molecular Hydrogen Metabolism: a Widespread Trait of Pathogenic Bacteria and Protists.

Abstract

This review comprehensively examines the distribution, biochemistry, and physiology of molecular hydrogen (H2) metabolism across pathogenic microorganisms. Genes encoding hydrogenases—enzymes catalyzing H2 oxidation and/or production—are present in more than 200 pathogens and pathobionts, with experimental evidence for H2 consumption or production confirmed in at least 46 species. Several major gastrointestinal pathogens, including Salmonella enterica serovar Typhimurium, exploit the abundant H2 generated by colonic microbiota as an energy source supporting both aerobic and anaerobic respiration, a process linked to bacterial growth and virulence. H2 oxidation is typically a facultative trait regulated by central metabolic sensors responding to energy status and oxidant availability. Conversely, facultative and obligate anaerobic pathogens release H2 as a fermentation end product. The review also identifies gaps in understanding H2 transactions in obligately anaerobic bacteria and discusses H2 metabolism as a potential target for antimicrobial drug development.

Mechanism

Hydrogenases enable pathogens to oxidize H2 as an electron donor for aerobic or anaerobic respiration, supporting growth and virulence. In fermentative pathways, H2 is released as a diffusible end product, with expression regulated by energy and oxidant availability sensors.