The majority of microbial cells in global soils exist in a spectrum of dormant states. However, the metabolic processes that enable them to survive environmental challenges, notably organic carbon and oxygen limitation, remain to be elucidated. We have shown that atmospheric trace gases such as molecular hydrogen (H2) serve as alternative fuel sources for aerobic soil bacteria. Genetic and biochemical studies focused showed that the aerobic respiration of such gases sustains the maintenance energy of carbon-exhausted cells and greatly enhance their long-term survival. In addition, we have shown that these obligately aerobic bacteria survive hypoxia through an anaerobe-type strategy: fermentative degradation of organic carbon reserves leading to H2 production. Bacteria tightly and coordinately regulate the processes of atmospheric H2 oxidation and fermentative H2 production in response to environmental signals in order to maintain energy and redox homeostasis. Our pure culture studies show that these processes sustain representatives of at least four of the dominant soil phyla, i.e. Actinobacteria, Acidobacteria, Verrucomicrobia, and Chloroflexi. In addition, genomic and metagenomic surveys revealed that the hydrogenase genes mediating these activities are ubiquitous. These findings in turn have implications for understanding microbial ecology and nutrient cycling in global soil ecosystems.