Microbial oxidation of atmospheric trace gases: from discovery to application The atmosphere provides most of the oxygen, carbon, and nitrogen essential for life, yet has long been considered too energy-poor to sustain microbial activity. Research by our team has demonstrated that diverse microbes can survive by harvesting trace amounts of hydrogen and carbon monoxide from air using high-affinity enzymes. Focusing on Mycobacterium smegmatis as a model organism, we have elucidated the physiological role, genetic regulation, and structural basis of this metabolic strategy. Our findings show that many microbes and ecosystems are variably partially or primarily powered by atmospheric energy sources. Building on this work, we are developing applications to support a circular bioeconomy, including whole-cell biocatalysis and the in vitro generation of electricity and ATP from air. These discoveries redefine the minimal requirements for life with broad scientific and technological implications.