Life co-evolved along with Earth’s changing environmental conditions and the reconstruction of the evolutionary history of key biochemical functions and microbial adaptation is critical to understand this process. The lineages that led to modern microorganisms that inhabit “relic” environments that resemble the early Earth (e.g. deep-sea vents) co-evolved with our planet for billions of years. Hence, the genomes of modern vent microorganisms carry both ancestral and recently acquired genes and provide excellent models to reconstruct how microbial metabolism evolved and adapted to Earth’s changing environmental conditions. In the DSML we carry out comparative genomic analyses of deeply-branching microorganisms to reconstruct the evolutionary history of microbial adaptation. Read about our recent papers on eLife, Scientia and The Biochemist on this topic.