Extreme smells—microbial production of volatile organic compounds at the limits of life

Microbial volatile organic compounds (MVOCs) are diverse molecules produced by microorganisms, ranging from mere waste byproducts to important signalling molecules. While the interest in MVOCs has been increasing steadily, there is a significant gap in our knowledge of MVOCs in extreme environments with e.g. extreme temperatures or acidity. Microorganisms in these conditions are subjected to additional stress compared to their counterparts in moderate environments and in many cases have evolved unique adaptations, including the production of specialized MVOCs. This review highlights the diversity of MVOCs identified in extreme environments or produced by isolated extremophiles. Furthermore, we explore potential applications already investigated and discuss broader implications for biotechnology, environmental biology, and astrobiology.