exoenzyme Archives

Conceptual model for the evolution of exoenzymes and the recycling of organic matter across the Great Oxidation Event (GOE). (A) In the Archean Ocean, prior to the GOE, the recycling of organic matter depended entirely on the activity of fermenters. This resulted in low recycling efficiency, elevated carbon burial, and limited regeneration of essential nutrients back into seawater. This scarcity of particulate organic matter (POM) also reduced the availability of niches for microbial colonization, thus limiting the selective pressure for the evolution of exoenzyme systems. (b) Following the GOE, rising oxygen levels increased the availability of high-energy electron acceptors (e.g. O2, nitrate and ferric iron), supporting the expansion of metabolic groups with high exoenzyme capacity, such as aerobic heterotrophs, dissimilatory nitrate reducers and dissimilatory ferric iron reducers. Concurrently, increases in POM abundance and microbial cell densities would have amplified the selective pressure to produce exoenzymes. Collectively, these changes in the Paleoproterozoic promoted more efficient recycling of organic matter and regeneration of nutrients back into the water column, ultimately fueling greater primary productivity and oxygen release. This feedback between exoenzyme evolution, nutrient cycling, and oxygen production would have amplified Earth’s progressive oxygenation. -- biorxiv.org

Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Gaia - Planetary Perspectives, Origin & Evolution of Life, Status Report, Water/Hycean Worlds & Oceanography

Microbial Exoenzymes Catalyzed The Transition To An Oxygenated Earth

by Keith CowingOctober 11, 2025October 11, 2025

Microbial exoenzymes—extracellular enzymes secreted to degrade complex organic polymers— are essential for recycling carbon and nutrients, thus sustaining primary productivity in today’s oceans.

exoenzyme

Microbial Exoenzymes Catalyzed The Transition To An Oxygenated Earth

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Coupled AtmospHere Interior modeL Intercomparison (CHILI). I. Evolutionary Modelling — Primordial Magma Oceans of Earth and Venus