Microbial extracellular hydrolase activity and kinetics in the deep ocean
ID：1379
Poster Presentation
2027-01-15 16:45 （China Standard Time）
Session：Session 7 - Under Pressure: Microbial Carbon Cycling and Organic Matter Transformation in the Deep Ocean
Abstract
The deep-sea carbon cycle is a critical yet still enigmatic component of Earth’s climate system, where high hydrostatic pressure severely limits our ability to probe in situ microbial-driven processes and estimate carbon fluxes. A key bottleneck lies in characterizing specific extracellular hydrolase activities under in situ pressure regimes, as these hydrolases mediate the rate-limiting step of organic matter degradation. We developed a pressure-retaining sampling and incubation system to measure potential activity and apparent kinetics of extracellular hydrolases secreted by deep-sea microbial communities in the Western Pacific under simulated in situ pressure. Our results reveal a pressure-dependent divergence in the specific extracellular hydrolase responses: increasing hydrostatic pressure (with depth) consistently suppressed bulk alkaline phosphatase activity, while markedly stimulating β-glucosidase, β-N-acetylglucosaminidase, and leucine aminopeptidase activities. Community-level enzyme kinetic analyses revealed increased substrate affinity (reflected by decreased half-saturation constants, Km) of β-glucosidase, β-N-acetylglucosaminidase, and alkaline phosphatase under high hydrostatic pressure, whereas leucine aminopeptidase showed decreased affinity but the most pronounced pressure-induced increase in maximum reaction rate. Based on these observed extracellular hydrolase activities, an ecoenzymatic stoichiometry model predicted elevated microbial growth efficiency under high hydrostatic pressure compared to atmospheric pressure, with a concomitant relief of carbon limitation, as validated by concurrent measurements of biomass production and respiration under simulated high pressure. This study demonstrates that despite low organic matter concentrations, the deep ocean sustains microbial communities with high carbon-use efficiency, driving an enhanced proportion of carbon retention in biomass and thereby promoting carbon storage in the ocean interior.
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Important Dates
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Jan 30
2026
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Mar 31
2026
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Sep 15
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Jan 12–15
2027
XMAS 2027