Kinetic Properties of Microbial Exoenzymes Vary With Soil Depth but Have Similar Temperature Sensitivities Through the Soil Profile

• DOI: 10.3389/fmicb.2021.735282
• Publication Date: 2021-12-01T18:13:18Z
• Authors: Ricardo J. Eloy A...; Ileana A. Callejas; Gianna L. Marschmann; Maria Mooshammer; Hans W. Singh; Bizuayehu Whitney; Margaret S. Torn; Eoin L. Brodie
• Keywords: Q10; Phosphomonoesterase; Soil carbon; Biogeochemical Cycle

Current knowledge of the mechanisms driving soil organic matter (SOM) turnover and responses to warming is mainly limited surface soils, although over 50% global carbon contained in subsoils. Deep soils have different physicochemical properties, nutrient inputs, microbiomes, which may harbor distinct functional traits lead SOM dynamics temperature responses. We hypothesized that kinetic thermal properties exoenzymes, mediate depolymerization, vary with depth, reflecting microbial adaptation substrate regimes. determined Michaelis-Menten (MM) kinetics three ubiquitous enzymes involved (C), nitrogen (N) phosphorus (P) acquisition at six depths down 90 cm a temperate forest, their sensitivity based on Arrhenius/Q10 Macromolecular Rate Theory (MMRT) models temperatures between 4-50°C. Maximal enzyme velocity (Vmax) decreased strongly depth for all enzymes, both dry mass biomass C basis, whereas affinities increased, indicating lower availability. Surprisingly, biomass-specific catalytic efficiencies also except P-acquiring enzyme, demands relative abundance. These results suggested deep microbiomes encode intrinsically and/or produce less per cell, life strategies. The varied suggesting an increase P demand or phosphatases be acquisition. Vmax efficiency increased consistently leading overall higher SOM-decomposition potential, but was similar MMRT models. In few cases, however, affected differently discrete depths, it alter depolymerization compounds. show exoenzyme reflect intrinsic adapted remarkably uniform. improve our understanding critical underlying changing through profile.