Biogeochemistry

, Volume 131, Issue 1–2, pp 163–172

Aging exo-enzymes can create temporally shifting, temperature-dependent resource landscapes for microbes

  • Sharon Billings
  • K. Min
  • F. BallantyneIV
  • Y. Chen
  • M. Sellers
Article

DOI: 10.1007/s10533-016-0273-x

Cite this article as:
Billings, S., Min, K., Ballantyne, F. et al. Biogeochemistry (2016) 131: 163. doi:10.1007/s10533-016-0273-x

Abstract

The rate at which catalytic capacity of microbial exo-enzymes degrades post-exudation will influence the time during which return on microbes’ investment in exo-enzyme production can be realized. Further, if exo-enzyme degradation rates vary across exo-enzymes, microbial investment returns may vary by element across time. We quantify how aging of two soil organic matter (SOM)-decaying enzymes (β-D-cellobioside, BGase; and N-acetyl-β-D-glucosaminide, NAGase) influences enzyme-substrate Vmax at multiple temperatures (5, 15, 25 °C), and compute how enzyme age influences relative availabilities of C and N. Both BGase and NAGase exhibited similar, exponential declines in catalytic rate with age at 25 °C (0.22 ± 0.02 and 0.36 ± 0.14 d−1, respectively). At 15 °C, NAGase exhibited exponential declines in catalytic rates with age (0.79 ± 0.31 d−1), but BGase exhibited no decline. Neither enzyme exhibited a decline in catalytic rate over 72 h at 5 °C. At 15 °C, the amount of C liberated from cellulose and chitin analogues relative to N increased, on average, by more than one order of magnitude. The ratio of C:N liberated from the two substrates remained constant across enzyme age at 25 and 5 °C, but for different reasons: no differences in decay rate across enzymes at 25 °C, and no observed decay at 5 °C. Thus, temperature-dependent decreases of catalytic activity over time may influence microbial resource allocation strategies and rates of SOM decomposition. Because the enzyme decay rates we observed differ considerably from values assumed in most models, such assumptions should be revisited when parameterizing microbial process models.

Keywords

Exo-enzymes Soil organic matter decay Enzyme kinetics Microbial process models 

Funding information

Funder NameGrant NumberFunding Note
National Science Foundation
  • DEB-0950095
  • EAR-1331846

Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  • Sharon Billings
    • 1
  • K. Min
    • 1
  • F. BallantyneIV
    • 2
  • Y. Chen
    • 1
  • M. Sellers
    • 1
  1. 1.University of KansasLawrenceUSA
  2. 2.University of GeorgiaAthensUSA

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