Transport-limited reactions in microbial systems

Area of Science:

• Microbial Ecology
• Biogeochemistry
• Environmental Science

Background:

• Predicting microbial metabolic rates and biogeochemical fluxes is complex due to unknown parameters and species composition.
• Current models often require extensive data on population dynamics, physiology, and kinetics, limiting their applicability.

Purpose of the Study:

• To demonstrate that microbial process predictions can be made without detailed kinetic or species information.
• To introduce and validate the 'fast-reaction-transport' (FRT) limit for microbial biogeochemistry.

Main Methods:

• Utilized a 'fast-reaction-transport' (FRT) framework, which assumes reaction kinetics operate on shorter timescales than physical transport.
• Applied the FRT approach to long-term time-series data (2001-2014) from the anoxic Cariaco Basin (180-900m depth).
• Focused on chemical boundary conditions, physical mixing, and reaction stoichiometries, omitting species composition and kinetic parameters.

Main Results:

• The FRT approach accurately predicted the dynamics of major electron donors and acceptors (Pearson r ≥ 0.9).
• Demonstrated that microbial processes in the Cariaco Basin are predominantly transport-limited.
• Showed predictability of biogeochemical fluxes irrespective of microbial species composition, population dynamics, and kinetics.

Conclusions:

• The FRT limit provides a powerful, data-efficient method for predicting microbial biogeochemical fluxes in poorly mixed environments.
• This approach is applicable to numerous systems where microbial community details are unknown.
• Findings suggest a mechanism for the observed decoupling between microbial function and taxonomy.