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Linking Cell Size, Vmax and Km in Phototrophs and Chemotrophs: Insights From Bayesian Inference
1Department of Chemistry, Biology, and Environmental Sciences, Nara Women's University, Kita-Uoya Nishimachi, Nara, Japan.
Environmental Microbiology Reports
|June 19, 2025
Summary
Understanding microbial nutrient uptake is key for modeling. This study reveals chemotrophic microbes have higher maximum uptake rates and half-saturation constants than phototrophs, with factors beyond cell size influencing these parameters.
Area of Science:
- Microbial Ecology
- Biogeochemistry
- Physiology
Background:
- Microbial growth modeling relies on understanding resource uptake rates.
- Nutrient uptake in phototrophs is limited by membrane transporters, with cell-specific maximum uptake rate (Vmax) scaling with cell size and showing a trade-off with the half-saturation constant (Km).
- Similar constraints may apply to chemotrophs, but direct cell size data are often lacking.
Purpose of the Study:
- To investigate scaling relationships of nutrient uptake kinetics (Vmax and Km) in chemotrophic microorganisms.
- To compare these relationships with those observed in phototrophic plankton.
- To identify factors influencing nutrient uptake rates in chemotrophs.
Main Methods:
- Assumed log-normal distributions for prokaryotic cell sizes, Vmax, and Km.
- Applied Bayesian analysis to derive scaling exponents.
- Compared kinetic parameters (VmaxDW and Km) between chemotrophs and phototrophs.
Main Results:
- Chemotrophs generally exhibit higher maximum uptake rate per dry weight (VmaxDW) and Km values than phototrophs.
- VmaxDW and Km were not strongly correlated across all chemotroph data.
- Bayesian-derived exponents for VmaxDW and Km exceeded those predicted by simple allometric scaling based on membrane transport capacity.
Conclusions:
- Chemotrophic microbial nutrient uptake kinetics differ from phototrophs, with higher VmaxDW and Km values.
- Factors beyond cell size and membrane transport capacity significantly influence nutrient uptake kinetics in chemotrophs.
- Further research is needed to elucidate the additional factors governing these microbial physiological processes.
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