Table 1.
Microbial cell stoichiometries, cell sizes and enzyme production rates used for the evaluation of the effect of life-history traits on resource competition (Fig. 4)
| Parameter | Description | r-strategist (bacteria) | Generalist (bact/fungi) | K-strategist (fungi) | Unit |
|---|---|---|---|---|---|
| Cell stoichiometry* | Cell component | Fraction of cell biomass | |||
| Cell DOM | Cell solubles, immediately available for uptake by other microbes upon cell death (C : N ratio = 15) | 0.06 | 0.06 | 0.06 | |
| Cell MR-C | C-rich microbial remains, i.e. cell wall compounds, lipids, starch (C : N ratio = 150) | 0.78 | 0.52 | 0.37 | |
| Cell MR-N | N-rich microbial remains, i.e. proteins, DNA, RNA (C : N ratio = 5) | 0.16 | 0.42 | 0.57 | |
| Resulting cell C : N ratio | 6.21 | 9.03 | 12.22 | ||
| Cell size and turnover rates† | Fast | Slow | |||
| Max cell size | Size at which a microbial cell divides and colonises a neighbouring microsite | 10 | 100 | fmol C | |
| Max cells ms | Max. number of microbes of that group in one microsite | 3 | 1 | ||
| Enzyme production | Half | Full | |||
| Enz fract | Fraction of microbial C uptake after deduction of maintenance respiration that is invested in enzyme production | 0.06 | 0.12 | ||
| Enz ratio | Ratio in which specific enzymes are produced for the degradation of plant material: C-rich microbial remains: N-rich microbial remains | 0.7: 0.15: 0.15 | 0.7: 0.15: 0.15 | ||
Cell stoichiometries presented here have also been used as assumptions for the three distinct functional groups used in the Bayesian calibration of the model.
Chemical composition of prokaryotic and eukaryotic (e.g. yeast) cells based on Kirchman (2012).
Microbial cell sizes based on Rutz & Kieft (2004); Clode et al. (2009); Bryan et al. (2010); Romanova & Sazhin (2010). Turnover rates are cell size dependent because: (1) growth is related to cell size based on the assumption that uptake is surface dependent and smaller cells have a larger surface to volume ratio, i.e. smaller cells grow relatively faster compared to larger cells. (2) Mortality rate is inversely linked to maximum biomass per microsite, assuming that larger cells invest more in defensive structures. For more details, see Appendix S1.