Fig 1.
Simplified diagram of the growth of filamentous fungi on solid substrates.
The different types of hyphae present are indicated.
Fig 2.
Description of a non-septate reproductive hypha as a series of well-mixed tanks.
Phenomena are denoted by capital letters: (i) Nutrient is provided by the vegetative hypha (tank 0) at the base of the reproductive hypha (tanks 1 to n) and moves towards the tip (tank n) by diffusion between the tanks and convective flow of the cytoplasm. This convective flow is due to evaporation at the hyphal tip; (ii) In the vesicle-producing zone (tanks i+1 to n-1), nutrient is used to produce vesicles containing cell wall precursors; (iii) The vesicles move towards the tip with a fixed velocity (i.e. there is no diffusive contribution to their transport) that can be different from that of the cytoplasm; (iv) The tip (tank n) extends due to the absorption of vesicles.
Table 1.
Values of parameters and initial values of variables.
Table 2.
Sensitivity to the model parameters of the final hyphal length reached at 24 h by Rhizopus oligosporus.
Fig 3.
Temporal profile for hyphal extension predicted by the calibrated model.
The initial values of the variables and the parameter values are as listed in Table 1. Key: (—) Model predictions; (×) Experimental data. (A) Growth of a sporangiophore of Rhizopus oligosporus, data from Nopharatana et al. [13]; (B) Growth of a tall conidiophore of Aspergillus giganteus, data from Trinci and Banbury [14]; (C) Growth of a sporangiophore of Phycomyces blakesleeanus, data from Gruen [15]. In this particular case, zero time and zero length correspond to 20 h and the hyphal length at 20 h, respectively, in the graph of Gruen [15].
Fig 4.
Model predictions for spatial profiles of nutrient and vesicles at different times for Rhizopus oligosporus.
(A) Nutrient concentration; (B) Concentration of vesicles. The time of each spatial profile is indicated directly on the graph. The initial values of the variables and the parameter values are as listed in Table 1.
Fig 5.
Comparison of the model predictions about vesicle distribution near the tip with experimental data.
Model predictions are for 24 h of cultivation, from the simulation done for Rhizopus oligosporus. Experimental studies of Collinge and Trinci [8] and Gooday [37] were used for comparison. The experimental data are plotted based on segments of 10 μm length, in order to enable a comparison with the last five tanks of the model.
Fig 6.
Effect of the concentration of nutrients in the source tank (ω0).
The comparison is based on the hyphal length reached at 24 h. The original value (i.e. that used for Figs. 3A and 4) is indicated with an arrow. The initial values of the variables and the other parameter values are as listed for Rhizopus oligosporus in Table 1.
Fig 7.
Effect of the maintenance coefficient (m).
The comparison is based on the hyphal length reached at 24 h. The original value (i.e. that used for Figs. 3A and 4) is indicated with an arrow. The initial values of the variables and the other parameter values are as listed for Rhizopus oligosporus in Table 1.
Fig 8.
Effect of the maximum rate of vesicle production (kp).
The comparison is based on the hyphal length reached at 24 h. The original value (i.e. that used for Figs. 3A and 4) is indicated with an arrow. The initial values of the variables and the other parameter values are as listed for Rhizopus oligosporus in Table 1.
Fig 9.
Effect of the convective flow velocity within the hypha (v).
The comparison is based on the hyphal length reached at 24 h. The original value (i.e. that used for Figs. 3A and 4) is indicated with an arrow. The initial values of the variables and the other parameter values are as listed for Rhizopus oligosporus in Table 1.