Fig. 3
Simulation results for division of labour (DOL) compared to single-cell co-expression. Our proposed model accounts for the number of free ribosomes (free), and the number of ribosomes engaged in translation (cx) for the production of different types of protein (x, where x is ea, heterologous protein A; eb, heterologous protein B; q, housekeeping protein; em, metabolic enzyme; et, transport enzyme; r, ribosomal protein). Two heterologous proteins, ea and eb, can be expressed in a monoculture or consortium. Considering maximum transcription rates (ω) of 20 mRNA/min for both proteins, we use this model to predict the steady-state amount of ribosomes dedicated to the translation of these proteins and the associated cell growth rate that results from the reallocation of these ribosomes. a In monoculture at steady state 16.3% of ribosomes are diverted to heterologous expression with an associated doubling time of 44 min. b DOL in a two-strain consortium means the resources of each cell are only diverted to the expression of a single protein. The overall reallocation of ribosomes to heterologous expression is thus reduced. However, the fraction of ribosomes allocated to the translation of each protein type is higher in the consortium case (ea: 9.2%, eb: 10.1% in the consortium case, compared to 7.5% and 8.8%, respectively in the monoculture case). The doubling time is faster compared to the monoculture case, while the number of heterologous proteins of each type produced per cell is higher. c In monoculture, the growth rate (λ) is dependent on the maximum transcription rates (ω) of both heterologous proteins. In the consortium, the growth rate is dependent on only one of the two transcription rates. ea & eb: two generic heterologous proteins, cx: ribosome:mRNA complexes for protein x (x ∈ {ea, eb, q, em, et, r}), λ: growth rate, ωea: maximum transcription rate of ea, ωeb: maximum transcription rate of eb