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Meghrazi, Mohammadjavad

University of British Columbia

Adaptations that involve the production of new structures or that require energy expenditure divert resources from cell reproduction, but it is unclear how this metabolic cost is affected by environmental conditions and genetic background. Energy allocation or ribosome allocation frameworks have been previously used to investigate the cost of adaptations. They implicitly assume energy provisioning or protein translation are the limiting pathways in biomass accumulation, respectively, but the connection between them remains poorly understood. Here we suggest these two limitations are specific cases of a more general limitation in the uptake and processing of food and nutrients (provisioning) and converting them to macromolecules (biosynthesis). We connect these two frameworks by showing how limitations in provisioning and biosynthesis simultaneously affect biomass accumulation. To achieve this goal, we reformulate previous models to focus on a trade-off that cells face between the production of biosynthesis machinery and the other proteins required to supply the biosynthesis machinery (provisioning machinery). We incorporate the degradation, recycling, and energetic demands of maintenance into our model and show how these processes affect the observed relationship between the fraction of ribosomes in the proteome and growth rate (also known as bacterial growth laws) during both slow and fast growth. We then use this framework to investigate the relationship between the environmental conditions and the cost of adaptations. We show that the ability of cells to adjust the ratio of provisioning and biosynthetic machinery results in different relationships between the costs of different kinds of adaptations and the environment quality. Notably, adaptations that involve diverting biosynthesis towards the production of new structures are more costly when cells are growing in a high-quality environment, while the cost of adaptations that involve energy expenditure or a higher degradation rate depends on the relative efficiencies of provisioning and biosynthetic machinery. Our results have implications for the effect of environmental conditions on the evolution of resistance to stressors.

Text

2024-04-17

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87863

Zoology

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/