EVOLUTION OF INTRINSIC GROWTH RATE: METABOLIC COSTS DRIVE TRADE-OFFS BETWEEN GROWTH AND SWIMMING PERFORMANCE IN MENIDIA MENIDIA

AbstractIn nature, organisms are simultaneously exposed to multiple stresses (i.e. complex environments) that often fluctuate unpredictably. While both these factors have been studied in isolation, the interaction of the two remains poorly explored. To address this issue, we selected laboratory populations ofEscherichia coliunder complex (i.e. stressful combinations of pH, H2O2and NaCl) unpredictably fluctuating environments for ~900 generations. We compared the growth rates and the corresponding trade-off patterns of these populations to those that were selected under constant values of the component stresses (i.e. pH, H2O2and NaCl) for the same duration. The fluctuation-selected populations had greater mean growth rate and lower variation for growth rate over all the selection environments experienced. However, while the populations selected under constant stresses experienced severe tradeoffs in many of the environments other than those in which they were selected, the fluctuation-selected populations could by-pass the across-environment trade-offs completely. Interestingly, trade-offs were found between growth rates and carrying capacities. The results suggest that complexity and fluctuations can strongly affect the underlying trade-off structure in evolving populations.

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Qualitative Analysis of the Effect of Weeds Removal in Paddy Ecosystems in Fallow Season

Discrete Dynamics in Nature and Society ◽

10.1155/2020/8716314 ◽

2020 ◽

Vol 2020 ◽

pp. 1-12

Author(s):

Leru Zhou ◽

Zhigang Liu ◽

Tiejun Zhou

Keyword(s):

Growth Rate ◽

Equilibrium State ◽

Excretion Rate ◽

Critical Value ◽

Inorganic Fertilizer ◽

Paddy Fields ◽

Asymptotically Stable ◽

Intrinsic Growth Rate ◽

Stable Conditions ◽

Coexistence Equilibrium

In the paper, we introduce a differential equations model of paddy ecosystems in the fallow season to study the effect of weeds removal from the paddy fields. We found that there is an unstable equilibrium of the extinction of weeds and herbivores in the system. When the intensity of weeds removal meets certain conditions and the intrinsic growth rate of herbivores is higher than their excretion rate, there is a coexistence equilibrium state in the system. By linearizing the system and using the Routh–Hurwitz criterion, we obtained the local asymptotically stable conditions of the coexistence equilibrium state. The critical value formula of the Hopf bifurcation is presented too. The model demonstrates that weeds removal from paddy fields could largely reduce the weeds biomass in the equilibrium state, but it also decreases the herbivore biomass, which probably reduces the content of inorganic fertilizer in the soil. We found a particular intensity of weeds removal that could result in the minimum content of inorganic fertilizer, suggesting weeds removal should be kept away from this intensity.

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Massive Phenotypic Measurements Reveal Complex Physiological Consequences of Differential Translation Efficacies

10.1101/209098 ◽

2017 ◽

Cited By ~ 1

Author(s):

Adam Paul Arkin ◽

Guillaume Cambray

Keyword(s):

Growth Rate ◽

Translation Initiation ◽

Protein Production ◽

Protein Biosynthesis ◽

Cellular Growth ◽

Sequence Variants ◽

Release Rates ◽

Trade Offs ◽

Fluctuating Environments ◽

Protein Overproduction

ABSTRACTControl of protein biosynthesis is at the heart of resource allocation and cell adaptation to fluctuating environments. One gene’s translation often occurs at the expense of another’s, resulting in global energetic and fitness trade-offs during differential expression of various functions. Patterns of ribosome utilization—as controlled by initiation, elongation and release rates—are central to this balance. To disentangle their respective determinants and physiological impacts, we complemented measurements of protein production with highly parallelized quantifications of transcripts’ abundance and decay, ribosome loading and cellular growth rate for 244,000 precisely designed sequence variants of an otherwise standard reporter. We find highly constrained, non-monotonic relationships between measured phenotypes. We show that fitness defects derive either from protein overproduction, with efficient translation initiation and heavy ribosome flows; or from unproductive ribosome sequestration by highly structured, slowly initiated and overly stabilized transcripts. These observations demonstrate physiological impacts of key sequence features in natural and designed transcripts.

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