The form of a trade‐off determines the response to competition

Abstract

Understanding how populations and communities respond to competition is a central concern of ecology. A seminal theoretical solution first formalised by Levins (and re-derived in multiple fields) showed that, in theory, the form of a trade-off should determine the outcome of competition. While this has become a central postulate in ecology it has evaded experimental verification, not least because of substantial technical obstacles. We here solve the experimental problems by employing synthetic ecology. We engineer strains of Escherichia coli with fixed resource allocations enabling accurate measurement of trade-off shapes between bacterial survival and multiplication in multiple environments. A mathematical chemostat model predicts different, and experimentally verified, trajectories of gene frequency changes as a function of condition-specific trade-offs. The results support Levins' postulate and demonstrates that otherwise paradoxical alternative outcomes witnessed in subtly different conditions are predictable.

Stress-Induced Mutation Rates Show a Sigmoidal and Saturable Increase Due to the RpoS Sigma Factor in Escherichia coli

“…We recently constructed a set of synthetic strains to achieve fixed, environment-independent RpoS levels (Maharjan et al 2013). The strains in the set do not have transcriptional, translational, and post-translational control over RpoS levels; instead these strains contain distinct synthetic promoters to express fixed levels of rpoS.…”

“…The strains in the set do not have transcriptional, translational, and post-translational control over RpoS levels; instead these strains contain distinct synthetic promoters to express fixed levels of rpoS. All the strains along with their RpoS level are listed in Table 1 and were standardized to the content of RpoD, which is constant in different environments (Ishihama 2000;Gutierrez et al 2013;Maharjan et al 2013). The strain set covered a 200-fold range of sigma factor ratios and expressed the full range of environmental stress resistance phenotypes controlled by the general stress response (Maharjan et al 2013).…”

“…All the strains along with their RpoS level are listed in Table 1 and were standardized to the content of RpoD, which is constant in different environments (Ishihama 2000;Gutierrez et al 2013;Maharjan et al 2013). The strain set covered a 200-fold range of sigma factor ratios and expressed the full range of environmental stress resistance phenotypes controlled by the general stress response (Maharjan et al 2013). The RpoS/RpoD ratios in the synthetic strains (BW5205-BW5222) remain relatively constant in different growth phases, unlike the wild-type MC4100, as shown in Table 1.…”

“…The RpoS/RpoD ratios in the synthetic strains (BW5205-BW5222) remain relatively constant in different growth phases, unlike the wild-type MC4100, as shown in Table 1. To check whether different cultures of strains maintained similar RpoS levels, we tested iodine staining levels of cultures using the method that we used in our previous study; iodine staining is linearly dependent on the RpoS content of cells (Maharjan et al 2013). There was no change in staining level in cultures suggesting that storage and repeat culture did not affect the RpoS levels.…”

“…So for both the Cyc R and Rif R assays, the low-RpoS strain reflects previously obtained lab data, but the high-RpoS strain is closer to the SIM state. a RpoS/RpoD ratio data for the two culture conditions are from graphs in Maharjan et al (2013) based on Western blot analysis of RpoS and RpoD detected using anti-RpoS and anti-RpoD antibodies. The mean (m) and standard deviation (SD) were from at least three independent experiments.…”