Both phenotypic and genotypic adaptation of E. coli to thermal stress is contingent on genetic background

Here, we performed the second phase of a two-phase evolution experiment using Escherichia coli that were previously adapted to the stressful temperature of 42.2C during the first phase of evolution to study contingency in evolution. The Phase 1 evolved lines had evolved through two adaptive pathways: mutation of rpoB, encoding RNA polymerase, or through rho, a transcriptional terminator. Using 10 different E. coli Founders representing both adaptive pathways, we performed a second phase of evolution at 19.0C to investigate how prior genetic divergence or adaptive history (rpoB vs. rho) may affect the likelihood of parallel responses and evolutionary outcomes. This project has the whole genome sequencing reads of the Phase 2 evolved populations.