Project description:To understand the mechanism of isopropanol tolerance of Escherichia coli for improvement of isopropanol production, we performed genome re-sequencing and transcriptome analysis of isopropanol tolerant E. coli strains obtained from parallel adaptive laboratory evolution under IPA stress.
Project description:Substrains in Escherichia coli K-12 MG1655 can possess various swimming motility, which is mostly resulted from different expression levels of flhDC. Here, we studied the swimming motility of two MG1655 substrains, CY562 and CY570. Our results showed that CY562 had no insertion at the promoter region of flhDC and possessed no swimming motility. In contrast, CY570 had an IS-element insertion at the promoter region of flhDC and showed a hyper-motile phenotype. Transcriptomic data suggest that expression of flhDC and the other known flagella genes was much lower in CY562 than that in CY570. Moreover, CY562 possessed higher expression levels for genes involved in stress response, especially acid-stress response, than CY570. Consistently, CY562 showed a higher survival rate under acid stress than CY570. Our data indicate that there are mechanisms conversely regulating motility and stress response in E. coli.
Project description:To overcome the inhibition caused by the fermentation supernatant in the late fermentation stage of docosahexaenoic acid (DHA)-producing Crypthecodinium cohnii, fermentation supernatant-based adaptive laboratory evolution (FS-ALE) was conducted. The cell growth and DHA productivity of the evolved strain (FS280) obtained after 280 adaptive cycles corresponding to 840 days of evolution were increased by 161.87% and 311.23%, respectively, at 72 h under stress conditions and increased by 19.87% and 51.79% without any stress compared with the starting strain, demonstrating the effectiveness of FS-ALE.
Project description:Using a synthetic biosensor to couple production of a specific metabolite with cell growth, we spontaneously evolved cells under the selective condition toward the acquisition of genotypes that optimally reallocated cellular resources. Using 3-hydroxypropionic acid (3-HP) production from glycerol in Escherichia coli as a model system, we determined that spontaneous mutations in the conserved regions of proteins involved in global transcriptional regulation altered the expression of several genes associated with central carbon metabolism. Our study provides a new perspective on adaptive laboratory evolution (ALE) using synthetic biosensors, thereby supporting future efforts in metabolic pathway optimization.
