Project description:Selection of drug-resistant mammalian cell mutants requires multiple drug exposures. Since cells in starting population could be genetically identical, selection of pre-existent mutations is unlikely. Therefore, adaptation must involve generation of drug-resistant mutations de-novo. Understanding how adaptive mutations are generated and protect cells is important for our knowledge of cancer biology and evolution. Here, we studied adaptation of cancer cells to topoisomerase (Top1) inhibitor irinotecan, which triggers DNA breaks, resulting in cytotoxicity. Resistance mechanism was based on gradual accumulation of recurrent mutations in non-coding DNA at sequence-specific Top1 cleavage sites. Repair of DSBs at these sites following initial irinotecan exposures created mutant sequences that were resistant to further Top1 cleavage. Therefore, by virtue of creating DNA breaks Top1 increases the rate of highly protective mutations specifically at such spots, thus explaining a puzzling need of dose escalation in resistance development.
Project description:This study demonstrates simulated microgravity effects on E. coli K 12 MG1655 when grown on LB medium supplemented with glycerol. The results imply that E. coli readily reprograms itself to combat the multiple stresses imposed due to microgravity. Under these conditions it survives by upregulating oxidative stress protecting genes and simultaneously down regulating the membrane transporters and synthases to maintain cell homeostasis.
Project description:Ten populations were evolved for 6,000 generations. Five had strong selection for sporulation, imposed partially by their cultivation in sporulation-inducing medium, while the other five populations had relaxed selection for sporulation, by cultivating them in sporulation-repressing medium. Batch cultures were diluted 1:100 daily for approximately 892 days. In the five populations with relaxed selection for sporulation, sporulation ability was eventually lost. Keywords: comparative genome hybridization and transcriptome divergence
Project description:This study demonstrates simulated microgravity effects on E. coli K 12 MG1655 when grown on LB medium supplemented with glycerol. The results imply that E. coli readily reprograms itself to combat the multiple stresses imposed due to microgravity. Under these conditions it survives by upregulating oxidative stress protecting genes and simultaneously down regulating the membrane transporters and synthases to maintain cell homeostasis. In this study, a clinostat that mimics microgravity conditions was used to investigate the effects of microgravity on E. coli grown in LB medium supplemented with glycerol to monitor the effects on growth and global gene expression using Affymetrix DNA microarrays.
Project description:Hybrid progeny can enjoy increased fitness and stress tolerance relative to their ancestral species, a phenomenon known as hybrid vigor. Though this phenomenon has been documented throughout the Eukarya, evolution of hybrid populations has yet to be explored experimentally in the lab. To fill this knowledge gap we created a pool of Saccharomyces cerevisiae and S. bayanus homoploid and aneuploid hybrids, and then investigated how selection in the form of incrementally increased temperature or ethanol impacted hybrid genome structure and adaptation. During 500 generations of continuous ammonia-limited, glucose-sufficient culture, temperature was raised from 25C to 46??C. This selection invariably resulted in nearly-complete loss of the S. bayanus genome, although the dynamics of genome loss differed among independent replicates. Temperature-evolved isolates were significantly more thermal tolerant and exhibited greater phenotypic plasticity than parental species and founding hybrids. By contrast, when the same hybrid pool was subjected to increases in exogenous ethanol from 0% to 14%, selection favored euploid S. cerevisiae x S. bayanus hybrids. Ethanol-evolved isolates exhibited significantly greater ethanol tolerance relative only to S. bayanus and one of the founding hybrids tested. Adaptation to thermal and ethanol stress manifested as heritable changes in cell wall structure demonstrated by resistance to zymolyase or micafungin treatment. This is the first study to show experimentally that the fate of interspecific hybrids critically depends on the type of selection they encounter during the course of evolution.
Project description:To study the dynamics of acid adaptation in E.coli at pH5.5 as opposed to that at pH7, samples were collected from a steady-state system for transcriptomics. Keywords: time course
Project description:To study the dynamics of acid adaptation in E.coli at pH5.5 as opposed to that at pH7, samples were collected from a steady-state system for transcriptomics. Keywords: time course
