Project description:The hypothesis that increased fitness within a selective environment must be accompanied by a loss of fitness in other non-selective environments leads to the notion of evolutionary tradeoffs. Experimental evolution provides an approach to test the existence of evolutionary tradeoffs, characterize their general quality, and reveal their genetic origins. To examine the underlying mechanism for a fitness trade-off, we constructed the evolutionary trajectories of Escherichia coli K-12 at increasing temperatures up to 45.3°C, and found diverging mutational histories that led to adaptive phenotypes with and without fitness trade-offs at low temperatures. We identified genetic changes in cellular respiration, iron metabolism and methionine biosynthesis that regulated gene expression to achieve thermal adaptation and determined the presence and absence of a fitness trade-off. Our results suggested that evolutionary trade-off could be generated by a regulatory protein mutation that was beneficial in the selective conditions but forced suboptimal proteome allocation under non-selective environments.
Project description:The transcriptome and DGE analysis of the fat body and ovary of L. migratoria based on the Illumina short-read sequencing technology and De novo assembly. Research on the trade-offs between immunity and reproduction is contributing significantly to the understanding of the fitness of organisms in nature.
Project description:The transcriptome and DGE analysis of the fat body and ovary of L. migratoria based on the Illumina short-read sequencing technology and De novo assembly. Research on the trade-offs between immunity and reproduction is contributing significantly to the understanding of the fitness of organisms in nature. The cDNA libraries for the mixed tissue samples of the fat body and ovary collected from the Sephadex group, the bacterial parasite group, and the dipteran parasite group at 4 hours and 6 days post-treatment were made for the DGE analysis. Every experimental treatment sample had one DGE-seq and one parallel replication.
Project description:Plasmid fitness is directed by two orthogonal processes—vertical transfer through cell division and horizontal transfer through conjugation. When considered individually, improvements in either mode of transfer can promote how well a plasmid spreads and persists. Together, however, the metabolic cost of conjugation could create a tradeoff that constrains plasmid evolution. Here we present evidence for the presence, consequences, and molecular basis of a conjugation-growth tradeoff across 40 plasmids derived from clinical E. coli pathogens. We discover that most plasmids operate below a conjugation efficiency threshold for major growth effects, indicating strong natural selection for vertical transfer. Below this threshold, E. coli demonstrates a remarkable growth tolerance to over four orders of magnitude change in conjugation efficiency. This tolerance fades as nutrients become scarce and horizontal transfer attracts a greater share of host resources. Our results provide insight into evolutionary constraints directing plasmid fitness and strategies to combat the spread of antibiotic resistance.
Project description:Exploring molecular details of carbon utilization trade-offs in galactose-evolved yeast Adaptively evolved yeast mutants on galactose for around 400 generations showed diminished growth and carbon uptake rates on glucose. Genome-scale approaches were applied to characterize the molecular genetic basis of these trade-offs in carbon source utilization. Engineered mutants showing trade-offs in a specific carbon uptake rate between both carbons were used as controls. The transcriptional responses of the evolved mutants were almost identical during growth on both carbon sources. These carbon-independent conserved patterns were clearly observed in specific pathways and genes. Up-regulation of PGM2, a confirmed beneficial genetic change for improving galactose utilization was preserved on both carbons. In addition, HXK1, GLK1 and genes involved in reserve carbohydrate metabolism were up-regulated, while HXK2 was down-regulated. Genes that have a transcription factor binding site for Gis1p, Rph1p, Msn2/4p and Nrg1p were up-regulated. These results indicated changes in the metabolic pathways involved in metabolism of both carbons and in nutrient signaling pathway. The concentration profile of trehalose and glycogen supported these findings. Mutations in RAS2 and ERG5 genes were selected because of their beneficial and neutral effect on galactose utilization, respectively in our previous study. Site-directed mutants containing galactose-beneficial mutations in RAS2 only resulted in a significant decrease in glucose utilization. Integration of all these analyses clearly suggest an antagonistic pleiotropic trade-off in carbon source utilization caused by changes in regulatory region, and we hereby demonstrate how systems biology can be used to gain insight into evolutionary processes at the molecular level. Yeast galactose evolved mutants having improved galactose availability were grown on aerobic batch with glucose as carbon source
Project description:The multidrug resistance-encoding plasmids belonging to the IncA/C incompatibility group have recently emerged among Escherichia coli and Salmonella enterica in the United States. These plasmids have a unique genetic structure compared to other enterobacterial plasmid types, a broad host range, and propensity to acquire large numbers of antimicrobial resistance genes via their accessory regions. Using E. coli strain DH5α harboring the prototype IncA/C plasmid pAR060302, we sought to define the baseline transcriptome of IncA/C plasmids under laboratory growth and in the face of selective pressure. The effects of ampicillin, florfenicol or streptomycin exposure were compared to cells left untreated at logarithmic phase using Illumina sequencing (RNA-Seq). Under growth in Luria-Bertani broth lacking antibiotics, much of the backbone of pAR060302 was transcriptionally inactive, including its putative transfer regions. A few plasmid backbone genes of interest were highly transcribed, including genes of a putative toxin-antitoxin system and an H-NS-like transcriptional regulator. In contrast, numerous genes within the accessory regions of pAR060302 were highly transcribed, including the resistance genes floR, blaCMY-2, aadA, and aacA. Antibiotic treatment with ampicillin or streptomycin resulted in no genes being differentially expressed compared to controls lacking antibiotics, suggesting that many of the resistance-associated genes are not differentially expressed due to exposure to these antibiotics. In contrast, florfenicol treatment resulted in the up-regulation of floR and numerous chromosomally encoded genes. Overall, the transcriptome mapping of pAR060302 suggests that it mitigates the fitness costs of carrying resistance-associated genes through global regulation with its transcriptional regulators.
Project description:Genomic Characterization of Adaptive Mutations that Effect Minimal Fitness Trade-offs in Evolved Clones of Saccharomyces cerevisiae
Project description:Exploring molecular details of carbon utilization trade-offs in galactose-evolved yeast Adaptively evolved yeast mutants on galactose for around 400 generations showed diminished growth and carbon uptake rates on glucose. Genome-scale approaches were applied to characterize the molecular genetic basis of these trade-offs in carbon source utilization. Engineered mutants showing trade-offs in a specific carbon uptake rate between both carbons were used as controls. The transcriptional responses of the evolved mutants were almost identical during growth on both carbon sources. These carbon-independent conserved patterns were clearly observed in specific pathways and genes. Up-regulation of PGM2, a confirmed beneficial genetic change for improving galactose utilization was preserved on both carbons. In addition, HXK1, GLK1 and genes involved in reserve carbohydrate metabolism were up-regulated, while HXK2 was down-regulated. Genes that have a transcription factor binding site for Gis1p, Rph1p, Msn2/4p and Nrg1p were up-regulated. These results indicated changes in the metabolic pathways involved in metabolism of both carbons and in nutrient signaling pathway. The concentration profile of trehalose and glycogen supported these findings. Mutations in RAS2 and ERG5 genes were selected because of their beneficial and neutral effect on galactose utilization, respectively in our previous study. Site-directed mutants containing galactose-beneficial mutations in RAS2 only resulted in a significant decrease in glucose utilization. Integration of all these analyses clearly suggest an antagonistic pleiotropic trade-off in carbon source utilization caused by changes in regulatory region, and we hereby demonstrate how systems biology can be used to gain insight into evolutionary processes at the molecular level.