Dataset Information

Escherichia coli with a Tunable Point Mutation Rate for Evolution Experiments.

ABSTRACT: The mutation rate and mutations' effects on fitness are crucial to evolution. Mutation rates are under selection due to linkage between mutation rate modifiers and mutations' effects on fitness. The linkage between a higher mutation rate and more beneficial mutations selects for higher mutation rates, while the linkage between a higher mutation rate and more deleterious mutations selects for lower mutation rates. The net direction of selection on mutations rates depends on the fitness landscape, and a great deal of work has elucidated the fitness landscapes of mutations. However, tests of the effect of varying a mutation rate on evolution in a single organism in a single environment have been difficult. This has been studied using strains of antimutators and mutators, but these strains may differ in additional ways and typically do not allow for continuous variation of the mutation rate. To help investigate the effects of the mutation rate on evolution, we have genetically engineered a strain of Escherichia coli with a point mutation rate that can be smoothly varied over two orders of magnitude. We did this by engineering a strain with inducible control of the mismatch repair proteins MutH and MutL. We used this strain in an approximately 350 generation evolution experiment with controlled variation of the mutation rate. We confirmed the construct and the mutation rate were stable over this time. Sequencing evolved strains revealed a higher number of single nucleotide polymorphisms at higher mutations rates, likely due to either the beneficial effects of these mutations or their linkage to beneficial mutations.

SUBMITTER: Sherer NA

PROVIDER: S-EPMC7407472 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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<i>Escherichia coli</i> with a Tunable Point Mutation Rate for Evolution Experiments.

Sherer Nicholas A NA Kuhlman Thomas E TE

G3 (Bethesda, Md.) 20200805 8

The mutation rate and mutations' effects on fitness are crucial to evolution. Mutation rates are under selection due to linkage between mutation rate modifiers and mutations' effects on fitness. The linkage between a higher mutation rate and more beneficial mutations selects for higher mutation rates, while the linkage between a higher mutation rate and more deleterious mutations selects for lower mutation rates. The net direction of selection on mutations rates depends on the fitness landscape, ...[more]

PMID: 32503807

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Project description:Purpose: To understand how D654Y mutated RpoB affect gene expression under either normal or osmotic stress conditions in Escherichia coli . Methods: RNA-seq libraries were constructed for four samples, including (I) The parental strain Suc-T110 grown at normal condition (5%w/v glucose); (II)RpoB mutant RpoBD645Y [Suc-T110::rpoB (D654Y), RNA-seq library named NZ-502] grown at normal condition;(III) Suc-T110 grown at osmotic stress condition(12%w/v glucose);(IV) NZ-502 grown at osmotic stress condition. For preparation of RNA samples, Fresh colonies were picked from New NBS mineral salts plates containing 20 g liter-1 glucose, inoculated into 250 ml flasks containing 30 ml NBS mineral salts medium with 20 g liter-1 glucose, and grown at 37°C and 250 rpm for 12 h. Cultures were then transferred to a 500 ml fermentation vessel containing 250 ml NBS mineral salts medium with either 5%w/v or 12%w/v glucose. After 48 h, 1 ml culture was harvested by centrifugation, frozen in liquid nitrogen and sent to Beijing Genomics Institute (BGI, Shenzhen, China). The four 90-nt paired-end RNA-seq libraries were generated commercially at Beijing Genomics Institute by using the HiSeq™ 2000 platform. Sequencing data was handled essentially with Bowtie2, NOIseq. Expression levels are presented as Reads Per Kilobase of transcript per Million mapped reads (RPKM). Results: we first comparative accessed expression levels of Suc-T110 and NZ-502 under normal condition. Among the 4200 predicted genes, 128 genes were found altered their expression in NZ502 compared with Suc-T110; with 38 targets specific up-regulated while 90 targets down-regulated. Genes engaged in biological function of amino acid metabolism (P-value=4.60E-05) were significantly enriched among in induced gene set. Under osmotic stress condition, 244 differential expressed genes were identified in NZ-502 when compared with Suc-T110, with 132 targets specific up-regulated while 112 targets down-regulated, Functional enrichment of 132 up regulated genes showed the most significantly enriched physiological function of NZ-502 upon hyperosmotic stress was associated with carbon source transportation (FunCat term: 20.01.03 C-compound and carbohydrate transport, P-value=9.51E-05), which containing a group of genes encoding diverse sugar transporters. Conclusions: Transcriptome profiling suggested that derepression of sugar transporters might be the primary cause for NZ-502 to resist osmotic stress.

Dataset Information

Escherichia coli with a Tunable Point Mutation Rate for Evolution Experiments.

Publications

<i>Escherichia coli</i> with a Tunable Point Mutation Rate for Evolution Experiments.

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