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Microbial evolution. Global epistasis makes adaptation predictable despite sequence-level stochasticity.

ABSTRACT: Epistatic interactions between mutations can make evolutionary trajectories contingent on the chance occurrence of initial mutations. We used experimental evolution in Saccharomyces cerevisiae to quantify this contingency, finding differences in adaptability among 64 closely related genotypes. Despite these differences, sequencing of 104 evolved clones showed that initial genotype did not constrain future mutational trajectories. Instead, reconstructed combinations of mutations revealed a pattern of diminishing-returns epistasis: Beneficial mutations have consistently smaller effects in fitter backgrounds. Taken together, these results show that beneficial mutations affecting a variety of biological processes are globally coupled; they interact strongly, but only through their combined effect on fitness. As a consequence, fitness evolution follows a predictable trajectory even though sequence-level adaptation is stochastic.

SUBMITTER: Kryazhimskiy S

PROVIDER: S-EPMC4314286 | biostudies-literature | 2014 Jun

REPOSITORIES: biostudies-literature

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Microbial evolution. Global epistasis makes adaptation predictable despite sequence-level stochasticity.

Kryazhimskiy Sergey S Rice Daniel P DP Jerison Elizabeth R ER Desai Michael M MM

Science (New York, N.Y.) 20140601 6191

Epistatic interactions between mutations can make evolutionary trajectories contingent on the chance occurrence of initial mutations. We used experimental evolution in Saccharomyces cerevisiae to quantify this contingency, finding differences in adaptability among 64 closely related genotypes. Despite these differences, sequencing of 104 evolved clones showed that initial genotype did not constrain future mutational trajectories. Instead, reconstructed combinations of mutations revealed a patter ...[more]

PMID: 24970088

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Project description:AIM OF THE STUDY: In many countries, Low Level Disinfection (LLD) of covered transvaginal ultrasound probes is recommended between patients' examinations. The aim of this study was to evaluate the antimicrobial efficacy of LLD under routine conditions on a range of microorganisms. MATERIALS AND METHODS: Samples were taken over a six month period in a private French Radiology Center. 300 specimens derived from endovaginal ultrasound probes were analyzed after disinfection of the probe with wipes impregnated with a quaternary ammonium compound and chlorhexidine. Human papillomavirus (HPV) was sought in the first set of s100 samples, Chlamydia trachomatis and mycoplasmas were searched in the second set of 100 samples, bacteria and fungi in the third 100 set samples. HPV, C. trachomatis and mycoplasmas were detected by PCR amplification. PCR positive samples were subjected to a nuclease treatment before an additional PCR assay to assess the likely viable microorganisms. Bacteria and fungi were investigated by conventional methods. RESULTS: A substantial persistence of microorganisms was observed on the disinfected probes: HPV DNA was found on 13% of the samples and 7% in nuclease-resistant form. C. trachomatis DNA was detected on 20% of the probes by primary PCR but only 2% after nuclease treatment, while mycoplasma DNA was amplified in 8% and 4%, respectively. Commensal and/or environmental bacterial flora was present on 86% of the probes, occasionally in mixed culture, and at various levels (10->3000 CFU/probe); Staphylococcus aureus was cultured from 4% of the probes (10-560 CFU/probe). No fungi were isolated. CONCLUSION: Our findings raise concerns about the efficacy of impregnated towels as a sole mean for disinfection of ultrasound probes. Although the ultrasound probes are used with disposable covers, our results highlight the potential risk of cross contamination between patients during ultrasound examination and emphasize the need for reviewing the disinfection procedure.

Dataset Information

Microbial evolution. Global epistasis makes adaptation predictable despite sequence-level stochasticity.

Publications

Microbial evolution. Global epistasis makes adaptation predictable despite sequence-level stochasticity.

Similar Datasets

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