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7 results on '"Arias-Sánchez, Flor I."'

6. Effects of prior exposure to antibiotics on bacterial adaptation to phages

Author

Arias-Sánchez, Flor I., Allen, Richard C., and Hall, Alex

Subjects
antibiotic dosage, bacteriophages, bacterial adaptation, mutagenesis, 3. Good health
Abstract

Understanding adaptation to complex environments requires information about how exposure to one selection pressure affects adaptation to others. For bacteria, antibiotics and viral parasites (phages) are two of the most common selection pressures and are both relevant for treatment of bacterial infections: increasing antibiotic resistance is generating significant interest in using phages in addition or as an alternative to antibiotics. However, we lack knowledge of how exposure to antibiotics affects bacterial responses to phages. Specifically, it is unclear how the negative effects of antibiotics on bacterial population growth combine with any possible mutagenic effects or physiological responses to influence adaptation to other stressors such as phages, and how this net effect varies with antibiotic concentration. Here, we experimentally addressed the effect of pre‐exposure to a wide range of antibiotic concentrations on bacterial responses to phages. Across 10 antibiotics, we found a strong association between their effects on bacterial population size and subsequent population growth in the presence of phages (which in these conditions indicates phage‐resistance evolution). We detected some evidence of mutagenesis among populations treated with fluoroquinolones and β‐lactams at sublethal doses, but these effects were small and not consistent across phage treatments. These results show that, although stressors such as antibiotics can boost adaptation to other stressors at low concentrations, these effects are weak compared to the effect of reduced population growth at inhibitory concentrations, which in our experiments strongly reduced the likelihood of subsequent phage‐resistance evolution., Journal of Evolutionary Biology, 31 (2), ISSN:1010-061X, ISSN:1420-9101

7. Bacterial and viral adaptation in ecologically complex systems

Author

Arias-Sánchez, Flor I.

Subjects
Life sciences
Abstract

If we want to understand microbial diversity and find new ways to control infectious disease, it is important that we consider the variety of ecological factors that microorganisms normally encounter and how this influences their evolution. Our understanding of interactions between abiotic (e.g. antibiotics) and biotic (e.g. parasites) conditions, and how they affect microbial adaptation remains limited. Specifically, the role of viruses that infect bacteria (phages) in the evolution of antibiotic resistance is an area of growing interest. Not only because viral parasites are important in bacterial ecology and evolution, but also because they have the potential to be used therapeutically. In this thesis I develop and test hypotheses relating to bacterial and viral adaptation in ecologically complex systems. In chapter 1 I give a general introduction to the thesis. In chapter 2, I investigated the role of antibiotic resistance alleles in bacterial responses to parasitic viruses (phages). I show that although some antibiotic resistance alleles can impede the evolution of resistance to phages via growth costs, the overall effect of resistance alleles is relatively weak, as compared to the strong effect of a mutator allele. In chapter 3 I investigated the counteracting effects of antibiotics on bacterial adaptation, specifically, the alteration of mutation supply rates via changes in bacterial population size or bacterial mutation rates. I present evidence that positive mutagenic effects are relatively weak, as compared to the strong negative effects of antibiotics in reducing population size. In chapter 4 I investigated phage host shifting across a range of different bacterial hosts. I used experimental evolution to evolve phage in the presence of novel bacterial host strains. I provide evidence that evolution can result in host shifts, but also in a variety of changes in virulence towards other hosts. In chapter 5 I outline some of the broad themes that emerge from these research projects and point out some of the potential areas for future work.

Published
2018

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