DOCSLIB.ORG

Genetic Robustness and Adaptability of Viruses

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Genetic Robustness and Adaptability of Viruses Genetic Robustness and Adaptability of Viruses Phage can develop differing sensitivities to mutations, strongly affecting their adaptive potential in varied environments Robert C. McBride and Paul E. Turner iodiversity reflects billions of years of brittleness are terms used for measuring and adaptation through natural selection, describing the relative accuracy of this geno- whereby environments help to deter- type-to-phenotype translation. In particular, ge- B mine which genetic variants in a pop- netic robustness is the constancy of a phenotype ulation persist. This process leads in the face of changes in the underlying geno- some individuals in a population to possess type. If a mutation changes a phenotype, we traits that prove beneficial in a particular niche consider the gene or, more broadly, the genome, and can help to distinguish them from other to be relatively nonrobust, or brittle, against organisms residing there or elsewhere. Although mutational input. However, if a genome evolution is defined as the change in genetic changes but phenotype remains unaffected, the makeup of a population through time, natural genome is considered genetically robust. Be- selection acts on phenotypes. That is, natural cause other types of robustness are of interest, selection leads indirectly to changes in gene fre- especially environmental robustness that de- quencies by acting on the phenotypes that genes scribes whether a phenotype persists when an produce. environment changes, it is crucial when examin- Thus, the translation of phenotype from geno- ing robustness to define the specific phenotype type is crucial to evolution. Robustness and and perturbation being measured and discussed. Many phenotypic traits could be used to study robustness. From an evolutionary Summary perspective, however, traits that constitute • fitness, the relative ability to survive and Robustness and brittleness describe the relative reproduce, are of greatest interest. accuracy of genotype-to-phenotype translation, which is crucial to evolution. Comprehensive measurement of fitness is prohibitively difficult for many organisms. • Examining the balance between robustness and evolvability, the capacity to adapt, can help in Fortunately, because so many microbes determining whether natural selection shapes grow asexually, microbiologists can readily evolution itself. measure population-level traits for a partic- Robert C. McBride • Despite some perceived obstacles, microbial ular microbial genotype. Thus, two proxies is a Postdoctoral studies, particularly those involving phage, are for genotype fitness are the reproductive Associate in Ecol- helping to fill gaps in our knowledge of robust- growth rate and the numerical size of a ogy and Evolution- ness. population grown from that genotype. ary Biology and • Because pathogenic viruses may adapt to treat- However, typically it is more desirable to Paul E. Turner is ments by developing greater resistance and measure fitness of a microbial genotype us- Associate Professor greater potential to withstand future therapies, ing an experimental assay where two strains of Ecology and Evo- caution is warranted when considering muta- genic therapies. are placed in the same environment and lutionary Biology at their fitness is gauged relative to one an- Yale University, other or to some baseline, such as a single New Haven, Conn. Volume 3, Number 9, 2008 / Microbe Y 409 common-competitor genotype. In this way, re- genetic robustness, i.e., phenotypic constancy searchers can efficiently and accurately measure despite mutational input. Were a population to relative fitness of microbial genotypes, and become optimally adapted to its habitat, any quantify genotype robustness in the face of mutation would be either neutral or deleterious. change. This scenario should then lead to strong selec- tion for genetic robustness to evolve, protecting the phenotype against mutations. In a related Robustness Provides Insights into the sense, because spontaneous mutations are be- Relationship between Phenotype, lieved typically to be deleterious, selection fa- Genotype voring evolution of robustness should be espe- Improved understanding of the fundamental re- cially strong if mutation rates are elevated, even lationship between phenotype and genotype when populations are away from equilibrium. provides a clear reason for studying the evolu- Some convincing data on evolution of robust- tion of robustness. On the one hand, constancy ness stem from studies looking at virtual organ- in the face of environmental and mutational isms—namely, self-replicating computer pro- changes provides obvious benefits to an organ- grams that change randomly and thus “evolve.” ism during replication. Robustness buffers or- According to one such study, elevated mutation ganisms against such perturbations, affording rates can cause robust genotypes to be selec- constancy in terms of cellular function, develop- tively favored over their brittle counterparts, ment, and offspring production. That is, robust- even though robustness against mutations went ness provides reliability in the very currencies by hand-in-hand with lower reproductive fitness. which natural selection judges phenotypes. Thus, the fittest gave way to the “flattest,” with However, rigidity in the face of change may selection favoring those variants having the pose problems. For example, if organisms are greatest phenotypic constancy and residing on steadfast under environmental change, how can flat regions of the fitness landscape (Fig. 1). they possibly adapt to new conditions? Because Other studies successfully examine robustness natural selection acts on phenotypic variation, by following changes in proteins in vitro. robustness that buffers this variation could im- Microbial populations provide another trac- pede evolution. table choice for examining robustness because These conflicting necessities force organisms of their rapid generation times and large popu- to strike a balance between withstanding some lation sizes. However, microorganisms still re- changes and maintaining an ability to adapt to quire extensive time before selection begins to new circumstances. This compromise is the bal- favor variants that evolve increased robustness. ance between robustness and evolvability, the The limiting factor is time needed to achieve an capacity to adapt. By examining this balancing adaptive optimum. For example, fitness in pop- act, we may learn whether evolvability can itself ulations of Escherichia coli continues to change, evolve. Thus, we can explore the intriguing— even after 40,000 generations (20 years), ac- and contentious—idea that natural selection cording to Richard Lenski of Michigan State shapes evolution itself. University in East Lansing and his colleagues. This result suggests a difficulty for researchers in relying on laboratory populations to examine How Is Robustness Studied? selective pressures favoring evolution of robust- Despite a longstanding interest in robustness ness. and extensive mathematical modeling, biolo- Although some theory suggests that evolu- gists have generated few data on this subject tionary changes in robustness might be difficult because studying robustness presents many to observe in laboratory populations of mi- challenges. One hurdle is to identify organisms crobes, these systems remain the most attractive that vary in robustness. Traits favoring robust- means for conducting experiments to examine ness are not expected to be strongly selected evolution. Despite some perceived obstacles, mi- until a biological population reaches evolution- crobial studies are helping to fill gaps in our ary equilibrium—mutation-selection balance— knowledge of robustness. After all, microbes are in a constant environment. immensely successful from an evolutionary This prerequisite should be especially true for standpoint; they thrive in all habitats that sup- 410 Y Microbe / Volume 3, Number 9, 2008 port life, and they are the most plentiful FIGURE 1 denizens of Earth. Over billions of years, microbes have experienced ex- tensive selection to shape robustness. RNA viruses seem particularly ap- propriate for examining genetic robust- ness, a view that mathematical theory supports. According to digital organism experiments, elevated mutation rates are a key prerequisite for populations to adapt by altering their genetic (mu- tational) robustness. Therefore, success may come from studying genetic ro- bustness in biological systems with ele- vated mutation rates, making RNA vi- ruses even better candidates because their mutation rates generally exceed those of other organisms, including DNA viruses, by at least one order of magni- tude. By focusing on RNA systems, it is possible to study the evolution of ro- bustness even when populations are not at an evolutionary equilibrium or are not subject to artificially elevated muta- tion rates through mutagenesis. Can Robustness Evolve? Several independent studies show that robustness can increase or decrease, de- Schematic where brittle and robust organisms are defined by their fitness response to pending on the particulars of the selec- mutational change, using the metaphor of fitness landscapes. Fitness is vertical height tive environment. For example, we used on the landscape. Mutation causes genotypes to move away from their original position a single genotype of the lytic RNA bac- on the horizontal axis. After mutation, brittle individuals experience large changes in fitness as they are “pushed off” the narrow fitness peak. In contrast,
Load more

Recommended publications
  • Michael Behe Makes the Argument That
    Opening the Black Box Throughout “Darwin’s Black Box”, Michael Behe makes the argument that Darwinian evolution can’t be used as a universal explanation for all of life, because it can’t account for irreducibly complex organisms. However, Behe also neglects to acknowledge any existing research that suggests otherwise. A study conducted at Michigan State University by scientist Richard Lenski has shown that there could be a scientific explanation for these seemingly irreducibly complex organism, and that Behe shouldn’t be so quick to point to a supernatural solution, or to call it quits so soon when his mousetrap breaks. While Behe may think he has all the answers, contrary research has shown there are other answers worth consideration. Behe begins his argument by introducing the idea of organisms that are irreducibly complex, otherwise defined as a “single system composed of several well-matched, interacting parts that contribute to the basic function of the system, wherein the removal of any one of the parts causes the system to effectively cease functioning” (Darwin’s Black Box, 39). In order to demonstrate this principle, Behe raises the example of a mousetrap. He argues that if you remove one part of a mousetrap, it will cease to function, and because of this, all of the parts must have evolved simultaneously in order for a mousetrap to exist, therefor rendering it irreducibly complex. However, is any of this really true? Besides the holes in Behe’s mousetrap argument, there also lies the fact that mousetraps are not living creatures and therefore are incapable of evolution.
    [Show full text]
  • Chapter 6.Qxp
    Testing Darwin Digital organisms that breed thousands of times faster than common bacteria are beginning to shed light on some of the biggest unanswered questions of evolution BY CARL ZIMMER F YOU WANT TO FIND ALIEN LIFE-FORMS, does this. Metabolism? Maybe not quite yet, but Ihold off on booking that trip to the moons of getting pretty close.” Saturn. You may only need to catch a plane to East Lansing, Michigan. One thing the digital organisms do particularly well is evolve. “Avida is not a simulation of evolu- The aliens of East Lansing are not made of car- tion; it is an instance of it,” Pennock says. “All the bon and water. They have no DNA. Billions of them core parts of the Darwinian process are there. These are quietly colonizing a cluster of 200 computers in things replicate, they mutate, they are competing the basement of the Plant and Soil Sciences building with one another. The very process of natural selec- at Michigan State University. To peer into their tion is happening there. If that’s central to the defi- world, however, you have to walk a few blocks west nition of life, then these things count.” on Wilson Road to the engineering department and visit the Digital Evolution Laboratory. Here you’ll It may seem strange to talk about a chunk of find a crew of computer scientists, biologists, and computer code in the same way you talk about a even a philosopher or two gazing at computer mon- cherry tree or a dolphin. But the more biologists itors, watching the evolution of bizarre new life- think about life, the more compelling the equation forms.
    [Show full text]
  • Life's Conservation Law: Why Darwinian
    William A. Dembski and Robert J. Marks II, "Life's Conservation Law: Why Darwinian Evolution Cannot Create Biological Information" in Bruce Gordon and William Dembski, editors, The Nature of Nature (Wilmington, Del.: ISI Books, 2011) pp.360-399 E F E IS an irn:volcaIJ!e selection and exclusion. as when you marry one woman you up all the so when you take one course of action you up all the other courses."4 Intelligence creates information. Bur is the causal power of Darwin's main claim to fame is that he is supposed to have a that could create informa- tion without the need intelligence. Interestingly, he to this mechanism as "natural selection." Sel.e~tion, as understood before had been an activity confined to intelligent agents. Darwll1 s great coup was to the power to nature-hence "natural selection." as conceived Darwin and his acts without is non-teleo- and therefore unintelligent. As genetlClst Coyne puts it in opposing intdlige:nt "If we're to defend we must defend it as a science: a in which the of life results from the action natural selection and on random mutations."5 But do and Darwinists insist that to count as must be non-teleological?6 did that rule come from? The of with the sciences is itselfa well-established science-it's called engineering. conceived, to the engi- ne.:::nng SCIences. 1. THE CREATION OF INFORMATION But to return to the at does nature really possess the power to select and th,>rph" create To answer this we to turn to relation between po~,sit)ilil:ies to create inlonnal:1011.
    [Show full text]
  • The Landscape of Innovation in Bacteria, Battleships, and Beyond Downloaded by Guest on October 1, 2021 Thus, Fig
    SPECIAL FEATURE: PERSPECTIVE The landscape of innovation in bacteria, battleships, and beyond SPECIAL FEATURE: PERSPECTIVE Terence C. Burnhama,b,1 and Michael Travisanoc,d,1,2 Edited by Simon A. Levin, Princeton University, Princeton, NJ, and approved November 18, 2020 (received for review August 12, 2020) We draw lessons from microbial experimental evolution and naval warfare to improve the understanding of innovation in financial markets. Major financial innovations often arise without explicit societal planning because novel approaches can be favored by markets, in a manner strikingly parallel to natural selection. We utilize the concept of an adaptive landscape to characterize environments that increase the speed and magnitude of innovation. We apply this adaptive landscape framework to innovation in portfolio management. We create a general taxonomy for understanding and nurturing innovation. adaptation | experimental evolution | finance | innovation What environmental characteristics favor innovation? relationship between design and performance. Con- We begin with an examination of innovation evident in sequently, both battleship and bacterial innovation naval warfare, primarily the design and function of can be represented in a similar adaptive landscape. battleships. Improvements in battleships suggest that We draw general lessons regarding approaches to fierce competition fosters innovation. innovation, aided by the adaptive landscape repre- While the battleship heuristic appears straightfor- sentation. The goal is to understand innovation in ward, the study of any historical set of innovations has finance and other domains. From this perspective, we the challenge of disentangling causation from corre- analyze one area of finance: the management of lation. Without a time machine, we cannot be sure of investment portfolios.
    [Show full text]
  • Experiments in Digital Evolution Christoph Adami∗ Claus O
    Experiments in Digital Evolution Christoph Adami∗ Claus O. Wilke (Editors’ Introduction to the Digital Life Laboratory 136-93 Special Issue) California Institute of Technology Pasadena, CA 91125 {adami,wilke}@caltech.edu Whether or not the field of artificial life has succeeded in doing what its name sug- gests, namely synthesizing life from non-living components, is a matter of contention. Clearly, this journal covers a broad range of topics related to the synthesis and sim- ulation of living systems, but only a few articles go so far as to unabashedly study wholly artificial forms of life. The field of digital evolution is an exception: Artificial life forms, in the form of self-replicating computer code inhabiting specially prepared areas of a standard computer, have been used to learn about fundamental aspects of the evolutionary process since Tom Ray introduced us to them [23]. In this issue, we present experiments using digital organisms of the Avida variety (that is, implemented with the Avida software described in this issue [20]), but there are a number of other implementations of digital evolution that have been used for experimental evolution (see, e.g., [31, 32, 22, 5]). Whether or not these digitals are truly alive is ultimately of no concern to us as researchers: We use them because we are interested in complicated and vexing questions of evolutionary biology, and digitals offer us the possibility to attack them. Digital evolution is currently undergoing a boom phase, and public perception of this discipline is steadily increasing [21]. This boom can be traced back in part to a maturation of the Avida software used in the majority of digital evolution experiments, in part to a perceived need for rigor in evolution experiments [7], and in part to the adoption of digitals as experimental organisms alongside bacteria and viruses by a growing number of microbiologists (see, e.g., [16]).
    [Show full text]
  • Week 4: Evolution: Genetics, Epigenetics and the Environment May 8, 2018
    1 Week 4: Evolution: Genetics, Epigenetics and the Environment May 8, 2018 “Imagine landing a time machine 3 billion years ago in shallow costal waters. The first thing you notice is that the sky is not blue, but a dull hazy red, a touch reminiscent of Mars. The quiet seas reflect in shades of red. It’s pleasantly warm in this haze, if too misty to see the sun clearly. On land not much catches the eye. The rocks are bare, with damp patches of discoloration here and there, bacteria clinging precariously to their extreme terrestrial outpost. There’s no grass or vegetation of any sort. But marching through the shallow waters are scores of strange domes of greenish rock. Apparently the work of life, the tallest are a metre or so high. A few familiar rare structures are still found in the most remote and inaccessible bays on earth today: stromatolites. Nothing else stirs the waters. There’s no fish here, no seaweed, no scuttling crabs, no waving anemones. Take off your oxygen mask, and you’ll soon understand why: you’ll suffocate in minutes. There’s barely any oxygen, even close to the stromatolites. Yet their blue- green bacteria, cyanobacteria, are already beginning to lace the air with traces of that hazardous gas. In a billion years, their emissions will finally turn our planet vivid green and blue. And only then will we recognize this bare place as home.” From Lane N. (2009) Life Ascending: The Ten Great Inventions of Evolution, W.W. Norton & Company, New York London, Page 263*** 2 Introduction One of my favorite BBC programs is based on the veterinarian James Herriot’s book series, ‘All Creatures Great & Small.’ The story chronicles the adventures of Herriot and his colleagues in a rural, mostly large animal veterinarian practice in York in the 1930’s through to the 1950’s.
    [Show full text]
  • Microbial Evolution in Action Richard E. Lenski
    Microbial evolution in action Richard E. Lenski In his introduction Most of us first encountered evolution as child- more fit than its ancestor under one set of conditions does to this issue on Gren, when we saw the fossil remains of dinosaurs not imply that it would be more fit elsewhere. microbial evolution, and other extinct organisms in museums. As Some years ago, I began a long-term experiment in Richard Lenski biologists, we also see the grand sweep of evolution which 12 populations of Escherichia coli began from the recorded in the genomes of living organisms and, as micro- same ancestral strain and have evolved in identical, describes his own biologists, we see on-going evolution in the emergence of defined environments for more than 20,000 bacterial research into E. coli microbes resistant to antimicrobial agents. Until recently, generations (see Fig. 1). My two main objectives were to populations and few viewed evolution as an experimental science. This examine the reproducibility of evolution and to explore puts the other is now changing as microbes are increasingly used in the coupling between phenotypic and genomic changes. articles into context. designed experiments to test various hypotheses about In short, all the populations have become much more fit evolutionary dynamics, patterns and mechanisms. in the glucose-limited environment in which they For decades, some microbes served as model organisms evolved; at the end of 20,000 generations they grow about in genetics and molecular biology. The same advantages – 75 % faster than the ancestor when they compete head-to- ease of culture, rapid generations and large populations – head for glucose.
    [Show full text]
  • Evolutionary Dynamics of Speciation and Extinction
    Scholars' Mine Doctoral Dissertations Student Theses and Dissertations Fall 2015 Evolutionary dynamics of speciation and extinction Dawn Michelle King Follow this and additional works at: https://scholarsmine.mst.edu/doctoral_dissertations Part of the Biophysics Commons Department: Physics Recommended Citation King, Dawn Michelle, "Evolutionary dynamics of speciation and extinction" (2015). Doctoral Dissertations. 2464. https://scholarsmine.mst.edu/doctoral_dissertations/2464 This thesis is brought to you by Scholars' Mine, a service of the Missouri S&T Library and Learning Resources. This work is protected by U. S. Copyright Law. Unauthorized use including reproduction for redistribution requires the permission of the copyright holder. For more information, please contact [email protected]. 1 EVOLUTIONARY DYNAMICS OF SPECIATION AND EXTINCTION by DAWN MICHELLE KING A DISSERTATION Presented to the Faculty of the Graduate Faculty of the MISSOURI UNIVERSITY OF SCIENCE AND TECHNOLOGY and UNIVERSITY OF MISSOURI AT SAINT LOUIS In Partial Fulfillment of the Requirements for the Degree DOCTOR OF PHILOSOPHY in PHYSICS 2015 Approved by: Sonya Bahar, Advisor Ricardo Flores Nevena Marić Paul Parris Thomas Vojta 1 iii ABSTRACT Presented here is an interdisciplinary study that draws connections between the fields of physics, mathematics, and evolutionary biology. Importantly, as we move through the Anthropocene Epoch, where human-driven climate change threatens biodiversity, understanding how an evolving population responds to extinction stress could be key to saving endangered ecosystems. With a neutral, agent-based model that incorporates the main principles of Darwinian evolution, such as heritability, variability, and competition, the dynamics of speciation and extinction is investigated. The simulated organisms evolve according to the reaction-diffusion rules of the 2D directed percolation universality class.
    [Show full text]
  • Joris Van Rossum on Sexual Reproduction As a New Critique of the �Eory of Natural Selection
    Joris van Rossum On Sexual Reproduction as a New Critique of the �eory of Natural Selection On Sexual Reproduction as a New Critique of the Theory of Natural Selection Vrije Universiteit On Sexual Reproduction as a New Critique of the eory of Natural Selection Academisch Proefschrift ter verkrijging van de graad Doctor aan de Vrije Universiteit Amsterdam, op gezag van de rector magni�cus prof. dr. L.M. Bouter, in het openbaar te verdedigen ten overstaan van de promotiecommissie van de Faculteit der Wijsbegeerte op dinsdag 11 december 2012 om 9.45 uur in de aula van de universiteit, De Boelelaan 1105 door Joris Paul van Rossum geboren te Nijmegen Promotoren Prof. dr. R. van Woudenberg Prof. dr. R.W.J. Meester Copyright © 2012 by Joris van Rossum All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmi�ed, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without prior permission in writing of the author. Reprinted with minor corrections, 2013 Designed by Hans Stol Cover image based on a design by Paul Rand Printed in �e Netherlands by Printforce ISBN 978-90-9027200-9 NUR 738 Amsterdam 2012 Table of Contents Preface 7 Introduction 11 I Background 25 II �e Inability of the �eory of Natural Selection to Explain Sexual Reproduction 45 III An Analysis of Darwinian A�empts to Explain Sexual Reproduction and ‘�e Queen of Evolutionary Problems’ 111 IV Discussion 133 Summary in Dutch 171 References 177 Flower in the crannied wall, I pluck you out of the crannies, I hold you here, root and all, in my hand, Li�le �ower – but if I could understand What you are, root and all, and all in all, I should know what God and man is.
    [Show full text]
  • A Poke in the Eye.Indd
    Answers in Depth, Vol. 3, (2008), pp. 45–47. https://assets.answersingenesis.org/doc/articles/aid/v3/poke-in-eye.pdf A Poke in the Eye? Lenski and the adaptive acrobatics of E. coli Georgia Purdom, Ph.D., Answers in Genesis Keywords creationists, Richard Lenski, information, functional systems, E. coli Jerry Coyne, evolutionary biologist at the University of Chicago, thinks that Richard Lenski’s recently published research on citrate utilization by Escherichia coli1 is just that—“another poke in the eye for anti- evolutionists.”2 He goes on to say, “The thing I like most is it says you can get these complex traits evolving by a combination of unlikely events. That’s just what creationists say can’t happen.”3 I agree that creationists say that cannot happen; however, Lenski’s research does not show that it did! Instead Lenski’s research is another “feather in the cap” for creationists and further demolishes evolutionary ideas that complex traits can arise by random mutations. Lenski’s 20-Year Experiment In 1988 Richard Lenski, an evolutionary biologist at Michigan State University, began culturing 12 identical lines of E. coli. Over 44,000 generations and 20 years later, the experiment continues. The bacteria are grown in medium, which has a small amount of glucose (a primary carbon source for E. coli) and abundant citrate (a carbon source not utilized by E. coli). Every 500 generations, his lab takes samples of the bacteria, which in essence produces a “fossil record” of the different lines. Lenski has observed many changes in the E. coli as they adapt to the culture conditions in his lab.
    [Show full text]
  • Avida-ED Lab Book Summer 2017 Active LENS Workshop Version
    Avida-ED Lab Book Summer 2017 Active LENS Workshop Version Avidians in Action Avida-ED Project Curriculum Development Team Wendy Johnson, Cory Kohn, Amy Lark, Louise Mead, Robert T. Pennock, Jim Smith, Michael Wiser http://avida-ed.msu.edu http://bit.do/avida-ed This material is based in part upon work supported by the National Science Foundation under NSF-IUSE (NSF Grant # 1432563), "Active LENS: Learning Evolution and the Nature of Science using Evolution in Action", Robert T. Pennock, PI, Richard Lenski, Louise Mead, Charles Ofria, James J. Smith, co-PIs. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Preface This is the summer 2017 edition of the Avida-ED Lab Book as prepared for the Michigan State University course IBIO150 – Integrative Biology: From DNA to Populations – and the Avida-ED Active LENS Train-the Trainers Workshops. This edition’s activities have been substantially reworked for greater clarity and biological content depth, pedagogical scaffolding, and student engagement. Though the activities are similar to their past iterations, experienced Avida-ED instructors should refamiliarize themselves with the content. Of particular note, the Lab Book now contains a fourth focal Exercise, which investigates population change due to random processes – genetic drift. Based on feedback from Active LENS faculty development workshop participants, the 2016 edition reversed the order of exercises 2 and 3, and incorporated a change of terminology to help students better understand the factors that lead to changes in an organism’s fitness.
    [Show full text]
  • Fixation and Adaptation in the Lenski E. Coli Long Term Evolution Experiment
    Research Article ISSN: 2574 -1241 DOI: 10.26717/BJSTR.2019.20.003392 Fixation and Adaptation in the Lenski E. coli Long Term Evolution Experiment Alan Kleinman* Department of Medicine, USA *Corresponding author: Alan Kleinman, Department of Medicine, USA ARTICLE INFO Abstract Received: July 18, 2019 may or may not be occurring together in an evolutionary process. In this study, we Published: July 25, 2019 Evolutionary adaptation and fixation are distinct physical processes. These processes Citation: Alan Kleinman. Fixation and demonstrate both mathematically and empirically that fixation is not necessary for Adaptation in the Lenski E. coli Long process,adaptation the (improvement Lenski E. coli inlong fitness) term toevolution occur. And experiment if fixation is is derived required with for a adaptation, numerical Term Evolution Experiment. Biomed solutionit slows theand evolutionary this solution adaptation is used toprocess. analyze The smaller mathematics and larger of a particularcarrying capacityfixation J Sci & Tech Res 20(1)-2019. BJSTR. environments. MS.ID.003392. Keywords: Evolution; Fixation; Adaptation; Mathematical Model Introduction [6] and the particular evolutionary components which cause the experiment to act in its manner. And to address why it takes so understanding of the particular components that make up that Any understanding of an evolutionary process requires the evolutionary process. Darwin wrote about these evolutionary processes in his book, “On the Origin of Species”[1]. From this many generations for each fixation and adaptation step. A model and edited by Richard Lenski where they discuss these issues [7]. for fixation was presented in the following paper BH Good, et al. it should be remembered that the competition will generally be Their model doesn’t directly model the LTEE, however, we will text, we get a particular quote that describes these processes: “For most severe between those forms which are most nearly related to each other in habits, constitution and structure.
    [Show full text]