Zachary D. Blount

Zachary D. Blount
Michigan State University | MSU · Department of Microbiology and Molecular Genetics

PhD in Microbiology

About

30
Publications
25,765
Reads
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1,755
Citations
Introduction
I am collaborating with Richard Lenski in an ongoing study of a long-term experimental population of E. coli in which a novel trait, aerobic citrate utilization (Cit+), evolved after 31,000 generations of laboratory evolution. My current research projects are aimed at using this population as a model system with which to study speciation, novel trait evolution, the ecological consequences of novel traits, the consequences of analogous versions of innovations, and much more.
Additional affiliations
July 2018 - present
Kenyon College
Position
  • Professor (Assistant)
May 2011 - present
Michigan State University, BEACON Center for the Study of Evolution in Action
Position
  • PostDoc Position
Description
  • Research aimed principally at examining speciation consequent to the evolution of a novel metabolic capacity in E. coli. Job also involves mentoring undergraduate and graduate students.
September 2004 - December 2004
Michigan State University
Position
  • Research Assistant
Description
  • Advanced Microbiology Lab, Fall Semester 2004. I oversaw student work and graded assignments and tests.
Education
August 2003 - May 2011
Michigan State University
Field of study
  • Microbiology and Molecular Genetics
August 2000 - August 2003
University of Cincinnati
Field of study
  • Biological Sciences
September 1995 - June 1999
Georgia Institute of Technology
Field of study
  • Applied Biology

Publications

Publications (30)
Article
Full-text available
The role of historical contingency in evolution has been much debated, but rarely tested. Twelve initially identical populations of Escherichia coli were founded in 1988 to investigate this issue. They have since evolved in a glucose-limited medium that also contains citrate, which E. coli cannot use as a carbon source under oxic conditions. No pop...
Article
Full-text available
Evolutionary novelties have been important in the history of life, but their origins are usually difficult to examine in detail. We previously described the evolution of a novel trait, aerobic citrate utilization (Cit(+)), in an experimental population of Escherichia coli. Here we analyse genome sequences to investigate the history and genetic basi...
Article
Historical processes display some degree of “contingency,” meaning their outcomes are sensitive to seemingly inconsequential events that can fundamentally change the future. Contingency is what makes historical outcomes unpredictable. Unlike many other natural phenomena, evolution is a historical process. Evolutionary change is often driven by the...
Preprint
Full-text available
Evolutionary innovations allow populations to colonize new, previously inaccessible ecological niches. We previously reported that aerobic growth on citrate (Cit +) evolved in a population of Escherichia coli during adaptation to a minimal glucose medium containing citrate (DM25). Cit + can grow in citrate-only medium (DM0), which is a novel enviro...
Chapter
Full-text available
Evolution innovates by repurposing existing genetic elements to produce new functions. However, the range of new functions and traits this evolutionary tinkering can produce is limited to those that are supported and enabled by the rest of the genome. The full complement of genes in a genome required for a novel trait to manifest constitutes the tr...
Article
Full-text available
Evolutionary innovations allow populations to colonize new ecological niches. We previously reported that aerobic growth on citrate (Cit⁺) evolved in an Escherichia coli population during adaptation to a minimal glucose medium containing citrate (DM25). Cit⁺ variants can also grow in citrate-only medium (DM0), a novel environment for E. coli. To st...
Article
Full-text available
Evolutionary innovations allow populations to colonize new ecological niches. We previously reported that aerobic growth on citrate (Cit⁺) evolved in an Escherichia coli population during adaptation to a minimal glucose medium containing citrate (DM25). Cit⁺ variants can also grow in citrate-only medium (DM0), a novel environment for E. coli. To st...
Article
Full-text available
Evolutionary innovations allow populations to colonize new ecological niches. We previously reported that aerobic growth on citrate (Cit⁺) evolved in an Escherichia coli population during adaptation to a minimal glucose medium containing citrate (DM25). Cit⁺ variants can also grow in citrate-only medium (DM0), a novel environment for E. coli. To st...
Article
A fitness landscape is a map between the genotype and its reproductive success in a given environment. The topography of fitness landscapes largely governs adaptive dynamics, constraining evolutionary trajectories and the predictability of evolution. Theory suggests that this topography can be deformed by mutations that produce substantial changes...
Preprint
Full-text available
A fitness landscape is a map between the genotype and its reproductive success in a given environment. The topography of fitness landscapes largely governs adaptive dynamics, constraining evolutionary trajectories and the predictability of evolution. Theory suggests that this topography can be "deformed" by mutations that produce substantial change...
Article
Full-text available
Article
Full-text available
Biological evolution is a fundamentally historical phenomenon in which intertwined stochastic and deterministic processes shape lineages with long, continuous histories that exist in a changing world that has a history of its own. The degree to which these characteristics render evolution historically contingent, and evolutionary outcomes thereby u...
Article
Full-text available
Many populations live in environments subject to frequent biotic and abiotic changes. Nonetheless, it is interesting to ask whether an evolving population's mean fitness can increase indefinitely, and potentially without any limit, even in a constant environment. A recent study showed that fitness trajectories of Escherichia coli populations over 5...
Data
E. coli strains and plasmids used in this study. DOI: http://dx.doi.org/10.7554/eLife.09696.015
Data
Mutations used to track clade dynamics in the LTEE.DOI: http://dx.doi.org/10.7554/eLife.09696.005
Data
Details for all gltA alleles in this study.DOI: http://dx.doi.org/10.7554/eLife.09696.004
Article
Full-text available
In a long-term evolution experiment with Escherichia coli, bacteria in one of twelve populations evolved the ability to consume citrate, a previously unexploited resource in a glucose-limited medium. This innovation led to the frequency-dependent coexistence of citrate-consuming (Cit+) and non-consuming (Cit–) ecotypes, with Cit– bacteria persistin...
Article
Full-text available
Evolution of a novel function can greatly alter the effects of an organism on its environment. These environmental changes can, in turn, affect the further evolution of that organism and any coexisting organisms. We examine these effects and feedbacks following evolution of a novel function in the long-term evolution experiment (LTEE) with Escheric...
Article
Full-text available
In a long-term evolution experiment with Escherichia coli, bacteria in one of twelve populations evolved the ability to consume citrate, a previously unexploited resource in a glucose-limited medium. This innovation led to the frequency-dependent coexistence of citrate-consuming (Cit+) and non-consuming (Cit-) ecotypes, with Cit-bacteria persisting...
Thesis
Full-text available
The importance of historical contingency in evolution has been extensively debated over the last few decades, but direct empirical tests have been rare. Twelve initially identical populations of E. coli were founded in 1988 to investigate this issue. They have since evolved for more than 50,000 generations in a glucose-limited medium that also cont...
Article
Analyses of complete genomes indicate that insertion sequences (ISs) are abundant and widespread in hyperthermophilic archaea, but few experimental studies have measured their activities in these hosts. As a way to investigate the impact of ISs on Sulfolo-bus genomes, we identified seven transpositionally active ISs in a widely distributed Sulfolob...
Article
Analyses of complete genomes indicate that insertion sequences (ISs) are abundant and widespread in hyperthermophilic archaea, but few experimental studies have measured their activities in these hosts. As a way to investigate the impact of ISs on Sulfolobus genomes, we identified seven transpositionally active ISs in a widely distributed Sulfolobu...
Book
Full-text available
2 OVERVIEW Biol 552 has a challenging goal, which is to give students practical experience and training in the fundamentals of microbiology. Practical experience is especially important because microbiology is one of the most experimental branches of biology. With the proper techniques, huge numbers of individuals of a microbial species can be prod...
Article
Full-text available
Thesis (M.S.)--University of Cincinnati, 2003. Includes bibliographical references. Includes abstract.

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Projects

Projects (5)
Archived project
Soon after Cit+ rose to dominance in the Ara-3 LTEE population around 33,000 generations, the Cit- lineage that ended up coexisting in the population for 10,000 generations evolved to cross feed on C4-dicarboxylates released into the medium by Cit+ during its growth on citrate, as shown by Turner et al 2015. This new capacity allowed Cit- to straddle at least two niches: glucose and C4-dicarboxylates. By 34,000 generations, the value of the occupation of this latter niche was obvious - a Cit- clone able to access the cross feeding niche could maintain an equilibrium population in co-culture with a Cit+ clone that was 10-fold higher than one that could not. However, by 43,000 generations, the bulk of the value of access to this niche was gone. Data from the project looking at Cit+ speciation shows that Cit+ evolved high competitiveness for C4-dicarboxylates, which, together with this finding suggests that Cit+ invaded the C4-dicarboxylate niche and pushed Cit- out. When did this happen? Was the invasion sudden, or gradual? Did Cit- persist by increased specialization for glucose? Is there more to the story? To find out, we, with Brooke Sommerfeld on point, are looking at how the ecological relationships between Cit+ and Cit- with regard to the C4-dicarboxylate niche changed over time, and what adaptations this dance entailed in each ecotypes.
Project
The evolutionary consequences of novel traits may be impacted not simply by their occurrence, but by the manner by which they are actualized. During the course of replay experiments to examine the role of historical contingency in the evolution of aerobic citrate growth (Cit+) after 31,000 generations in a long-term experimental population of E. coli, I isolated a number of citrate variants with different actualizing mutations to the one that caused the phenotypic switch actually observed. How do the details of how a novel trait is actualized impact subsequent evolution of that trait? To examine this question, I am constructing Cit+ variants with the actualizing mutations that could have occurred, and will evolve them under LTEE conditions. I will then examine differences in evolutionary trajectory, ecological consequences, and genetic changes.
Project
Novel traits normally evolve by co-option or modification of pre-existing components, building the new upon the old. E. coli normally cannot grow aerobically (Cit+) on citrate. A Cit+ variant evolved in a population of E. coli more than 31,000 generations into a long-term evolution experiment. We demonstrated that this trait's evolution in the population was contingent upon at least two prior mutations that had accumulated during the course of the population's history. The trait itself was actualized by an amplification mutation that placed a normally silent citrate transporter under the control of an aerobic promoter. We are currently seeking to determine what pre-existing genes in the E. coli genome were required for manifestation of the Cit+ trait beyond those immediately involved in the phenotypic switch. These genes constitute what we consider the deep genetic context required for Cit+ evolution. We expect this work will shed light on citrate metabolism in the E. coli, as well as on how novel traits evolve.