In partial fulfillment of the requirements for the degree of

Doctor of Philosophy in Biology

in the

School of Biological Sciences

Marcus S. Bray

Will defend his thesis

Iron as an integral constituent of ancient metabolism and biochemistry

Thursday April 25th, 2019

1:00 PM

Engineered Biosystems Building (EBB)

Children’s Healthcare of Atlanta Seminar Room (1005)

Thesis Advisor:

Dr. Jennifer B. Glass

School of Earth and Atmospheric Sciences

Georgia Institute of Technology

Thesis Co-Advisor:

Dr. Loren Dean Williams

School of Chemistry and Biochemistry

Georgia Institute of Technology

Committee members:

Dr. Frank J. Stewart

School of Biological Sciences

Georgia Institute of Technology

Dr. Joel E. Kostka

School of Biological Sciences

Georgia Institute of Technology

Dr. Kostas T. Konstantinidis

School of Civil and Environmental Engineering

Georgia Institute of Technology

Summary

Life on Earth evolved and proliferated for nearly 2 billion years in an environment devoid of molecular oxygen and replete with iron. Currently on Earth, iron has widespread uses in the biochemistry and metabolism of extant organisms. It is therefore likely that this metal filled a larger role at life’s inception and colonization across the planet. In this dissertation, I investigated the roles that iron could have played for early biochemistry and lifeforms. I first studied iron’s ability to substitute for magnesium in life’s old macromolecular machine, the ribosome. I found that under conditions reminiscent of the ancient Earth, iron can mediate ribosomal structure and function in place of magnesium both in vitro and in vivo. I then examined the mechanisms microorganisms use to respire iron, and the how this ancient metabolism interacts with others in the environment. I found that certain iron reducing strategies may me more phylogenetically and structurally diverse than previously realized, and that the competing interest of iron reducing organisms with methanogens in sediments could have constrained early planetary habitability. Collectively, my results deepen our knowledge of not only the past, but present and future of iron in life on this planet.