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How to Beat Diffusion: Explorations of Energetics and Spatial Relationships in Microbial Ecosystems


Chadwick, Grayson Lee (2021) How to Beat Diffusion: Explorations of Energetics and Spatial Relationships in Microbial Ecosystems. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/svrp-rb07.


This thesis investigates four microbial systems, with a particular focus for how spatial considerations shape the behavior and evolution of microorganisms. After a general introduction in Chapter 1, Chapter 2 presents the results of experiments demonstrating how cellular activity varies through space within an anode-reducing biofilm. Chapter 3 presents a comprehensive comparative genomic analysis of all known marine anaerobic methanotrophic archaea, supporting the notion that these organisms share many energetic similarities with the anode reducing organisms in Chapter 2. These are interpreted as specific adaptations to life in highly structured microbial communities. Chapter 4 describes the enrichment and characterization of a new member of the purple sulfur bacteria, and the adaptations that may improve substrate acquisition beyond the normal limitations of diffusion. Chapter 5 describes the convergent evolution of novel Complex I gene clusters that have incorporated new proton pumping subunits, and the modifications made to the protein structure to facilitate the incorporation of these new subunits into the quaternary structure of the complex.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Methanotrophy; Microbial ecology; Evolution; Bioenergetics; Environmental microbiology
Degree Grantor:California Institute of Technology
Division:Geological and Planetary Sciences
Major Option:Geobiology
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Orphan, Victoria J.
Thesis Committee:
  • Fischer, Woodward W. (chair)
  • Newman, Dianne K.
  • Leadbetter, Jared R.
  • Orphan, Victoria J.
Defense Date:9 June 2020
Non-Caltech Author Email:graysemail (AT)
Record Number:CaltechTHESIS:07182020-211405749
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 2. adapted for Chapter 5.
Chadwick, Grayson Lee0000-0003-0700-9350
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13842
Deposited By: Grayson Chadwick
Deposited On:24 Jul 2020 15:45
Last Modified:27 Oct 2021 21:46

Thesis Files

PDF (Complete Thesis) - Final Version
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[img] Archive (ZIP) (Supplemental Videos Chapter 4) - Supplemental Material
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