Exploring Versatility of Energy Metabolism and Dynamics of Anabolism and Growth in Anaerobic Methanotrophic Consortia

Citation

Guo, Yongzhao (2025) Exploring Versatility of Energy Metabolism and Dynamics of Anabolism and Growth in Anaerobic Methanotrophic Consortia. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/fz82-xt77. https://resolver.caltech.edu/CaltechTHESIS:06022025-214449948

Abstract

Two main questions are asked in this thesis, how environmental microorganisms respond and persist in an energy-limiting condition, and how we can investigate and disentangle the dynamics of these microbes’ activity and growth at a high spatiotemporal resolution. To the end, this thesis focuses on a symbiosis of methane oxidizing archaea (ANME) and sulfate reducing bacteria (SRB), who mediate the anaerobic oxidation of methane (AOM), an important process in the global methane cycle. For the former question, Chapter 2 first found that carbon monoxide (CO) was able to serve as an alternative electron donor for ANME-SRB, and notably CO can even reverse the direction of AOM in ANME archaea to produce methane by the reduction of CO₂. Chapter 3 then explored and verified from the other side the potential role of pyrite (nano)particles in supporting AOM via a predicted reaction at the pyrite-water interface to generate sulfate and iron oxides as electron sinks. For the latter question, Chapter 4 took advantage of stable isotopic probing combined with the high sensitivity and spatial resolution of nanometer-scale secondary ion mass spectrometry (nanoSIMS) approach, and proposed a pipeline of multi-isotope imaging to record and in situ read out the single cell activity in the past. Chapter 5 as an in progress work attempts to disentangle the native division process in the yet uncultured ANME archaea by means of serial block face electron microscopy (SBEM) and deep learning imaging analysis. Taken together, this work provides more evidence of the versatile energy metabolism for ANME-SRB symbiosis and at the same time offers solutions to capturing the dynamics of activity and growth in natural microorganisms for the field of environmental microbiology.

Thesis Files