RESOLVING VIRAL AND METABOLIC PROXIES WITHIN MODERN MICROBIALITES

Modern microbialites are benthic organosedimentary structures that provide an analog to Earth's ancient ecosystems. Despite their importance, microbialites and microbial mats are often understudied, especially when trying to understand their formation process, known as lithification. Microbial-viral-mineral interactions may provide catalysts for lithification. This dissertation provided methods that apply to modern microbialites and microbial ecosystems generally. Chapter 2 detailed methods to enumerate viruses and microbes directly via epifluorescence microscopy (EFM) and flow cytometry (FCM). Chapter 3 provides a robust database, NFixDB, for nitrogen fixation enzymes which is critical to all life on Earth. Finally, chapter 4 resolved metabolites and lipids within modern microbialites across the globe. The methodology in Chapter 2 allowed for the direct measurements of viruses (as viral-like particles) within the Great Salt Lake (GSL), which equated to a mass of all the viruses in the GSL to be roughly 2.2 kg or the weight of a standard red brick. From Chapter 4, I resolved the conundrum of nitrogenase related databases by creating the first whole-genome resolved a comprehensive collection of nitrogenases, alternative nitrogenases, pseudo-nitrogenases, and ribosomal subunits found within nitrogen-fixers (i.e., diazotrophs). Finally, a metabolomic and lipidomic study of seven microbialites across the globe were analyzed. Findings revealed carbohydrates, fatty acids, polar lipids, and glycerolipids are the main contributing factors when distinguishing between freshwater and hypersaline environments. Distinct nutrient patterns, organism niches, and stress responses were identified, providing more insight into the microbial interactions that produce microbialites. Altogether, these findings demonstrate the importance of understanding microbialite lithification, especially when identifying factors that may affect larger climates and the entirety of Earth's ecosystems.