{"686267":{"#nid":"686267","#data":{"type":"event","title":"PhD Defense by Autumn Peterson","body":[{"value":"\u003Cp\u003EIn partial fulfillment of the requirements for the degree of\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EDoctor of Philosophy in Biology\u003C\/p\u003E\u003Cp\u003EIn the\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAutumn Peterson\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EWill defend her dissertation\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EUsing synthetic biology and experimental evolution to reconstruct major evolutionary innovations\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E19, November 2025 at 2:30 PM ET\u003C\/p\u003E\u003Cp\u003EEngineered Biosystems Building (EBB), CHOA seminar room EBB 1005\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EMeeting link: \u003Ca href=\u0022https:\/\/gatech.zoom.us\/j\/94935218803?pwd=mhRaWhhZYhUNXKs0Mi7LbuCqrvNayd.1\u0022\u003Ehttps:\/\/gatech.zoom.us\/j\/94935218803?pwd=mhRaWhhZYhUNXKs0Mi7LbuCqrvNayd.1\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003Cstrong\u003EThesis Advisor:\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EWilliam Ratcliff, Ph.D.\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECommittee Members:\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EOzan Bozdag, Ph.D.\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EAnnalise Paaby, Ph.D.\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EFrank Rozenweig, Ph.D.\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EJohn Blazeck, Ph.D.\u003C\/p\u003E\u003Cp\u003ESchool of Chemical and Biomolecular Engineering\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EABSTRACT:\u0026nbsp;Evolutionary innovations have shaped the history of life on Earth. This thesis uses synthetic biology and experimental evolution to explore the origin of phototrophic metabolism and the evolution of multicellularity in yeast.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EThe first part of this work examines whether a retinalophototrophic system can be readily acquired by an organism with no prior history of phototrophy. We transformed unicellular \u003Cem\u003ESaccharomyces cerevisiae\u003C\/em\u003E into a facultative photoheterotroph by inserting a rhodopsin into the yeast vacuole, allowing light to translocate protons into the vacuolar compartment, a function typically driven by consuming ATP. We show that yeast-bearing rhodopsins gain a selective advantage when grown under green light, growing more rapidly than their non-phototrophic ancestor. This work demonstrates the remarkable ease with which rhodopsins may be horizontally transferred, providing novel biological function without the need for prior evolutionary optimization.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp;\u0026nbsp; \u003C\/strong\u003ENext, we explored the role of nascent life cycle structures on the evolution of collective-level adaptations. All complex multicellular lineages (animals, plants, brown algae, red algae and fungi) develop clonally and are obligately multicellular. We used \u003Cem\u003ES. cerevisiae\u003C\/em\u003E to engineer a facultative life cycle (alternating between single cell and multicellular clusters) and compared it to obligate multicellularity. Using experimental evolution, we found that all obligately multicellular populations evolved larger multicellular size and tetraploidy, a known multicellular trait. These traits were severely constrained in facultative populations, despite tetraploidy being strongly beneficial across the full life cycle. We show that facultative life cycles create an establishment barrier through population asymmetries due to group formation reducing the number of units of selection, coupled with cell-level selection dominating group-level selection. These findings demonstrate that the presence of a unicellular stage creates genetic barriers to multicellular adaptations, which may explain why facultatively multicellular organisms have remained simple compared to complex multicellularity seen only in obligately multicellular organisms.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003ETogether, this thesis advances our understanding of early steps in evolutionary innovations, with a focus on the origin of phototrophy and the role of obligate life cycles during the transition to multicellularity.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u0026nbsp;\u003Cbr\u003EUsing synthetic biology and experimental evolution to reconstruct major evolutionary innovations\u003Cbr\u003E\u0026nbsp;\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"  Using synthetic biology and experimental evolution to reconstruct major evolutionary innovations"}],"uid":"27707","created_gmt":"2025-11-06 19:28:36","changed_gmt":"2025-11-06 19:29:06","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2025-11-19T14:30:00-05:00","event_time_end":"2025-11-19T16:30:54-05:00","event_time_end_last":"2025-11-19T16:30:54-05:00","gmt_time_start":"2025-11-19 19:30:00","gmt_time_end":"2025-11-19 21:30:54","gmt_time_end_last":"2025-11-19 21:30:54","rrule":null,"timezone":"America\/New_York"},"location":"Engineered Biosystems Building (EBB), CHOA seminar room EBB 1005","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}