{"689716":{"#nid":"689716","#data":{"type":"event","title":"PhD Defense by Christopher Zhang","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 Quantitative Biosciences\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\u003EChristopher Zhang\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EWill defend his thesis\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u201cTHE COSTS AND CONSTRAINTS OF BIOLOGICAL COMPLEXITY\u201d\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EApril 22nd,\u0026nbsp;2026\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E2:00 PM\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EDALNEY 180\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022https:\/\/gatech.zoom.us\/j\/98792482360?pwd=DLP1U5pLjGt6ssC3iJWXqxL24ylm5f.1\u0022\u003Ehttps:\/\/gatech.zoom.us\/j\/98792482360?pwd=DLP1U5pLjGt6ssC3iJWXqxL24ylm5f.1\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003EMeeting ID: 987 9248 2360\u003C\/p\u003E\u003Cp\u003EPasscode: Crisis\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EThesis Advisors:\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EDr. Brian K. Hammer\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\u003EDr. William C. Ratcliff\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\u003EDr. Samuel P. Brown\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\u003E\u0026nbsp;\u003C\/strong\u003EDr. Peter J. Yunker\u003C\/p\u003E\u003Cp\u003ESchool of Physics\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003EDr. Lauren Speare\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003EGeorgia Institute of Technology\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAbstract:\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EThe costs and constraints of biological complexity are central to understanding how sophisticated traits and communities evolve and persist. In this dissertation defense, I will present two stories involving the Type Six Secretion System (T6SS), a complex bacterial apparatus that allows a bacterium to kill an adjacent competitor with remarkable efficiency. T6SSs have been shown to strongly impact microbial population dynamics, and there is an ongoing effort to understand exactly how this occurs.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EFirst, I will describe my efforts to precisely measure the metabolic cost of utilizing the T6SS, showing that this cost is significantly lower than prior expectations. Then, I will present a combined effort to scan the entire bacterial phylogenetic tree to identify which and how many bacteria actually possess the T6SS, revising a widely cited estimate that has stood for nearly two decades. Together, these two studies refine our understanding of the T6SS as a whole and reshape how we think about the role of bacterial weaponry in shaping microbial dynamics over evolutionary timescales.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cstrong\u003ETHE COSTS AND CONSTRAINTS OF BIOLOGICAL COMPLEXITY\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"THE COSTS AND CONSTRAINTS OF BIOLOGICAL COMPLEXITY"}],"uid":"27707","created_gmt":"2026-04-13 18:13:00","changed_gmt":"2026-04-13 18:13:47","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2026-04-22T14:00:00-04:00","event_time_end":"2026-04-22T16:00:00-04:00","event_time_end_last":"2026-04-22T16:00:00-04:00","gmt_time_start":"2026-04-22 18:00:00","gmt_time_end":"2026-04-22 20:00:00","gmt_time_end_last":"2026-04-22 20:00:00","rrule":null,"timezone":"America\/New_York"},"location":"DALNEY 180","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":""}}}