Devina Puri
BME PhD Defense Presentation
Date: 2023-02-23
Time: 10am - 12 pm
Location / Meeting Link: HSRB E160; zoom meeting link: https://emory.zoom.us/j/95451595472
Committee Members:
Kyle R. Allison, Ph.D. (Advisor) Wilbur A. Lam, M.D., Ph.D. Sarah W. Satola, Ph.D. Shuichi Takayama, Ph.D. Cheng Zhu, Ph.D.
Title: Single-cell dynamics of self-assembling bacterial communities
Abstract:
Bacteria are unicellular organisms, but they can also form multicellular communities called biofilms. Differing from individual “planktonic” cells, biofilms can better withstand toxic environments, tolerate antibiotic treatment and escape immune response. Hence, biofilms serve as reservoirs for several chronic and recurrent infections, making their study important from a public health standpoint. Genetics of biofilms have been thoroughly investigated and advances in microscopy have provided insights into their structure and physiology. However, the observations of cell-scale morphogenetic events leading to their formation are incomplete. The overall objective of this dissertation was to develop a platform to study multicellular self-assembly in biofilms by tracking their dynamics at the single-cell level. These approaches allowed tracking of the complete morphogenesis at the cell scale in Escherichia coli and led to the discovery of a novel multicellular self-assembly process occurring in this bacterium. This developmental process is initiated as single-cells divide and assemble 4-cell rosettes, which extend into regulated chain-like communities. Each multicellular chain remains clonal and grows up to hundreds of micrometers in lengths, before ultimately stopping growth and attaching to the surface. In this dissertation, we first quantitatively characterized the entire multicellular chain morphogenesis process in E. coli, which demonstrated the assembly of clonal, stable cellular structures with regulated growth dynamics. Secondly, investigation of cellular arrangements in E. coli biofilms showed that parallel-aligned accumulation of clonal cellular chains generated their internal structures. Finally, we investigated the genetics of E. coli chain morphogenesis, which revealed that this process had multiple stages, each of which has a specific genetic regulation. Overall, this research establishes that E. coli, a unicellular bacterium and an important pathogen, can follow a multicellular life cycle. This uncovered process has implications for understanding development of E. coli biofilms, treatment and prevention of bacterial diseases, and the engineering of synthetic multicellular communities.