Honors Theses
Date of Award
Spring 5-11-2024
Document Type
Undergraduate Thesis
Department
Biology
First Advisor
Patrick Curtis
Second Advisor
Wayne Gray
Third Advisor
Brice Noonan
Relational Format
Dissertation/Thesis
Abstract
Caulobacter crescentus is a model bacterium for its unusual life cycle. This cycle features three distinct phases- the stalked stage, pre-divisional or actively dividing stage, and the swarmer stage, characterized by the production of a flagellum and multiple pili. Pili are necessary for cell attachment to surfaces and their reuptake into the cell can help drive the cell cycle forward. The gene that encodes the pilus subunit, pilA, is regulated by four binding sites for the cell cycle regulator CtrA. Previous research has determined that one site induces expression while two of the four sites inhibit expression. It is unknown why C. cresentus evolved this mechanism. To investigate this mechanism’s function, the inhibitory binding sites were mutated to prevent CtrA binding. The altered timing of pilus production was tested through a bead-pulldown experiment to determine the cell stage(s) at which pili are produced. The results show that mutation of CtrA binding inhibitory sites produced more pre-divisional cells expressing pili. The in vivo consequence of altered timing was tested using a phage survivability assay. This assay showed that cells with earlier pili production were more sensitive to a pilitropic phage φCbk, having a lower survival rate. This is noteworthy, as this suggests that C. crescentus may have evolved this regulatory mechanism as a defense against φCbk. Further research is required to determine the effects of this mutation on cell attachment and progression through its cell cycle.
Recommended Citation
Johnson, Eli, "Cell Cycle Regulator Delays Pilus Production in Caulobacter Crescentus" (2024). Honors Theses. 3059.
https://egrove.olemiss.edu/hon_thesis/3059
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