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Publication Date


First Advisor

David Bickar

Document Type

Honors Project

Degree Name

Bachelor of Arts




Parkinson's disease, Gut microbiome, Dopamine, Dysbiosis, Tyrosine hydroxylase, Enzymes


Gut dysbiosis is a well documented pre-motor symptom of Parkinson’s disease (PD). Various populations of bacteria are found to be out of balance in the guts of PD patients across the world. Among these bacteria are genera with the potential to produce dopamine, a neurotransmitter with a critical role in PD. Sequence analysis was used to compare the genomes of bacteria exhibiting dysbiosis in PD patients, and the sequences of key enzymes in the dopamine biosynthetic pathway, including tyrosine hydroxylase, as well as tyrosine decarboxylase or DOPA decarboxylase. Alternatives to these enzymes were also investigated. The genera Bacteroides and Clostridium were identified as having sequence similarity with tyrosine hydroxylase, tyrosine or DOPA decarboxylase, as well as a tetrahydrobiopterin synthesis enzyme. Although further studies will be necessary to demonstrate that these bacteria have the ability to produce dopamine, and that they can do so while residing in the gastrointestinal tract, this work has laid the foundation for future research on the role of the gut microbiota in PD.


©2021 Arianna Ratih Tidball. Access limited to the Smith College community and other researchers while on campus. Smith College community members also may access from off-campus using a Smith College log-in. Other off-campus researchers may request a copy through Interlibrary Loan for personal use.




75 pages : color illustrations. Includes bibliographical references (pages 56-69)