Date of Completion

Spring 5-1-2024

Thesis Advisor(s)

Marcy J. Balunas

Honors Major

Pharmacy Studies

Disciplines

Environmental Microbiology and Microbial Ecology | Medicinal and Pharmaceutical Chemistry | Natural Products Chemistry and Pharmacognosy

Abstract

Microbes are a fruitful source of natural product drug discovery since many of their secondary metabolites show defensive activity and have unique structures. However, extracting and elucidating the structure of those compounds can be challenging in vitro due to particular environmental and nutritional requirements of some bacteria. Those requirements may include proximity to other organisms that the microbes have symbiotic relationships with. Under those conditions, the organism may activate silent biosynthetic gene clusters (BGCs) responsible for production of certain secondary metabolites not typically expressed otherwise. One method of BGC induction is co-culturing with other microbes since this mimics the natural environment and interactions of the organism. Here we focus on the relationships between the Hawaiian bobtail squid, Euprymna scolopes, and its symbiotic bacteria as a method of inducing BGCs. E. scolopes possesses two organs of interest for microbiome research: a light organ colonized by a monoculture of Vibrio fischeri and an accessory nidamental gland (ANG), a reproductive organ, colonized by a consortium of bacteria. Given the microbial separation between the two organs, we hypothesized that ANG bacteria and V. fischeri may be producing defensive secondary metabolites preventing the spread of bacteria from one organ to the other. Co-cultures and monocultures of ANG- associated bacteria and V. fischeri were performed to analyze possible upregulation and downregulation of metabolites produced by the ANG bacteria. Liquid chromatography-mass spectrometry (LC-MS) and metabolomic data showed modulation of secondary metabolites as a result of co-culturing. The co-cultures each exhibited upregulation of unique metabolites not present in either monocultures; e.g., the ANG-1 co-culture possessed 109 unique features. Of these extracts, some also exhibited preliminary bioactivity against Vibrio strains.

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