Chemically Mediated Algal-Bacterial Interactions: Promotion & Inhibition

Author

Kara Talbott, University of the PacificFollow

Date of Award

2023

Document Type

Thesis

Degree Name

Master of Science (M.S.)

Department

Pharmaceutical and Chemical Sciences

First Advisor

Skylar Carlson

First Committee Member

Melany Puglisi-Weening

Second Committee Member

Jerry W. Tsai

Abstract

Algae-bacteria interactions range from mutualistic, Chlamydomonas reinhardtii (green algae) provides carbonate complexes for surface associated bacteria (SAB) and the bacteria in turn provide B-12 for the algae, to pathogenic, the presence of certain bacteria increases the incidence of bleaching in the algae. Algal natural products have been found to display the following activities: anti-fouling, anti-bacterial, anti-cancer, and anti-feedant. Separately, it has been well documented in the literature that algae mediate their SAB, also known as their microbiome, using natural products to attract and inhibit different bacterial strains. My graduate work builds on these findings; our hypothesis is that the algal-bacterial interactions of California algae from Stinson Beach, La Jolla, and Santa Cruz and their SAB are chemically mediated.Starting with algae collected from the surf and intertidal region, small blades of algae were spread on nutrient rich agar. Individual bacteria were then isolated, and their morphologies were compared. Between nine and eleven unique morphologies were found from each location. Removing duplicates and highlighting diversity of morphologies, several isolates from each location were identified by sequencing the DNA that encodes for the nine hypervariable regions (V1-V9) of the 16S-rRNA. The forward and reverse sequences returned from Sanger sequencing were aligned using Clustal Omega and input into the NCBI blastN database and assembled into a phylogenetic tree using Clustal Omega. The remaining algae sample was used to identify the genus and species using a dichotomous key based on their morphology from the book “Pacific Seaweeds: A Guide to common Seaweeds of the West Coast” by Druehl and Clarkston. The algae samples were then exhaustively extracted in 50:50 methanol:ethyl acetate. Algal extracts were then screened at 75 µg/mL for growth promotion or inhibition against the isolated surface associated bacteria observing the growth of each well at 13 h and 24 h using a Tecan plate reader. The growth assays showed mixed results when the surface associated bacteria were tested against the extracted algae they were isolated from. We hypothesize that the chemical mediation of the microbiome by the algae is a significant factor in regulating the settlement of different bacteria. I will present my research to complete these aims, a detailed discussion of my findings and future directions of this project before publication.

Pages

59

Recommended Citation

Talbott, Kara. (2023). Chemically Mediated Algal-Bacterial Interactions: Promotion & Inhibition. University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/uop_etds/4260