Using transgenic Caenorhabditis elegans as a bioindicator: a useful tool for examining potential environmental hazards, or just a bunch of glowing worms?

Graduation Date

2012

Document Type

Thesis

Program

Other

Program

Thesis (M.S.)--Humboldt State University, Biology, 2012

Committee Chair Name

Bruce A. O'Gara

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Humboldt State University -- Theses -- Biology, Green fluorescent protein, Elegans, Bioindicator, Caenorhabditis, Biomarker, Transgenic, GFP

Abstract

A total of 17 transgenic strains of Caenorhabditis elegans were evaluated for use as bioindicators for the presence of toxins in an environmental sample. Every strain used had Green Fluorescent Protein (GFP) production driven by the promoter region of a gene known to be involved in stress response, metabolism, or development. Controlled exposures were performed on each strain using 22 environmental toxins and contaminants. Changes in GFP intensity between exposed groups and controls were considered proof of changes in that genes expression pattern as a direct result of exposure to the toxin. The goal was to construct expression profiles for each strain using the chosen toxins. The strains could then be used to evaluate environmental samples for the presence of unknown toxins with the expression profiles serving as a preliminary indicator of the amount and type of toxin present. The metallothionein-linked strain CL 2122 showed significant upregulation in the Mtl-2 gene following exposure to 10, 50, and 100 μM cadmium, copper, and lead. This strain also exhibited significant downregulation of metallothionein expression following exposure to diazinon, hexazinone, iron (II) sulfate, paraquat, and piperonyl butoxide, which exemplifies how even a metals-specific stress response can be altered by certain toxins to yield difficult to interpret results. Initially it was thought that a panel of 6-8 strains could be formed that showed clear expression profiles to common environmental pollutants and used to examine samples that had unknown toxins. It was envisioned that the panel would have at least 2 strains that are metals-responsive, two strains that are general organic toxin-responsive, and two strains that are endocrine disruptor and/or estrogen sensitive. This proved to be unrealistic for the genes examined as no strain yielded results that were totally unambiguous. The results indicated that single-gene biomarker-based bioassays could only be used in limited situations, such as large single-toxin releases, or when identifying the exact toxin is not as important as assessing the overall safety of the sample in question.

https://scholarworks.calstate.edu/concern/theses/k930c0550

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