Date of Defense

Summer 8-8-1997


Biological Sciences

First Advisor

Silvia Rossbach, Biological Sciences

Second Advisor

Bruce Bejcek, Biological Sciences

Third Advisor

Mark Galbraith, Biological Sciences


As a result of industrial pollution and poor methods of waste disposal, heavy metals such as copper, cadmium, and mercury, have accumulated in the environment. These metals cannot be mineralized into nontoxic coompounds (Barkay et al., 1992) and they may be ingested and accumulate in organisms where they may cause acute to fatal illness (Ron et al., 1992). Although most studies have dealt with the effects of these metals in higher eukaryotes, the presence of these hazardous metals creates a stressful environment for soil microorganisms as well. In this thesis, the author describes the use of a transposon carrying the lacZ gene to create P. fluorescens mutant strains. A total of 5000 mutants were screened for differential gene activity on media supplemented with metal, and seventeen mutant strains contained gene fusions that were regulated in the presence of Cd. The author has characterized thirteen mutant strains that displayed higher gene expression after metal exposure, whereas four mutant strains showed reduced gene expression under the same conditions. Additionally, several of these mutant strains showed similar differential gene activity in the presence of copper (Cu) or zinc (Zn).

Access Setting

Honors Thesis-Campus Only