Date of Award


Document Type


Degree Name

Master of Science (MS)


College of Science and Mathematics



Thesis Sponsor/Dissertation Chair/Project Chair

Lee H. Lee

Committee Member

Bonnie Lustigman

Committee Member

Quin C. Vega


Anacystis nidulans is a rod-shaped, freshwater cyanobacterium. Like other cyanobacteria, it is an obligate photoautotroph that is similar to gram-negative bacteria in cell wall structure, replication and ability to harbor plasmids. Anacystis nidulans is often used as an indicator of the presence and level of pollutants in the environment. Mercury, iron, cadmium, and zinc are among the heavy metal contaminants found in the environment and in bodies of freshwater through industrial discharges, agricultural runoff and sewage treatments. In very low concentrations, they do not pose any threat to the environment, but high concentrations can be lethal. Different microorganisms vary in their tolerance to heavy metals based on exposure and physiological and/or genetic mechanisms.

In this study, the combined effects of the heavy metal iron with cadmium, mercury, or zinc were used to study their effects on the growth of A. nidulans. The concentration of iron used was 10 mg/L for all studies done. However, varying concentrations of cadmium, zinc and mercury were used in combinations with the constant iron concentration. The concentrations of cadmium used were 5, 10, 20, 25, 50 mg/L. For zinc, the concentrations used were 10, 25, 50, and 75 mg/ L. Concentrations of mercury used were much lower, 0.5, 1, 5 and 10 mg/L, because mercury is known to be the most toxic heavy metal. For the study of the combined effects of iron and mercury, several passages were done; and some resistant cells were observed and isolated. The resistant cells were used to conduct preliminary research on locating the heavy metal resistance genes. The results of the plasmid miniprep suggested that there might be an induced expression of a plasmid, which may be linked to resistance. Additional research must be done to further understand the mechanisms of heavy metal resistance in A. nidulans.

File Format


Included in

Biology Commons