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

John Gaynor

Committee Member

Carlos Molina


Heavy metal resistance within cyanobacteria is often observed because cyanobacteria are good indicators of pollutants in the environment. Their ability to recognize the presence of many heavy metals makes cyanobacteria an important source of study. Cadmium is one of the most toxic heavy metals. Cadmium inhibits spontaneous protein folding, binds to sulphydryl groups (found in nucleic acids, proteins, and enzymes), and outcompetes essential metals for important binding sites. The effects of cadmium (CdCl2) on the growth and coupled permeability of Synechococcus sp. IU 625 was shown to inhibit Syn. sp. IU 625 cells at CdCl2 concentration 30 mg/L and to possess low permeability to cells, respectively. Zinc is one of the essential metals involved within the domains of many enzymes, DNA binding proteins, and zinc-finger motif proteins. However, zinc is toxic at high concentrations. The growth of Syn. sp. IU 625 cells was shown to be inhibited at zinc (ZnCl2) concentration 50 mg/L after 1st and 2nd passage studies were performed. Zinc was shown to be permeable to Syn. sp. IU 625 cells at ~ 50% permeability. Exopolysaccharides are polymeric carbohydrates that have been known to be produced as a response to stress or toxicity. Exopolysaccharide production as a reaction to heavy metals zinc (ZnCl2), cadmium (CdCl2), mercury (HgCl2), and copper (CuCl2) was evaluated within Syn. sp. IU 625 cells and was shown to be specific to the type of heavy metal present. It will be important to evaluate a resistance mechanism to high zinc concentrations by the actions of a CPx-ATPase efflux pump (ZiaA-like protein) and its regulator repressor (ZiaR-like protein) within cyanobacterium, Synechococcus sp. IU 625. A ZiaA-like protein and ZiaR-like protein were shown to be present within Synechococcus sp. IU 625 genome and to possess high homology to closely related species Synechococcus elongatus PCC 7942 and Synechococcus elongatus PCC 6301. The quantitative expression of a ZiaA-like protein was shown to be present within Synechococcus sp. IU 625 as a function of time and zinc concentration.

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