The Characterization of the Novel Gene CIA7 Using Pb Exposed Wild-Type and Mutant Strains of Chlamydomonas Reinhardtii

Industrialization has increased the risk of heavy metal contamination. This leads to contamination of the ecosystem surrounding microalga and other primary producers. Chlamydomonas reinhardtii is a unicellular alga that is of interest in toxicity studies due its detoxification pathways. This study aims to compare three common markers of cellular health and heavy metal homeostasis namely, levels of Pb bioaccumulation, chlorophyll fluorescence, and cell size between two strains of C. reinhardtii: a wild type (CC4425) and a mutant (CC5013). The mutant strain has a gene designated as Cia7 that has been disrupted by Ble insert. Cia7’s cysteine rich protein product (CIA7) is hypothesized to provide increased heavy metal tolerance to C. reinhardtii, due to its structural similarities to known thiol-peptides such as phytochelatins and metallothioneins. Levels of bioaccumulated lead were analyzed using inductively couple plasma optical emission spectrometry. Differences in chlorophyll fluorescence were determined using flow cytometry, while changes in cell size were determined under scanning electron microscopy. The results of this study show that CC5013 accumulated more lead than CC4425 and exhibited marked reductions in both chlorophyll fluorescence and cell size across increasing concentrations of lead. These results lend support to the hypothesis that Cia7’s cysteine rich protein product (CIA7) could provide increased heavy metal tolerance to C. reinhardtii