Analysis of toxin production by cyanobacteria

• Main Author: Tan, Jia Hann.
• Other Authors: Gin Yew-Hoong Karina
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Environmental engineering
• Online Access: http://hdl.handle.net/10356/39443
• Institution: Nanyang Technological University

Eutrophication problems exist in the Kranji Reservoir and studies have been carried out to understand the situation and to obtain an effective remediation for the problem. It has been found that there are two main cyanobacteria responsible for the eutrophication, Microcystis and Anabaena. Microcystin, which is a toxin produced by Microcystis, have several negative effects on health and exposure to certain levels poses severe health risk to both humans and animals. Several studies have been done to study the factors affecting toxin production of Microcystis, mainly temperature and light intensity. Some studies have shown that light quality also affects the production of toxin. Thus, this project aims to study the effect that light quality has on toxin production and its correlation to cell growth, chlorophyll-a and gene copy number. Cultures in the experiment underwent a purification process using sulphide gradient method. After which, they were cultivated in four different environment setups, ambient (control), red light, green light and blue light. Cultures were placed within metal frames which were wrapped in translucent colored paper of the required color, thus, blocking out other wavelengths of light. The cultures of the different cultures were grown under average temperature of 21oC and the range of light intensity was between 19 µmol/m2/s and 30 µmol/m2/s. Samples were drawn periodically and tests were carried out to determine the toxin concentration, cell number, chlorophyll-a concentration, phycobilin concentration. The toxin concentration was found to be at least halved when cultures were subjected to the three light wavelengths, red, green and blue. Positive and negative correlation were found to exist between toxin concentrations with gene copy number concentration and toxin concentrations with cell number concentration, while a linear positive correlation was observed between toxin concentrations and chlorophyll-a concentrations. It was also found that cell growth rate appears to limit toxin production rate. As the apparatus and set up were not very precise, this project could also determine the general trend. Thus, further investigation should be carried out under controlled set up with more precise testing to achieve better results and understanding.