Collaborative Research: An Integrated Approach to Understanding the Function of the Potent Hepatotoxin Microcystin in the Growth & Ecology of Microcystis

点击翻译按钮获取中文摘要

Blooms of toxic photosynthetic bacteria (cyanobacteria) are occurring globally with expanding frequency, duration and intensity in lakes, reservoirs and river systems. Most recently blooms of the toxic cyanobacterium Microcystis shut down the water supply of the city of Toledo, OH for a weekend in August of 2014. While the scientific community has developed a solid understanding of the factors that contribute to the blooms of Microcystis, previous research has not explained why cells make the hepato- (liver) toxin microcystin. As a potent inhibitor of a key class of enzymes - protein phosphatases - microcystin might play important roles inside Microcystis cells, and once released, inside the cells of other (target) organisms. This project will use advanced tools in molecular biology (RNA sequencing), microbial genetics, the quantification of small metabolites (metabolomics) and enzyme analyses to understand how the presence of microcystin shapes the activity of both the cells that make the compound and the community of microorganisms around them. Experiments in the laboratory will be complemented by field surveys of bloom events across naturally occurring toxin gradients - areas of historically high and low concentrations of toxin during the summer bloom season. State-of-the-art statistical analyses combined with these advanced scientific approaches will transform the understanding of why these cyanobacteria make this toxic compound. Understanding of the biological functions of the microcystin, will lead to better stewardship of a valuable natural resource: potable water. The total research effort will train students, including those from underrepresented groups, and broadly disseminate information to the public, systems managers and the scientific community. A significant component will feed into state-associated, in-class 4H training that will expose as many as 200,000 students to cyanobacteria as a model system to examine complex biochemical questions.The goal of this project is to develop a deeper understanding of the biochemical role of microcystins, a potent protein phosphatase inhibitor, within cells and communities, and address both ecological and evolutionary questions concerning the maintenance of this and other expensive biosynthetic pathways for non-ribosomally encoded secondary metabolites within a (sub)population of cells. To determine how microcystin shapes cellular biochemistry and physiology, controlled lab experiments with Microcystis isolates that make microcystin, engineered strains where the biosynthetic gene has been knocked out, and wild-type Microcystis cells that lack the biosynthetic pathway will be conducted. Other cyanobacterial pairs (Planktothrix and Anabaena spp.) that make or do not make the toxin, engineered bacteria that produce this compound and a set of microorganisms isolated from Lake Erie that co-occur with Microcystis and may be influenced by toxin will also be tested. Experiments in the presence and absence of exogenous toxin will be conducted with both producers and non-toxin producers. State-of-the-art techniques in metabolic (LC-MS and LC-MS/MS metabolomics and lipidomics), transcriptional (Illumina mRNA-sequencing), enzymatic (4:3:3-regulated processes) and physiological analyses (e.g., cellular growth rates, primary production, and photosynthetic efficiency) for these defined lab strains will be employed to develop "fingerprints" of cellular function and elucidate how microcystin shapes these biochemical pathways and the physiological ecology of these cells. Lab experiments will be complemented by field surveys of bloom events across naturally occurring and well documented toxin gradients. Relationships will be identified using univariate and multivariate techniques. This novel integration of sequencing, small molecule chemistry, physiological and enzymatic approaches will permit the mapping of the physiological biochemistry of cells and identify both isolated as well as synergistic effects: indeed this work may transform the study of secondary metabolites in complex microbial systems and provide insights into microbial evolutionary ecology.