Although the toxic cyanobacterium Microcystis continues to be the focus of studies around the globe, scientists remain unable to definitively answer the question 'what makes Microcystis bloom?' Using genomic and proteomic information, researchers at the University of Tennessee and Oak Ridge National Laboratory will collect 'snapshots' of the biochemical pathways that are simultaneously active in Microcystis cells before, during, and after bloom conditions. By comparing these pathways with lab cultures grown under controlled conditions, researchers will be able to for the first time tease apart the complicated interactions between the environment and Microcystis population growth. To accomplish this goal the researchers will integrate new data sets of recently completed genomic sequences of Microcystis with state-of-the-art tools that analyze whole cell and community protein expression. The resulting information will provide an accurate map of the physiological status of cells under different growth conditions as well as during bloom formation, climax and termination. The work will also provide information on how the environment influences cellular pathways, an important step in understanding the connections between ecological organism response and cellular biochemical processes.
The project will facilitate outreach and diversification at an EPSCoR Institution (The University of Tennessee) and provide training for undergraduate and graduate students. The PIs will continue to engage underrepresented groups in the research and will disseminate results to the public through science-focused journalism interns.
The project focused on using advanced techniques in molecular biology to examine how the genes and their products (RNA and proteins) of a toxic cyanobacterium, Microcystis, change during growth under different conditions in the laboratory as well as during massive proliferations (algal blooms) in the field. This cyanobacterium is perhaps the greatest global threat to our freshwater resources, as it appears on all of the continents except Antarctica and is the cause of massive algal blooms in bodies of water ranging from small ponds to the Laurentian Great Lakes in North American as well as in regions around the world. The study pointed to a potential for a previously understudied source of nitrogen, urea, as a potential culprit in the expansion of these bloom events. It also demonstrated how cells respond to changes in their environment by massively changing genetic regulation in order to maintain metabolic homeostasis (in a manner akin to how the heating-ventilation-air condition systems are always changing to maintain a comfortable temperature in a building). This project also advanced our understanding of how microbial communities work together to shape the environment we perceive: studies of metagenomes (the cumulative DNA content of all the cells in a sample) demonstrated that similar genetic functions were present in toxic cyanobacterial blooms at different locations in North America as well as in China, although the actual organisms with the ability to carry out these functions changed. Finally, this work has shown that activity of Microcystis to adapt to different conditions might be in part controlled by transposable genetic elements (i.e., mobile DNA fragments of "jumping genes") whose activity in turn appears to at least in part be regulated by the nutrients that are provided to cells. Overall the study provides answers to questions concerning the complex genomic architecture seen in attempts to sequence Microcystis genomes, and in turn raises new questions concerning how Microcystis cells respond to their own environment during bloom events. At the time of this writing this project has resulted in 13 peer-reviewed publications and led to the training of 2 postdoctoral associates, 3 graduate students and 6 undergraduate research interns. Presentations at numerous conferences, including a series of keynote and plenary addresses by the PI, have disseminated information to both the scientific community as well as ecosystem stewards, government agencies and the general public.
