Microcystis aeruginosa is the dominant cyanobacterial species causing harmful algal blooms in lakes and estuarine water bodies worldwide. The blooms release potent toxins and pose severe public health hazards to humans using the water, including sickness and death. Despite the devastating effects, currently there is remarkably little understanding of the M. aeruginosa biology regulating bloom formation and toxin production. Thus research is much needed to develop more effective controlling strategies for M. aeruginosa blooms based on the understanding of basic biology. The focus of the proposed research is quorum sensing, the key cell-cell communication mechanism via chemical "languages", which control population behaviors such as toxin production and cell growth in diverse bacteria, but is poorly understood in M. aeruginosa. The understanding of the basic biology of Microcystis quorum sensing will lead to novel strategies for controlling M. aeruginosa blooms in various water bodies by modulating the quorum sensing pathways. The education program targets local high school students and the undergraduate and graduate students at the University of Texas at San Antonio, a Hispanic serving institution with about 60 % underrepresented minorities.
Preliminary results have identified two chemical "languages", also called autoinducers, including N-acyl homoserine lactones and autoinducer-2 in M. aeruginosa. Building on these findings, the proposed research will be performed to elucidate the mechanisms of quorum sensing in regulating bloom formation and toxin production. The PI will approach these studies by elucidating the N-acyl homoserine lactones and autoinducer-2-induced quorum sensing pathways in M. aeruginosa. Specifically, the synthase genes responsible for synthesis of N-acyl homoserine lactones and autoinducer-2 will be cloned and the physiological responses regulated by N-acyl homoserine lactones and autoinducer-2 will be identified. Then the PI will dDetermine whether there is crosstalk among quorum sensing, toxin production and cell aggregation. The crosstalk will be validated by blocking each function and examine the effects on the other two functions. And, finally the PI will examine the role of quorum sensing in the development of M. aeruginosa blooms. The focus is on examining the role of quorum sensing in the interaction between M. aeruginosa and other heterotrophic bacteria, an important component of bloom formation. At the conclusion of the study, a better understanding of biological mechanisms of M. aeruginosa blooms will be achieved. The pathways of quorum sensing in M. aeruginosa will be determined including identification the chemical structures of the autoinducers and the genes responsible for synthesizing the autoinducers. Whether toxin production, cell aggregation, cell growth and cell buoyancy are among the social behaviors regulated by the quorum sensing autoinducers will be determined. More importantly, whether quorum sensing contributes to the interaction between M. aeruginosa and heterotrophic bacteria and hence the development of M. aeruginosa blooms will be determined. Overall, this will contribute to answering the question "what causes M. aeruginosa blooms" that has long puzzled the field.
