Unraveling mechanism and ecological role of non-proteinaceous ice nucleation activity in a Gram-positive bacterium

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Some bacteria have the surprising ability to catalyze the freezing of water. These bacteria may even contribute to the formation of precipitation in clouds. Little is known about how and why bacteria acquired this ability, which in scientific terms is called ice nucleation activity. In this project, scientists will study the bacterium Lysinibacillus parviboronicapiens, which was recently isolated from precipitation and which secretes a yet unidentified molecule with ice nucleation activity. The scientists propose to identify the genes that are necessary to synthesize this molecule, to study where the bacterium typically lives, and how it benefits from ice nucleation activity. One of the long-term goals is to understand the detailed mechanism this molecule uses to nucleate ice. This knowledge could improve our ability to predict amount and frequency of precipitation or to influence weather increasing rainfall during droughts or preventing damaging hail storms. The educational outreach components of the project are three-fold: the science of ice nucleation will be disseminated and taught to Appalachian high school students to increase knowledge and stimulate interest of possible scientific opportunities in their future; under-represented undergraduate students will participate in research programs; and graduate students will receive advanced training on ice nucleation, be mentored throughout their graduate school career, and produce data that can be disseminated via scholarly publications. The project will be evaluated on its effectiveness to not only conduct the proposed research activities but its ability to train and disseminate information to the three target audiences. Pure water super-cools to approximately -40°C before it freezes. Only in the presence of particles with ice nucleation activity (INA), called ice nuclei, can water freeze at warmer temperatures. Ice nuclei in clouds in non-tropical climates catalyze the freezing of water droplets that become precipitation. Circumstantial evidence points to biological ice nuclei as contributors to ice nucleation in clouds. Besides a single type of bacterial INA protein, little is known about biological INA molecules and about the evolution of INA and its role in the life cycle of organisms. Lysinibacillus parviboronicapiens (Lp) was recently identified as the first Gram-positive bacterium to have INA. Initial characterization of the INA of Lp revealed this activity to be heat-resistant, proteinase-resistant, secreted, and water-soluble. This project has the following objectives: 1. Identify and characterize the biosynthetic pathway of the Lp INA molecule and characterize the molecule itself, 2. Unravel the evolutionary history of the underlying biosynthetic pathway, 3. Determine the role of the molecule in the ecology of Lp. Accomplishing these objectives will provide new knowledge of how organisms can change the environment in which they live. Because of the hypothesized role of ice nucleation in atmospheric processes, this project may also improve our understanding of how bacteria influence amount and intensity of precipitation and, therefore, help elucidate the possible role of bacteria in influencing earth's climate. Training of undergraduate and graduate students, outreach and education to high schools, and assessment of the training and outreach components complement the experimental aspects of the project. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.