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

有些细菌具有惊人的催化水冻结的能力。这些细菌甚至可能促成云中降水的形成。关于细菌如何以及为什么获得这种能力，人们知之甚少。在科学术语中，这种能力被称为冰核活动。在这个项目中，科学家们将研究最近从降水中分离出来的细菌Lysinibacillusparviboronicapiens，它会分泌一种尚未确定的具有冰核活性的分子。科学家们建议识别合成这种分子所必需的基因，研究细菌通常生活在哪里，以及它如何从冰核活动中受益。长期目标之一是了解这种分子用来成核冰的详细机制。这一知识可以提高我们预测降雨量和频率、影响天气、在干旱期间增加降雨量或防止破坏性冰雹风暴的能力。该项目的教育宣传部分包括三个方面：向阿巴拉契亚高中生传播和教授冰核科学，以增加知识并激发他们对未来可能的科学机会的兴趣；未被充分代表的本科生将参与研究计划；研究生将接受关于冰核的高级培训，在整个研究生生涯中接受指导，并产生可通过学术出版物传播的数据。将评估该项目的有效性，不仅是开展拟议的研究活动，而且是培训和向三个目标受众传播信息的能力。纯净水在结冰之前过冷到大约-40摄氏度。只有在存在具有冰核活性(INA)的粒子(称为冰核)的情况下，水才能在较高的温度下冻结。在非热带气候中，云中的冰核催化水滴冻结，形成降水。间接证据表明，生物冰核是云中冰成核的贡献者。除了一种单一类型的细菌INA蛋白外，人们对生物INA分子以及INA的进化及其在生物体生命周期中的作用知之甚少。微小溶血杆菌(Lysinibacillusparviboronicapiens，LP)最近被鉴定为第一株具有INA的革兰氏阳性细菌。对Lp的INA的初步鉴定表明，该活性具有耐热、耐蛋白酶、分泌和水溶性的特点。本项目有以下目标：1.鉴定和表征Lp INA分子的生物合成途径并表征分子本身；2.揭示潜在的生物合成途径的进化历史；3.确定该分子在Lp生态中的作用。实现这些目标将提供有关有机体如何改变其生存环境的新知识。由于冰核在大气过程中的假设作用，该项目还可能提高我们对细菌如何影响降雨量和强度的理解，从而有助于阐明细菌在影响地球气候方面可能发挥的作用。对本科生和研究生的培训，对高中的推广和教育，以及对培训和推广部分的评估，补充了该项目的实验方面。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

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.