Ice Nucleation by Marine Psychrophiles

这项研究的主要目的是调查极地海洋嗜冷细菌的潜在核冰在实验室中使用微生物，分子生物学和大气科学的方法相结合。关于嗜冷生物如何与冰相互作用和科普冰或它们对极端寒冷和盐度条件的适应，人们知之甚少。这项工作将涉及一系列实验室实验，使用一种新的冷冻管技术测定冷冻光谱，这将提供以下方面的定量信息：（i）含有海冰细菌的非均匀冷冻液滴的温度依赖性冷冻速率，（ii）海冰细菌分离物中冰核活性与防冻活性的比例，以及（iii）温度-在一定温度和盐度范围内生长的具有冰核活性的细菌的依赖性冷冻速率。将确定引起所观察到的活动的化合物，这是发展可在实地应用于南极水和云样本的原位细菌冰核检测分析的重要一步。这项工作的目标之一是更好地了解极地海洋细菌在海冰冻结条件下的生存和冷适应过程。由于海冰强烈影响极地和全球气候，这项研究具有重要意义，因为它还将为评估细菌冰成核在海冰形成中的重要性提供数据。这些对冰成核率的测量将是对嗜冷海洋细菌的第一次高分辨率测量。另一个目标是通过对在北极和南极地区发现的云细菌的成核率进行高分辨率测量，更好地了解极地云中细菌冰形成过程的影响。初步测量表明，这些细菌在较温暖的温度下使冰成核，在极地地区的影响可能非常重要，因为冰可以强烈影响云动力学，云辐射特性，降水形成和云化学。如果这些初步测量得到证实，这里收集的数据将对提高对极地云过程和模型的理解非常重要。第三个目标是通过表征冰核化合物并将其与已知的植物来源的冰核细菌进行比较，更好地了解海洋细菌冰核的分子基础，这是迄今为止详细研究的唯一冰核细菌。拟议的活动将支持博士后研究人员的学术生涯开始，并将作为几个本科生实验室项目的基础。 这项研究的结果将广泛发表在各种科学期刊和宣传场所。

The primary objective of this research is to investigate polar marine psychrophilic bacteria for their potential to nucleate ice using a combination of microbiological, molecular biological and atmospheric science approaches in the laboratory. Very little is known about how psychrophiles interact and cope with ice or their adaptations to conditions of extreme cold and salinity. This work will involve a series of laboratory experiments using a novel freeze-tube technique for assaying freezing spectra which will provide quantitative information on: (i) the temperature-dependent freezing rates for heterogeneously frozen droplets containing sea-ice bacteria, (ii) the proportional occurrence of ice-nucleation activity versus anti-freeze activity among sea-ice bacterial isolates and (iii) the temperature-dependent freezing rates of bacteria with ice-nucleation activity grown at a range of temperatures and salinities. The compound(s) responsible for the observed activity will be identified, which is an essential step towards the development of an in-situ bacterial ice-nucleation detection assay that can be applied in the field to Antarctic water and cloud samples. One of the goals of this work is to better understand survival and cold adaptation processes of polar marine bacteria confronted with freezing conditions in sea ice. Since sea ice strongly impacts polar, as well as the global climates, this research is of significant interest because it will also provide data for accessing the importance of bacterial ice nucleation in the formation of sea ice. These measurements of ice-nucleation rates will be the first high-resolution measurements for psychrophilic marine bacteria. Another goal is to better understand the impact of bacterial ice initiation processes in polar clouds by making high-resolution measurements of nucleation rates for cloud bacteria found over Arctic and Antarctic regions. Initial measurements indicate these bacteria nucleate ice at warmer temperatures and the effect in polar regions may be quite important, since ice can strongly impact cloud dynamics, cloud radiative properties, precipitation formation, and cloud chemistry. If these initial measurements are confirmed, the data collected here will be important for improving the understanding of polar cloud processes and models. A third goal is to better understand the molecular basis of marine bacterial ice nucleation by characterizing the ice-nucleation compound and comparing it with those of known plant-derived ice-nucleating bacteria, which are the only ice-nucleating bacteria examined in detail to date. The proposed activity will support the beginning academic career of a post-doctoral researcher and will serve as the basis for several undergraduate student laboratory projects. Results from this research will be widely published in various scientific journals and outreach venues.