Ice Nucleation by Marine Psychrophiles

本研究的主要目的是在实验室中结合微生物学、分子生物学和大气科学方法，研究极地海洋嗜冷细菌成核冰的潜力。关于嗜冷菌如何相互作用和应对冰，以及它们如何适应极端寒冷和盐度的条件，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来分析冷冻光谱，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冻结率，（ii）海冰细菌分离株中冰成核活性与抗冻活性的比例，以及（iii）在一系列温度和盐度下生长的具有冰成核活性的细菌的温度依赖冻结率。将确定导致所观察到的活性的化合物，这是开发一种可应用于南极水和云样品的原位细菌冰核检测方法的关键步骤。这项工作的目标之一是更好地了解极地海洋细菌在海冰冰冻条件下的生存和寒冷适应过程。由于海冰强烈影响极地以及全球气候，因此这项研究具有重要意义，因为它还将为了解细菌冰核在海冰形成中的重要性提供数据。这些冰核速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结冰过程的影响。最初的测量表明，这些细菌在较高的温度下形成冰核，并且在极地地区的影响可能相当重要，因为冰可以强烈地影响云动力学、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式的理解非常重要。第三个目标是通过表征冰核化合物，并将其与已知的植物源冰核细菌的化合物进行比较，从而更好地了解海洋细菌冰核的分子基础，这是迄今为止唯一详细研究的冰核细菌。该活动将支持博士后研究人员开始学术生涯，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推广场所。

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.