Collaborative Research: Role of Nutrient Limitation and Viral Interactions on Antarctic Microbial Community Assembly: A Cryoconite Microcosm Study

冰孔是冰川表面充满沉积物的融化孔，在其他大部分冰冻和贫瘠的景观中，它可能是活跃微生物生命的重要场所。先前在南极洲麦克默多干谷的研究表明，微生物的病毒感染和肥料（即营养物质）的普遍缺乏可能是影响低温孔中微生物群落发育和功能的重要因素。研究人员提出了一种实验方法来了解营养限制如何影响微生物的多样性（物种数量）和总体丰度，以及微生物的多样性和丰度如何反过来影响寄生在低温沉积物中微生物的病毒的多样性、丰度和感染类型。研究人员将使用以前从南极冰川收集的沉积物，这些沉积物含有不同浓度的病毒和营养物质，以建立一个营养物质添加实验，以确定营养物质如何影响微生物和病毒种群动态。这些结果将加深我们对微生物群落一般是如何被营养物质和病毒塑造的理解，并为病毒在极冷环境中的功能提供新的见解。研究人员将在科学期刊上发表他们的发现，并与针头研究所合作，与来自农村学校的K-12学生分享他们的发现，并将通过参与该大学的科学、技术、工程和数学路线提升研究计划，将来自少数民族的本科生与极地研究联系起来。外联活动将通过专业科学传播者制作和分发的视频来实现。该研究通过利用南极地区的独特特征作为科学观测平台，推进了美国国家科学基金会的目标，即扩大对南极系统、生物群和过程的基础知识。主要研究人员提出了一种实验方法，以了解营养限制如何影响微生物多样性和丰度，以及它们对南极冰芯孔中病毒多样性、丰度和感染模式（裂解vs溶原性）的级联效应。低温孔是理想的自然微观环境，可用于操作研究，这在其他冰冻圈生态系统中是不可用的。pi将使用先前从病毒多样性和营养水平梯度中收集的冰凝石来解决冰凝石沉积物中关键限制性营养物质和微生物-病毒群落动态的问题。营养操纵实验将在一个与原位冰凝石洞的光照和温度状况非常接近的生长室内进行，以验证三个核心假设：(1)磷的有效性限制了冰凝石洞中微生物的生产力和丰度；(2)降低低多样性冰川中冰凝石的营养限制将增加物种多样性，导致微生物群落与营养丰富的冰川相似；(3)放宽营养限制将增加适宜宿主的可得性，从而增加病毒的多样性和丰度，降低溶原性感染的发生率。通过在现实范围内控制营养限制，该项目将有助于验证南极冰凝石孔中假设的磷限制，并将更广泛地扩展对冰冻圈中营养物质、多样性和病毒感染动态之间联系的理解。更好地了解冰凝石沉积物中的这些动态可以提高科学家预测冰冻圈环境变化未来影响的能力。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Cryoconite holes are sediment-filled melt holes in the surface of glaciers that can be important sites of active microbial life in an otherwise mostly frozen and barren landscape. Previous studies in the McMurdo Dry Valleys, Antarctica suggest that viral infections of microbes, and a general lack of fertilizers (i.e., nutrients), may be important factors shaping the development and functioning of microbial communities in cryoconite holes. The researchers propose an experimental approach to understand how nutrient limitation affects diversity (number of species) and overall abundance of microbes, and how the diversity and abundance of microbes in turn affects the diversity, abundance, and infection type of viruses that parasitize the microbes in cryoconite sediments. The researchers will use sediments previously collected from Antarctic glaciers that have varying concentrations of viruses and nutrients, to set up a nutrient-addition experiment to determine how nutrients affect microbial and viral population dynamics. The results will deepen our understanding of how microbial communities in general are shaped by nutrients and viruses and give new insights into the functioning of viruses in extremely cold environments. The researchers will publish their findings in scientific journals and will share their discoveries with K-12 students from rural schools in collaboration with the Pinhead Institute and will connect undergraduate students from under-represented minorities to polar research through participation in the university’s Science, Technology, Engineering & Mathematics Routes Uplift Research Program. Outreach will be achieved through videos produced and distributed by a professional science communicator. The research advances a National Science Foundation goal of expanding fundamental knowledge of Antarctic systems, biota, and processes by utilizing the unique characteristics of the Antarctic region as a science observing platform. The Principal Investigators propose an experimental approach to understand how nutrient limitation affects microbial diversity and abundances and their cascading effects on virus diversity, abundance, and mode of infection (lysis vs. lysogeny) in Antarctic cryoconite holes. Cryoconite holes are ideal natural microcosms for manipulative studies, not available in other cryospheric ecosystems. The PIs will use previously collected cryoconite from across a gradient of both viral diversity and nutrient levels to address questions about key limiting nutrients and microbial-viral community dynamics in cryoconite sediments. Nutrient manipulation experiments will be conducted in a growth chamber that closely approximates the light and temperature regime of in situ cryoconite holes to test three core hypotheses: (1) phosphorus availability limits microbial productivity and abundance in cryoconite holes; (2) relaxing nutrient limitation in cryoconite from low-diversity glaciers will increase species diversity, leading microbial communities to resemble those found on more nutrient-rich glaciers; (3) relaxing nutrient limitation will increase the diversity and abundance of viruses by increasing the availability of suitable hosts, and decrease the prevalence of lysogenic infections. By manipulating nutrient limitation within a realistic range, this project will help verify hypothesized phosphorus limitation of Antarctic cryoconite holes and will extend understanding of the connections between nutrients, diversity, and viral infection dynamics in the cryosphere more generally. A better understanding of these dynamics in cryoconite sediments improves the ability of scientists to forecast future impacts of environmental changes in the cryosphere.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.