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

冰锥岩洞是冰川表面充满沉积物的融化洞，在原本大多冻结和贫瘠的土地上，这些洞可能是活跃微生物生命的重要场所。以前在南极洲麦克默多干燥山谷的研究表明，微生物的病毒感染以及普遍缺乏化肥(即营养)，可能是影响低温球果洞穴中微生物群落发展和功能的重要因素。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反过来又如何影响寄生在冷锥体沉积物中微生物的病毒的多样性、丰度和感染类型。研究人员将使用之前从南极冰川收集的沉积物，这些冰川含有不同浓度的病毒和营养物质，以建立一个营养添加实验，以确定营养物质如何影响微生物和病毒种群的动态。这些结果将加深我们对微生物群落一般是如何由营养物质和病毒塑造的理解，并为病毒在极端寒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Pinhead研究所合作，与农村学校的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，将来自未被充分代表的少数民族的本科生与极地研究联系起来。将通过由专业科学传播者制作和分发的视频进行宣传。这项研究提出了国家科学基金会的目标，即通过利用南极地区作为科学观测平台的独特特征，扩大关于南极系统、生物群和过程的基础知识。首席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，以及它们对南极低温球洞中病毒多样性、丰度和感染模式(裂解与溶源)的级联影响。对于操纵性研究来说，低温球体洞穴是理想的自然微观世界，这在其他冰冻圈生态系统中是不存在的。PIS将使用以前从病毒多样性和营养水平的梯度收集的冰锥，以解决有关冰锥沉积物中关键限制营养物质和微生物-病毒群落动态的问题。营养操纵实验将在一个与原地低温球洞的光温条件非常接近的生长室中进行，以检验三个核心假设：(1)磷的有效性限制了低温球洞中的微生物生产力和丰度；(2)放宽低多样性冰川的营养限制将增加物种多样性，导致微生物群落与营养更丰富的冰川上的微生物群落相似；(3)放松营养限制将通过增加合适宿主的可用性来增加病毒的多样性和丰度，并降低溶原性感染的流行。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低温球洞的磷限制假说，并将扩大对营养、多样性和更广泛的冰冻圈病毒感染动态之间的联系的理解。更好地了解冷冻石沉积物中的这些动力学，提高了科学家预测未来冰冻圈环境变化影响的能力。这一奖项反映了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。

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.