Microbial Community Structure and Expression of Functional Genes Involved in the Seasonal Cycling of DMSP in the Southern Ocean

南极洲附近的南大洋是一个以季节性驱动的海洋浮游植物大量繁殖为特征的区域，这些浮游植物通常以微藻种类为主，它们产生大量的二甲基磺酰丙酸盐（DMSP）。DMSP可以转化为化合物二甲基硫化物（DMS），这是一种可以逃逸到大气中的分子，在那里它具有很强的凝结特性，参与区域云的形成。DMSP的生产可以影响海水中微生物组合的多样性和组成，海水中微生物的类型和活动可能会影响DMSP\DMS的产量。该提案旨在研究DMSP在南极水域微生物群落结构中的作用，以及这种结构如何影响DMSP循环。该项目将利用南极研究向一系列受众（包括缅因州的高中生和本科生）介绍微生物多样性和生物地球化学相关的概念和数据。该项目还将吸引农村K-8学校的教师和学生，并将允许与一名科学作家和插画家合作，后者将加入该领域的团队。作者将利用南大洋的经历作为海报和一本书的背景，介绍拟议的研究和研究极端环境的科学家。该项目将研究(1)南部海域DMSP的循环对细菌和原生生物组合的组成和多样性的影响程度；(2)相反，南大洋原生生物和细菌组合的组成和多样性是否影响DMSP循环的幅度和速率；(3)海洋细菌对DMSP降解基因的季节性表达及对DMSP添加量的响应；并且，通过量化(4)DMSP生产者和DMSP消费者及其捕食者的存在所产生的微生物网络来综合这些结果，这些微生物网络都参与了南部海域DMSP的循环。工作将在夏季和秋季对不同微生物群落进行实地取样时，通过dmsp修饰的天然样品进行连续生长实验来完成。来自分子（如16S/ 18S标签序列，dmsp循环基因转录）和生物地球化学（如生物硫循环，细菌生产，微生物生物量）调查的数据将通过网络分析整合。

The Southern Ocean in the vicinity of Antarctica is a region characterized by seasonally-driven marine phytoplankton blooms that are often dominated by microalgal species which produce large amounts of dimethylsulfoniopropionate (DMSP). DMSP can be converted to the compound dimethylsulfide (DMS) which is a molecule that can escape into the atmosphere where it is known to have strong condensation properties that are involved in regional cloud formation. Production of DMSP can influence the diversity and composition of microbial assemblages in seawater and the types and activities of microbes in the seawater will likely affect the magnitude of DMSP\DMS production. The proposal aims to examine the role of DMSP in structuring the microbial communities in Antarctic waters and how this structuring may influence DMSP cycling. The project will leverage the Antarctic research to introduce concepts and data linking microbial diversity and biogeochemistry to a range of audiences (including high school and undergraduate students in Maine). The project will also engage teacher and students in rural K-8 schools and will allow a collaboration with a science writer and illustrator who will join the team in the field. The writer will use the southern ocean experience as the setting for a poster and a book about the proposed research and the scientists studying extreme environments. The project will examine (1) the extent to which the cycling of DMSP in southern ocean waters influences the composition and diversity of bacterial and protistan assemblages; (2) conversely, whether the composition and diversity of southern ocean protistan and bacterial assemblages influence the magnitude and rates of DMSP cycling; (3) the expression of DMSP degradation genes by marine bacteria seasonally and in response to additions of DMSP; and, to synthesize these results by quantifying (4) the microbial networks resulting from the presence of DMSP-producers and DMSP-consumers along with their predators, all involved in the cycling of DMSP in southern ocean waters. The work will be accomplished by conducting continuous growth experiments with DMSP-amended natural samples during field sampling of different microbial communities present in summer and fall. Data from the molecular (such as 16S/ 18S tag sequences, DMSP-cycle gene transcripts) and biogeochemical (such as biogenic sulfur cycling, bacterial production, microbial biomass) investigations will be integrated via network analysis.