Cross-Site: Microbial Loop Dynamics and Regulation of Bacterial Physiology in Subtropical and Polar Marine Habitats

微生物环已被证明在所有气候带的海洋和淡水浮游生物生态系统中发挥重要作用。早期的研究在两个截然不同的栖息地：南极海岸/大陆架/海洋生态系统和亚热带海洋生态系统，微生物循环的生态作用和浮游细菌的生理表现出显着的差异。这两个栖息地是孤立的输入terrestrially来源的有机物，因此提供了很好的机会，研究细菌代谢的原生浮游植物来源的有机物。浮游生物群落参数的强烈对比使这两个网站的理想比较。这项研究将纳入这两个地点（北太平洋的美国-联合全球海洋观测系统夏威夷海洋时间序列和南极洲的帕尔默长期接触试验）正在进行的方案中，这些方案提供后勤支助和关于广泛的水文、化学和生物参数的支助数据，并广泛记录空间和时间变化。初步的现场结果表明，这两个地区的细菌群落在生理上是不同的，细菌生理受微生物群落结构的调节，特别是受食草动物对氮的再循环的调节，海水中罕见的有机化合物，特别是组氨酸，在调节细菌胞外酶表达方面发挥着重要作用，太阳紫外线对溶解有机物的光解作用也对细菌胞外酶的调节起作用。对生态学上不同的微生物群落中的这些现象进行更彻底的调查，将有助于理解浮游细菌与微生物群落其他部分之间复杂的相互作用。

The microbial loop has been shown to play an important role in marine and freshwater plankton ecosystems in all climatic zones. Earlier research in two contrasting habitats: an Antarctic coastal/ shelf/oceanic ecosystem and a subtropical oceanic ecosystem, have shown significant differences in the ecological role of the microbial loop and the physiology of bacterioplankton. These two habitats are isolated from input of terrestrially derived organic matter and so provide excellent opportunities to study bacterial metabolism of autochthonous organic matter of phytoplankton origin. Strong contrasts in plankton community parameters make these two sites ideal for this comparison. This study will be embedded within on-going programs at each of these two sites (US-JGOFS Hawaii Ocean Time-series in the North Pacific and Palmer LTER in Antarctica) that provide both logistical support and supporting data on a wide range of hydrographic, chemical and biological parameters, with extensive documentation of spatial and temporal variation. Preliminary field results show that bacterial communities in th ese two areas are physiologically distinct, that bacterial physiology is regulated by the structure of the microbial community and particularly by grazer recycling of nitrogen, that organic compounds rare in seawater, especially histidine, play a large role in regulation of bacterial ectoenzyme expression, and that photolysis of dissolved organic matter by solar ultraviolet radiation also plays a role in regulation of bacterial ectoenzymes. More thorough investigation of these phenomena in ecologically distinct microbial communities will facilitate understanding of the complex interactions between bacterioplankton and the rest of the microbial community.