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。早期对南极海岸/大陆架/海洋生态系统和亚热带海洋生态系统这两个截然不同的栖息地的研究表明，微生物环的生态作用和浮游细菌的生理机能存在显著差异。这两个栖息地与陆源有机物的输入隔绝，因此为研究浮游植物来源的原生有机物的细菌代谢提供了极好的机会。浮游生物群落参数的强烈对比使这两个地点成为比较的理想地点。这项研究将嵌入到这两个地点（北太平洋的美国- jgofs夏威夷海洋时间序列和南极洲的帕尔默LTER）的正在进行的项目中，这些项目提供后勤支持和关于广泛的水文、化学和生物参数的支持数据，并提供大量的时空变化文件。初步的野外研究结果表明，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循环利用的调节，海水中罕见的有机物，特别是组氨酸，对细菌外酶的表达起着很大的调节作用。太阳紫外线辐射对溶解有机物的光解作用也在细菌外酶的调节中起作用。在生态上不同的微生物群落中对这些现象进行更深入的研究，将有助于理解浮游细菌与其他微生物群落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.