Microbial transformation of DOC in the ocean

海洋中 DOC 的微生物转化

• 批准号: 06044066
• 负责人: KOGURE Kazuhiro
• 金额: $ 5.95万
• 依托单位: Ocean Research Institute, University of Tokyo
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for international Scientific Research
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-06044066/
• 关键词: Dissolved Organic Matter; Marine Bacteria; Degradation; Submicron Particles; 分解実験; 高分子有機物

Recent studies have discovered the occurrence of numerous submicron particles in natural seawater. The numbers exceed those of bacteria by at least an order of magnitude in the surface layrs of marine environments. The understanding of their origin and fate are becoming an important issue to clarify the transformation or cycles of organic matter, including semi-labile fractions. At present, however, their degradation process is poorly understood. In this work, we tested a hypothesis that the protein associated with membraneous submicron particles is less easily degraded than those in dissolved state. Model substrates were prepared and their degradation rates by natural microbial assemblages were followed.Membrane fraction which was labeled with ^3H and soluble fractions labeled with ^<14>C were prepared from a marine bacterium, Vibrio alginolyticus (138-2). In addition, we joined two cruises in Delaware Bay in summer, 1995 to clarify the population size and activity of bacteria in this particular environments. The results showed that the degradation rates of protein in membrane fraction was much slower than in the soluble fraction ; sometimes less than one third of the latter. This indicates that the association with other molecules such as lipids or polysaccharides makes the biopolymer less degradable or less accessible by bacterial attack. The result has a great implication to understand the fate of semi-labile organic matter in marine environment. The field date from the cruises are now being analyzed and will be discussed with the degradation experimental results stated above.

最近的研究发现天然海水中存在大量亚微米颗粒。这些数量超过海洋环境表层细菌的数量至少一个数量级。了解它们的起源和命运正在成为澄清有机物（包括半不稳定部分）转化或循环的一个重要问题。然而目前，人们对它们的降解过程知之甚少。在这项工作中，我们测试了一个假设，即与膜亚微米颗粒相关的蛋白质比溶解状态的蛋白质更不易降解。制备模型底物并跟踪其通过天然微生物组合的降解率。从海洋细菌溶藻弧菌(Vibrio alginolyticus)(138-2)制备用^ 3 H标记的膜级分和用^ 14 C标记的可溶性级分。此外，我们于 1995 年夏天参加了特拉华湾的两次航行，以查明该特定环境中细菌的种群规模和活动。结果表明，膜组分中蛋白质的降解速度比可溶组分中的蛋白质降解速度慢得多；有时还不到后者的三分之一。这表明与其他分子（例如脂质或多糖）的结合使生物聚合物不易降解或不易受到细菌攻击。该结果对于了解海洋环境中半不稳定有机物的归宿具有重要意义。目前正在分析巡航的现场数据，并将与上述降解实验结果进行讨论。