Degradation of Collidal Organic Matter in Seawater

为了更好地了解海洋上层的碳循环，我们研究了天然浮游细菌对溶藻弧菌（Vibrio alginolyticus）的膜蛋白和可溶性蛋白的降解作用。溶藻弧菌用^3 H-或^3 <14>C-亮氨酸进行了放射性标记。一级动力学常数表明，蛋白质在粗膜提取物的降解速度显着低于可溶性蛋白质。确定与膜密切相关的蛋白质在两天内没有降解，而在同一时期内降解了相当大一部分可溶性蛋白质。这些数据与膜和细胞壁材料严重限制细菌蛋白酶进入膜蛋白的模型一致。我们的数据支持的假设，大分子有机复合物发挥作用，在临时存储溶解有机碳（DOC）在海水中。该结果也与最近发现的细菌膜蛋白在海水中积累一致。在海水中形成一个大的难降解DOC池可能会影响海洋中的碳循环和大气中二氧化碳浓度的变化，二氧化碳是我们星球上最重要的温室气体。

In order to better understand the carbon cycle in the upper oceans, we examined degradation by natural bacterioplankton of membrane and soluble proteins prepared from the marine bacterium, Vibrio alginolyticus, radiolabeled with ^3H-or ^<14>C leucine. First order kinetic constants indicated that proteins in crude mambrane extract are degraded at significantly slower rates than the soluble proteins. Proteins determined to be intimately associated with the membrane were not degraded over two days, while a substantial fraction of soluble proteins was degraded during the same period. The data are consistent with a model that membrane and cell wall materials severely restrict access of bacterial proteases to membrane proteins. Our data support the hypothesis that macromolecular organic complexes play a role in temporary storage of dissolved organic carbon (DOC) in seawater. The results are also consistent with recent finding that bacterial membrane protein accumulates in seawater. The formation of a large pool of refractory DOC in seawater may influence carbon cycling in the ocean and changes in atmospheric concentrations of carbon dioxide, the most important greenhouse gas on our planet.