Degradation of Collidal Organic Matter in Seawater

为了更好地了解上层海洋的碳循环，我们研究了天然浮游细菌对海藻溶解弧菌制备的膜和可溶性蛋白质的降解，这些蛋白质被放射性标记为^ 3h或^<14>C亮氨酸。一阶动力学常数表明，粗膜提取物中蛋白质的降解速率明显低于可溶性蛋白质。确定与膜密切相关的蛋白质在两天内没有降解，而相当一部分可溶性蛋白质在同一时间内被降解。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。我们的数据支持大分子有机配合物在海水中溶解有机碳（DOC）的临时储存中起作用的假设。这一结果也与最近发现的细菌膜蛋白在海水中积累一致。海水中大量难熔DOC的形成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，二氧化碳是地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.