Microbial metabolic processes that control the dynamics of high-molecular-weight dissolved organic matter in the ocean

这项研究验证了一个假设，即在海水中被亚微米颗粒吸附的蛋白质比自由溶解的蛋白质降解得更慢。研究了甲基-^ 3h -牛血清白蛋白（^3H-BSA）溶解或吸附到颗粒（聚苯乙烯乳胶珠，直径0.126-1.5 μ m）上的细菌水解。在BSA培养基上培养的混合细菌组合，两种细菌分离物和天然海洋细菌组合水解吸附^3H-BSA的速度比自由3H-BSA慢得多（1/10-<1/200）。测定的水解率与预测的细菌与自由溶解或吸附在不同直径微球上的^3H-BSA的碰撞概率进行了比较。这些比较表明，水解速率主要受^3H-BSA向细菌的转运速率的影响。两种细菌菌株对^3H-BSA的水解作用差异很大，这似乎可以用细菌蛋白酶对^3H-BSA的亲和力差异来解释。本研究的结果支持了亚微米颗粒吸附大大降低蛋白质降解速率的假设，并表明溶解有机物（DOM）的吸附可能是一种机制，可以暂时将不稳定的DOM储存在缓慢降解的“半不稳定”池中，使其可供出口并通过地球化学过程进一步修饰。

This study tested the hypothesis that protein adsorbed to submicron particles in seawater is more slowly degraded than the same protein freely dissolved. Bacterial hydrolysis of methyl-^3H-bovine serum albumin (^3H-BSA) dissolved or adsorbed to particles (polystirene latex beads, diameters 0.126-1.5mum) was examined. Mixed bacterial assemblages cultured on BSA media, two bacterial isolates, and a natural marine bacterial assemblage hydrolyzed adsorbed ^3H-BSA at much slower rates (1/10-<1/200) than free 3H-BSA.The measured hydrolysis rates were compared with the predicted collision probabilities between bacteira and ^3H-BSA freely dissolved or adsorbed to beads of different diameters. These comparisons suggest that the hydrolysis rate is influenced primarily by the transport rate of ^3H-BSA to bacteria. Hydrolysis of adsorbed ^3H-BSA differed greatly between two bactirial strains, which appears to be explained by differences in the affinity of bacterial proteases to ^3H-BSA.The results of this study support the hypothesis that adsorption onto submicron particles greatly reduces degradation rate of proteins and suggest that the adsorption of dissolved organic matter (DOM) may be a mechanism that temporarily stores labile DOM in a slowly-degrading, "semi-labile" pool, which makes it available for export and further modification by geochemical processes.