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

这项研究验证了一种假设，即在海水中，蛋白质被吸附在亚微米颗粒上的降解速度比同一蛋白质自由溶解的速度更慢。研究了溶解或吸附在聚苯乙烯乳珠(直径0.126~1.5um)上的甲基-~3H-牛血清白蛋白的细菌水解性。在BSA培养基上培养的混合菌群、两个细菌分离物和一个天然海洋细菌群对~3H-BSA的水解率(1/10~1；1/200)比游离~H-BSA的水解率慢得多。这些比较表明，水解率主要受~3H-BSA向细菌的转运速率的影响。两株细菌对吸附的~3H-BSA的水解率有很大差异，这可能是由于细菌蛋白酶对~3H-BSA的亲和力不同所致。这一研究结果支持了这样的假设，即吸附在亚微米颗粒上大大降低了蛋白质的降解速度，并表明溶解有机物(DOM)的吸附可能是一种机制，将不稳定的DOM暂时储存在一个缓慢降解的“半不稳定”池中，这使得它可以用于出口和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.