ABSTRACT: In the phosphate-depleted oligotrophic ocean, microbes utilize various dissolved organic phosphorus (P) compounds as alternative P sources, using enzymes such as alkaline phosphatases. However, knowledge of such P acquisition mechanisms is limited, especially in association with the physiology of nitrogen-fixing organisms, which play a substantial role in marine biogeochemical cycling. We show that nonaxenic clonal cultures of 2 oceanic diazotrophs, Trichodesmium erythraeum and Crocosphaera watsonii, have the ability to utilize phosphate diester as their sole P source, using a model artificial compound—bis- p-nitrophenyl phosphate (bisNPP). Although both diazotroph cultures likely preferred phosphate monoester to diester, the expressed diesterase activity was theoretically sufficient to fulfill their P demands, and they showed significant growth in bisNPP-added media. Interestingly, a distinct difference in their growth trends was observed, with faster onset of growth by C. watsonii and delayed onset of growth by T. erythraeum. This indicates that the C. watsonii consortium can effectively and rapidly assimilate in situ diesters as alternative P sources in the field. Nonetheless, when considering the poor bisNPP utilization reported from other marine phytoplankton taxa, our results indicate that the utilization of particular diester compounds is a notable and advantageous strategy for both diazotroph consortia to alleviate P limitation in the oligotrophic ocean.

中文翻译：

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海洋重氮菌Trichodesmium erythraeum和Crocosphaera watsonii对磷酸二酯的利用

摘要：在贫磷酸盐的贫营养海洋中，微生物利用各种酶（例如碱性磷酸酶）利用各种溶解的有机磷（P）化合物作为替代的磷源。但是，对这种磷获取机制的了解是有限的，特别是与固氮生物的生理学有关，固氮生物在海洋生物地球化学循环中起着重要作用。我们表明，使用模型人工化合物-bis - p，2个海洋重氮营养生物，红毛Trichodesmium erythraeum和Crocosphaera watsonii的非轴生克隆培养物具有利用磷酸二酯作为其唯一P源的能力。磷酸硝基苯酯（bisNPP）。虽然两种重氮营养菌培养物都可能更倾向于磷酸单酯而不是二酯，但理论上表达的二酯酶活性足以满足其对磷的需求，并且在添加bisNPP的培养基中它们均显示出显着的增长。有趣的是，在他们的增长趋势明显的差异，观察到，与起效更快由生长的C. watsonii和发病生长延迟T.藻。这表明华氏梭菌财团可以有效，迅速地原位吸收二酯作为该领域的替代P源。但是，考虑到其他海洋浮游生物类群报告的bisNPP利用率不佳时，我们的结果表明，利用特定的二酯化合物是重氮营养族联合体减轻贫营养性海洋中P限度的重要且有利的策略。