Studies of Inorganic Nutrient Limitation in Planktonic Bacteria

浮游细菌的生长通常被认为受到有机碳底物耗尽的限制。与这一假设相反，过去几年对科罗拉多州湖泊中自然浮游细菌种群的实验表明，这些湖泊中细菌的生长往往受到磷的限制。这项提议概述了一项计划，以检验浮游植物比细菌拥有更大的磷存储能力的假设，这在某些条件下抵消了细菌的动力学优势。实验将记录(1)营养充足和营养不足条件下细菌的磷库存，(2)细菌通过无机和天然有机磷部分以及通过共生浮游植物组合对磷的吸收速率，以及(3)混合群落中细菌和浮游植物对磷的利用，其中有机磷是唯一的磷源，或无机磷以脉冲形式供应，这可能是通过自然界中的营养物质斑块发生的。这三组实验的综合结果将证明磷存储容量对细菌和浮游植物之间的磷竞争结果的影响。

The growth of planktonic bacteria is generally assumed to be limited by depletion of organic carbon substrate. In contrast to this assumption, experimental work with natural bacterioplankton populations in Colorado lakes over the past several years show that growth of bacteria in these lakes is frequently limited by phosphorus. This proposal outlines a plan for testing the hypothesis that phytoplankton possess greater phosphorus storage capacity than bacteria, which offsets the kinetic superiority of bacteria under some conditions. Experiments will document (1) the phosphorus inventory of bacteria under nutrient-sufficient and nutrient-deficient conditions, (2) the uptake rate of phosphorus through both inorganic and natural organic phosphorus fractions by bacteria and by co-occurring phytoplankton assemblages, and (3) the phosphorus usage of bacteria and phytoplankton components in mixed communities for which organic phosphorus is the only phosphorus source, or for which inorganic phosphorus is supplied in a pulse, as might occur through nutrient patchiness in nature. The combined outcome of these three sets of experiments will demonstrate the influence of phosphorus storage capacity on the outcome of phosphorus competition between bacteria and phytoplankton.