Fitting Mixotrophy into the Microbial Loop Paradigm: Advantages and Consequences of Mixotrophic Behavior Among Phagotrophic Algae

9508571 Caron混合营养是在单一生物体中异养和光养营养的组合。在单细胞微藻中，各种各样的物种摄取颗粒有机物质。几种可能的适应优势存在的兼养行为之间的吞噬藻类。到目前为止，摄食行为有三种一般策略：（1）在高细菌丰度下的主要食养生长，其中当细菌以低丰度存在时，光养用作非常缓慢生长的机制，（2）主要光养生长，其中食养用作在低光强度下补充生长的机制，和（3）以光养为主的生长，其中吞噬作为获取主要营养物如氮或磷的机制。 这项研究将集中在吞噬微藻与纯光合原生生物（藻类）和纯异养原生生物（原生动物）竞争的能力。该框架包括一个模型，将mixotrophy到一个简单的微生物食物网，以产生有关的吞噬藻类与nonphagotrophic藻类和原生动物竞争的能力的假设。该模型是基于对混合营养行为的三种策略的理解。在实验室中，将通过连续培养的藻类、原生动物和噬菌体藻类之间的一系列竞争实验来检验假设。实验将研究光的限制，增加不稳定的溶解有机碳，和无机营养限制的吞噬藻类与nonphagotrophic藻类和原生动物竞争的生长的影响。指导性假设是，不同种类的食藻所表现出的不同行为为它们提供了竞争优势，这将导致它们在特定环境下的成功。这些实验将建立这些情况，并为解释自然界中混合营养物种的分布提供有价值的见解。

9508571 Caron Mixotrophy is the combination of heterotrophic and phototrophic nutrition in a single organism. Among the unicellular microalgae, a wide variety of species ingest particulate organic material. Several possible adaptive advantages exist for mixotrophic behavior among phagotrophic algae. Thus far, three general strategies are served by phagotrophic behavior: (1) primarily phagotrophic growth at high bacterial abundances, with phototrophy serving as a mechanism for very slow grouth when bacteria are present at low abundances, (2) primarily phototrophic growth with phagotrophy serving as a mechanism for supplementing growth at low light intensities, and (3) primarily phototrophic growth with phagotrophy serving as a mechanism for acquiring major nutrients such as nitrogen or phosphorus. This research will focus on the ability of phagotrophic microalgae to compete with purely phototrophic protists (algae) and purely heterotrophic protists (protozoa). The framework includes a model that incorporates mixotrophy into a simple microbial food web in order to generate hypotheses concerning the ability of phagotrophic algae to compete with nonphagotrophic algae and protozoa. The model is based on the understanding of the three strategies for mixotrophic behavior. Hypotheses will be tested in the laboratory via a series of competition experiments between algae, protozoa, and phagotrophic algae in continuous cultures. Experiments will examine the effects of light limitation, additions of labile dissolved organic carbon, and inorganic nutrient limitation on the growth of phagotrophic algae competing with nonphagotrophic algae and protozoa. The guiding hypothesis is that the different behaviors exhibited by different species of phagotrophic algae provide them with a competitive advantage that will result in their success under particular circumstances. These experiments will establish those circumstances and provide valuable insights for explaining the distribution of mixotrophic species in na ture.