The impact of mixotrophic bacterivory on microbial food webs in changing lake ecosystems (LakeMix)

兼养原生生物是将光合作用与吞噬作用结合在一起的联合收割机，在海洋和淡水生态系统中很常见。然而，它们在食物网动态，包括营养相互作用中的作用还没有得到很好的理解。从海洋环境中积累的证据支持相当数量的重要性，混合营养作为细菌。然而，远洋食物网的模型仍然在很大程度上依赖于传统的二分法的自养和异养protists.In湖泊，mixotrophic bacteriovory很少被量化，虽然puericum mixotrophic类群的数量丰富，这些类群如何影响细菌群落的知识有限。虽然这似乎是显而易见的，光必须发挥关键作用的潜在重要性的混合营养，实验证据上的光对微生物食物网的影响是稀缺的，虽然光制度预计会改变的结果，例如，改变分层模式，由于全球变暖。在LakeMix中，我们的目标是通过评估气候相关变化背景下湖泊中混合营养噬菌体的定量和定性影响来填补这些空白。该项目围绕四个主要任务组织：（1）我们将对代表性的异养和混合营养类群进行实验室实验，以解决竞争性相互作用和选择性摄食，包括可变光照条件下它们对细菌群落的影响。(2)一个贫营养湖泊的自然群落的围隔实验将有助于测试混合营养的相对影响如何取决于光强度的背景下，由于气候变化改变湖泊分层。(3)在区域湖泊调查中，我们将确定相关的兼养食细菌沿着营养梯度。(4)一个欧洲规模的湖泊调查，涵盖了大的地理和环境梯度将进行评估的分布普遍mixotrophic taxa.Our多学科的项目相结合的控制实验在恒化器和围隔生态系统与全面的实地观察，从而跨越几个尺度的生态复杂性。独特的大型围隔生态系统设施IGB LakeLab将以新颖和创新的方式用于模拟不同的分层模式。最先进的分子方法和应用，包括高通量测序技术与稳定同位素探测和流式细胞术相结合，将用于确定重要的兼养类群，并表征其对细菌群落的影响。该项目将产生关键的定量数据，这些数据是将混合营养作为微生物食物网和湖泊生态系统模型中的关键功能性状所需的，并揭示了这一普遍但难以捉摸的功能群的生态学。

Mixotrophic protists, that combine photosynthesis with phagotrophy, are common in marine and freshwater ecosystems. Yet their role in food web dynamics, including trophic interactions, is not well understood. Accumulating evidence from marine environments supports considerable quantitative importance of mixotrophs as bacterivores. Nevertheless, models of the pelagic food web still largely rely on the traditional dichotomy of autotrophic and heterotrophic protists.In lakes, mixotrophic bacterivory has rarely been quantified, and although putatively mixotrophic taxa are numerically abundant there is limited knowledge on how these taxa impact bacterial communities. While it seems obvious that light must play a pivotal role for the potential importance of mixotrophy, experimental evidence on the effect of light on microbial food webs is scarce although light regimes are predicted to change as a result of, for example, altered stratification patterns due to global warming. In LakeMix, we aim to fill these voids by assessing the quantitative and qualitative impact of mixotrophic bacterivory in lakes in the context of climate-related changes.The project is organized around four major tasks: (1) We will perform laboratory experiments with representative heterotrophic and mixotrophic taxa to address competitive interactions and selective feeding, including their impact on bacterial communities under variable light conditions. (2) Mesocosm experiments with natural communities of an oligotrophic lake will serve to test how the relative impact of mixotrophy depends on light intensity in the context of altered lake stratification due to climate change. (3) In a regional lake survey, we will identify the relevant mixotrophic bacterivores along a trophic gradient. (4) A European-scale lake survey that covers large geographical and environmental gradients will be carried out to assess the distribution of prevalent mixotrophic taxa.Our multidisciplinary project combines controlled experimentation in chemostats and mesocosms with comprehensive field observations, thereby spanning several scales of ecological complexity. The unique large-scale mesocosm facility, the IGB LakeLab, will be used in a novel and innovative way to simulate different stratification patterns. State-of-the-art molecular methods and applications, including high-throughput sequencing technology in combination with stable isotope probing and flow cytometry will be used to identify important mixotrophic taxa, and to characterize their impact on bacterial communities. This project will generate crucial quantitative data that is required for incorporating mixotrophy as a key functional trait in microbial food webs and models of lake ecosystems, and shed light on the ecology of this prevalent yet elusive functional group.