Determinants of Community Structure, Function and Succession of Freshwater Microorganisms Colonizing Lake Snow

在我提出的研究中，我的目标是对淡水湖（也称为雪湖）宏观有机聚集体的微生物降解进行时间研究。我将在接近原位的条件下使用我们最近开发的一个流过的滚动水箱来研究雪湖。我的目的是确定负责微生物演替的下沉/降解颗粒的因素，同时考虑到单颗粒在群落组成和活性上的异质性。雪湖是水体颗粒有机质的重要组成部分，由不同来源的颗粒组成（如浮游植物细胞、浮游动物尸体和外来有机物）。雪湖上有机和无机分子的浓度经常超过背景水平2-4个数量级，为相关微生物提供了强有力的能量、碳和营养来源。结果，这些颗粒被异养细菌大量定植，这些细菌在它们的降解中起着至关重要的作用。这些细菌的群落结构在单个颗粒之间是不同的，但这种观察背后的驱动力尚未得到研究。颗粒上微生物群落随时间变化，演替过程归因于碳质变化；然而，我的初步结果显示，至少在8天内，相关微生物基因的表达没有变化。因此，我假设形成粒子相关群落的主要力量是生物间的相互作用。这些包括细菌-真核生物，细菌-细菌和细菌-病毒的相互作用。为了评估湖雪在自然条件下的命运，以及更好地了解相关微生物群落在空间和时间上的性质，我计划：a)确定颗粒源对微生物定植异质性的影响；B)确定相同来源和不同来源颗粒之间微生物活性的异质性；C)与碳质量的变化相比，评估生物间相互作用对雪湖定植微生物群落演替事件的贡献。为了解决所有问题，我将研究多个实验室制造的单个颗粒，使用新型的流过滚动罐系统，结合社区指纹识别、活性测量、转录组学和有机物表征。本研究的结果将在微观尺度上提供微生物机制的关键知识，以更好地理解水生系统在有机物循环和储存中的作用。

In the proposed research, I aim to conduct a temporal study on the microbial degradation of macroscopic organic aggregates in freshwater lakes, also known as Lake Snow. I will study Lake Snow at near-in-situ conditions using a flow-through rolling tank we have recently developed. I aim to determine the factors responsible for microbial succession on sinking / degrading particles while accounting for single particle heterogeneity both in community composition as well as in activity. Lake Snow makes up a significant portion of the aquatic particulate organic matter and consists of different source particles (e.g. phytoplankton cells, zooplankton-carcasses and allochthonous organic matter). Concentrations of organic and inorganic molecules, on Lake Snow, often exceed background levels by 2-4 orders of magnitude providing associated microorganisms with a potent energy, carbon and nutrient source. As a result, these particles are heavily colonized by heterotrophic bacteria that play an essential role in their degradation. The community structure of these bacteria differs between individual particles, but yet the driving force behind this observation has not been studied. The microbial community on particles changes in time, a succession process attributed to changes in carbon quality; my preliminary results, however, show no changes in expression of related microbial genes over at least 8 days. Therefore, I hypothesize that a major force in shaping the particle-associated community is inter-organisms interactions. These include Bacteria-Eukarya, Bacteria-Bacteria and Bacteria-Viruses interactions. To evaluate the fate of Lake Snow under natural conditions as well as to achieve a better understanding of the processes determining the nature of the associated microbial community in space and time, I plan to: A) Determine the effects of particle sources on microbial colonization heterogeneity; B) Determine the heterogeneity in microbial activity among particles of the same and different source; C) Assess the contribution of inter-organisms interactions to succession events of Lake Snow colonizing microbial communities in comparison to changes in carbon quality. To address all topics, I will study multiple, lab-made, individual particles using novel flow-through rolling tank systems coupled with community fingerprinting, activity measurements, transcriptomics and organic matter characterization. The results of this study will provide crucial knowledge on microbial mechanisms at the microscale to better understand the role of aquatic systems in organic matter cycling and storage.