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

在拟议的研究中，我的目标是对淡水湖(也称为雪湖)中宏观有机集合体的微生物降解进行时间研究。我将使用我们最近开发的流动滚动水箱在接近现场的条件下研究雪湖。我的目标是确定微生物在下沉/降解颗粒物上演替的因素，同时解释单个颗粒物在群落组成和活动方面的异质性。雪湖是水生颗粒物有机质的重要组成部分，由不同来源的颗粒物(如浮游植物细胞、浮游动物身体和异地有机质)组成。斯诺湖有机和无机分子的浓度往往比本底水平高出2-4个数量级，为相关微生物提供了强大的能量、碳和营养来源。因此，这些颗粒被异养菌大量定居，这些异养菌在它们的降解过程中发挥着至关重要的作用。这些细菌的群落结构在不同的颗粒之间是不同的，但这一观察背后的驱动力尚未被研究。颗粒上的微生物群落会随时间发生变化，这一演替过程归因于碳质的变化；然而，我的初步结果显示，相关微生物基因的表达在至少8天内没有变化。因此，我假设，形成与颗粒相关的群落的主要力量是生物之间的相互作用。这些包括细菌-真核细菌、细菌-细菌和细菌-病毒的相互作用。为了评估雪湖在自然条件下的命运，以及更好地理解决定相关微生物群落在空间和时间上的性质的过程，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的颗粒之间微生物活动的异质性；C)与碳质变化比较，评估生物间相互作用对雪湖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，使用新的流动滚动槽系统，结合群落指纹、活性测量、转录和有机物表征。这项研究的结果将在微观尺度上提供关于微生物机制的关键知识，以更好地了解水生系统在有机质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.