Evolutionary dynamics and population genomics of cyanobacterial blooms

蓝藻水华出现在世界各地的湖泊中，几乎每年都会在魁北克的许多湖泊中发生。水华微生物群落的主要成员通常是蓝藻铜绿微囊藻，其中一些菌株会产生对人类和牲畜有害的毒素。因此，水华可能会对公众健康构成威胁，许多研究都在了解水华动态和毒素产生的生物学方面。我们知道，在被富含氮和磷的化肥污染的湖泊中，水华更严重，但我们仍然缺乏控制水华或预测它们是否有毒的能力。像许多微生物一样，微囊藻迅速(至少在夏季开花期间)增长到庞大的种群规模，产生能够对自然选择做出快速反应的遗传多样性种群--这意味着它们可以实时进化，年复一年，或在夏季开花期间进化。 该项目的目标是通过对魁北克湖自然种群的基因组进行测序，观察微囊藻在几个月甚至几年的时间里的进化。这将帮助我们回答基本问题：微囊藻种群是否重复遵循相同的进化轨迹，在每一次夏季开花期间，相同的菌株(或具有共同基因集的菌株)“获胜”？如果是这样的话，这意味着开花在原则上是可以预测的。这项研究还将确定为微囊藻提供选择优势的突变。如果有特定的有利突变或基因促进了水华的形成，这些基因的存在或缺失可能提供有价值的水华风险的“生物标志物”。这些基因的细胞功能可能被用来帮助防止水华。除了这些对加拿大公共和环境健康的实际成果外，这一研究项目还将提供一个难得的实时进化一瞥，增加我们对微生物如何适应自然环境的理解。在这项研究过程中，14名高素质人员将在多学科环境中接受培训，包括与加拿大和国际合作者一起进行计算和实验室工作。

Cyanobacterial blooms occur in lakes worldwide, and almost yearly in many Quebec lakes. The dominant member of the bloom's microbial community is typically the cyanobacterium Microcystis aeruginosa, some strains of which produce toxins harmful to humans and livestock. Blooms can therefore pose a public health threat, and much research has gone into understanding the biology of bloom dynamics and toxin production. We know that blooms are more severe in lakes polluted with nitrogen- and phosphorus-rich fertilizers, but we still lack the ability to control blooms or predict whether they will be toxic. Like many microbes, Microcystis grow rapidly (at least during summer blooms) to large population sizes, generating genetically diverse populations that can respond rapidly to natural selection - meaning that they can evolve in real time, from year to year, or over the course of a summer bloom. The goal of this project is to 'watch' Microcystis evolve over months and years by sequencing genomes from natural populations in Quebec lakes. This will help us answer fundamental questions: Do Microcystis populations follow the same evolutionary trajectory repeatedly, with the same strains (or those with a common set of genes) 'winning' during every summer bloom? If so, this means that blooms are predictable in principle. This research will also identify mutations that provide a selective advantage to Microcystis. If there are particular advantageous mutations or genes that promote bloom formation, the presence or absence of such genes could provide valuable 'biomarkers' of bloom risk. The cellular functions of these genes could potentially be targeted to help prevent blooms. In addition to these practical outcomes for public and environmental health in Canada, this research project will provide a rare glimpse into evolution in real time, adding to our understanding of how microbes adapt to their natural environments. Over the course of this research, 14 highly-qualified personnel will be trained in a multidisciplinary setting, involving computational and laboratory work with collaborators in Canada and internationally.