URoL:EN: Understanding the rule of life facilitating the proliferation of toxic cyanobacterial benthic mats in flowing freshwaters

河流和小溪只占地球表面可用淡水总量的不到1%，但却具有巨大的生态和社会意义。最近，形成有毒蓝藻的生物膜，通常被称为底栖有害蓝藻华，已经在许多河流和溪流中广泛存在。这些蓝藻产生毒素作为次级代谢物，当食用时对人类和其他动物有害。来自底栖蓝藻属Microcoleus（以前的Phormidium）的物种可以在流动的淡水中形成厚垫，产生具有挑战性的空间和时间模式的蓝藻毒素。微藻底栖垫已经变得广泛，并表现出有趣的涌现行为。有毒菌株的微藻共存与它的无毒对应物和其他蓝藻。许多有毒的微藻物种的代谢途径不同于其他蓝藻的常规途径。通过使用一套基因组和建模工具的实验室和现场规模测试相结合，该项目旨在了解微藻的时空动态以及控制微藻属动态和紧急行为的生命规则，从而导致有毒底栖垫。这些结果有望为淡水溪流中底栖有毒垫的生态科学开辟新的机会，并适用于蓝藻华的缓解。该项目将扩大参与范围，促进学生在环境生物学、数据科学、生态工程、化学、数学建模和计算机科学方面的培训，重点是培训来自代表性不足群体的学生。尽管最近的研究发现，有毒和无毒菌株在定植过程中相互协同代谢促进对方，但营养浓度、河床类型和其他环境因素如何在控制微藻定植和毒素产生的生命紧急规则中发挥作用尚不清楚。因此，该项目旨在研究的生命规律是，微藻是如何通过与无毒的对应物和其他共存的底栖垫细菌的相互作用而形成垫和产生毒素的。该项目将研究(1)垫内物种相互作用和生物地球化学条件如何促进微藻在低营养流中的生长和毒素产生；(2)有毒的非异细胞（如微藻）和异细胞蓝藻（能够固定大气氮气的重氮营养菌，如水藻）在缺氮和/或缺磷的流动水中繁殖的分子机制（如基因表达水平）；(3)建立模型，预测河流尺度上有毒微藻的发生和动态，量化蓝藻群落动态和非生物环境条件如何驱动底栖蓝藻和毒素在生长季节的产生。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Rivers and streams make up less than 1 % of the total surface freshwater available on earth, but are of enormous ecological and societal significance. Recently, biofilm forming toxic cyanobacteria, commonly known as benthic harmful cyanobacterial blooms, have become widespread in many rivers and streams. These cyanobacteria produce toxins as secondary metabolites which are harmful to humans and other animals when consumed. Species from the benthic cyanobacterial genus Microcoleus (formerly Phormidium) can form thick mats in flowing freshwaters which produce cyanotoxins in spatial and temporal patterns that are challenging to predict. Microcoleus benthic mats have become widespread and exhibit intriguing emergent behavior. Toxic strains of Microcoleus co-exist with its non-toxic counterparts and other cyanobacteria. Many metabolic pathways of toxic Microcoleus species operate differently from conventional pathways of other cyanobacteria. Through a combination of laboratory and field scale testing using a suite of genomic and modeling tools, this project seeks to understand the spatial and temporal dynamics of Microcoleus and the rule of life controlling the dynamics and emergent behavior of Microcoleus genera leading to toxic benthic mats. The results are expected to open new opportunities in the ecological science of benthic toxic mats in freshwater streams and to be applicable to cyanobacterial bloom mitigation. This project will broaden participation and promote student training in environmental biology, data science, ecological engineering, chemistry, mathematical modeling and computer science with an emphasis on training students from underrepresented groups. Despite recent findings that toxic and non-toxic strains of Microcoleus synergize their metabolic efforts to facilitate each other during colonization, how nutrient concentrations, riverbed type, and other environmental factors play a role in the Emergent Rule of Life governing the colonization and toxin production in Microcoleus are not well understood. Therefore, the rule of life this project aims to investigate is how mat formation and toxin production by Microcoleus emerge from its interactions with its non-toxic counterparts and other coexisting bacteria in the benthic mats. The project will study (1) how within-mat species interactions and biogeochemical conditions facilitate Microcoleus growth and toxin production in low-nutrient streams, (2) the molecular mechanisms (e.g., gene expression level) by which toxic non-heterocytous (e.g., Microcoleus) and heterocytous cyanobacteria (diazotrophs able to fix atmospheric nitrogen gas, e.g., Anabaena) flourish in nitrogen and/or phosphorus deficient flowing waters and, (3) develop models to predict the occurrence and dynamics of toxic Microcoleus at river scales and quantify how cyanobacterial community dynamics and abiotic environmental conditions drive benthic cyanobacteria and toxin production over the growing season.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.