Collaborative Research: Identifying the basis of fitness against protozoan grazing in cyanobacteria: From quantitative genomics to molecular mechanisms

蓝藻是水环境中重要的光合作用微生物，它们在食物链的底部占据着中心位置。此外，某些物种产生毒素，并能够形成有害的藻类水华。由于富营养化和气温上升，预计未来这些水华的发生将会增加。控制蓝藻种群的因素之一是捕食，但人们对蓝藻与捕食者之间相互作用的生化和遗传机制知之甚少。研究人员将识别影响蓝藻对捕食者易感性的基因，以了解捕食机制。这些知识将有助于指导休闲和饮用淡水资源的管理，以及用于生物技术应用的大规模室外蓝藻养殖，因为生物技术应用往往受到捕食者的阻碍。由于有毒藻华具有普遍的公众利益，研究人员将把这一项目的各个方面纳入他们的教学和外展演示文稿中，以使学生和公众参与到科学进程及其对环境问题的应用中。他们还将为未被充分代表的高中生开发一个课程模块，向他们介绍细菌在水环境中的存在、丰富和作用。这个项目涉及蓝藻抵抗原生生物捕食的生理机制。具体地说，该项目的主要目标是识别控制单细胞蓝藻细长聚球藻在变形虫和纤毛虫捕食者选择压力下的适合性的基因和过程。研究人员已经开发了实验室模型系统来研究放牧相互作用，并将使用最先进的随机条形码转座子突变(RB-TnSeq)和组学方法以及遗传、生化和生理方法来研究这些相互作用。他们对阿米巴放牧的初步研究表明，细胞表面的几个成分在提高放牧条件下的适合性方面具有重要意义。研究人员将在这些初步发现的基础上，确定长毛链霉菌O抗原突变体和RB-TnSeq确定的基因突变的其他突变体对阿米巴捕食者的耐牧性机制。他们将进行类似的分析，以确定在游动的纤毛虫食草动物存在的情况下，影响蓝藻适应性的基因和过程。这些比较研究将为蓝藻逃避捕食者的策略提供重要的见解。调查人员还将把这项研究纳入高中生模块，并让本科生、研究生和博士后学者参与研究。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Cyanobacteria are important photosynthetic microorganisms in aquatic environments, where they occupy a central position at the base of the food web. In addition, certain species produce toxins and are capable of forming harmful algal blooms. Occurrences of these blooms are expected to increase in the future due to eutrophication and increasing temperatures. One of the factors controlling cyanobacterial populations is predation, but very little is known about the biochemical and genetic mechanisms governing the interactions between cyanobacteria and their predators. The researchers will identify cyanobacterial genes that affect their susceptibility to predators in order to understand predation mechanisms. This knowledge will be useful in guiding the management of recreational and drinking freshwater resources, and that of large scale outdoor culturing of cyanobacteria for biotechnological applications, which is often hampered by predators. Because toxic algal blooms are of general public interest, the researchers will incorporate aspects of this project into their teaching and outreach presentations to engage students and the public in the process of science and its application to environmental problems. They will also develop a module of classes for underrepresented high school students that will introduce them to the presence, abundance, and role of bacteria in aquatic environments. This project concerns physiological mechanisms underlying the resistance of cyanobacteria to predation by protists. Specifically, the main objective of this project is to identify genes and processes governing the fitness of the unicellular cyanobacterium Synechococcus elongatus under selective pressure by amoebal and ciliate predators. The investigators have developed laboratory model systems to study grazing interactions and will study these interactions with state-of-the-art random barcode transposon mutagenesis (RB-TnSeq) and omics approaches, as well as genetic, biochemical, and physiological methods. Their preliminary work on amoebal grazing has pointed to the importance of several components of the cell surface in increasing fitness under grazing conditions. The investigators will build upon these preliminary findings and identify the mechanism of grazing resistance to amoebal predators in S. elongatus O-antigen mutants and other mutants disrupted in genes identified by RB-TnSeq. They will perform similar analyses to identify genes and processes affecting cyanobacterial fitness in the presence of a swimming ciliate grazer. These comparative studies will provide major insight into cyanobacterial strategies for evasion of predators. The investigators will also incorporate the research into modules for high school students and involve undergraduates, graduates and postdoctoral scholars in the research.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.