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

University Of California-San Diego, La Jolla CA

Investigators

Abstract

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.