Microcystis aeruginosa

Cyanobacteria are ancient prokaryotes that use photosynthesis and an accumulation of other adaptations to dominate aquatic ecosystems around the world. They are thus major contributors to biogeochemical cycling, a threat to human and environmental health, and an intriguing source for novel chemistry. We begin by providing an overview of bloom-forming cyanobacteria and their many toxic metabolites. We then discuss the characterization of some abundant extracellular pili of Microcystis aeruginosa, reporting a 2.4 Å cryoelectron microscopy pilus structure, revealing a novel class of pili that we have termed cyanobacterial tubular (CT) pili. The CT pili in M. aeruginosa were determined to be multi-functional, with a primary role in networking cells and enhancing colony formation, but also in controlling colony buoyancy, enriching iron, and accumulating toxins in the extracellular mucilage. Lastly, we explore the potential of heavy-labeling cyanobacterial cultures for the sake of isolating natural products that can be studied by vibrational spectroscopic imaging. The vibrational spectra of three classes of cyanopeptides along with their heavy-labeled counterparts are reported, and Density Functional Theory calculations are used to describe mode character, clarifying some unexpected changes in vibrational spectra upon heavy-labeling. As a whole, this work offers new insight into cyanobacterial physiology as well as a means to study cyanopeptides with imaging techniques and stable-isotope labeling.

Freshwater harmful algal blooms (HABs) are increasing in severity and frequency. These blooms are devastating to the communities surrounding these bodies of water due to their numerous health, economic, and environmental impacts (Hallegraeff et al. 1995; Smith 2003; O’Neil et al. 2012; Bláha et al. 2009; V. H. Smith et al. 1999). In Florida, runoff containing fertilizers, human wastes, or industrial wastes contribute to the eutrophication in these lakes and contribute to these freshwater blooms (Val H. Smith 2003; Heisler et al. 2008; O’Neil et al. 2012). M. aeruginosa, a toxic cyanobacterium, often devastates Lake Okeechobee. M. aeruginosa die off creates anoxic conditions and produces a toxin that causes major environmental loss. This project is aimed to increase knowledge on how organic phosphorus compounds affect the growth of the axenic M. aeruginosa and investigate the postulated interactome (Cook et al. 2020). Through these experiments, it was shown that axenic M. aeruginosa cannot utilize organic phosphorus compounds and therefore shows no growth when grown in this media. This research is critical to furthering our understanding of the mechanisms behind these blooms and to mitigating them.