Project description:Harmful algal blooms present severe environmental threats, impacting water quality, aquatic ecosystems, and human health. The frequency and intensity of these blooms are rising, largely driven by global warming and changing climatic conditions. There is an urgent need for innovative methods to monitor blue-green algae, also known as cyanobacteria, to enable the implementation of preventative measures. Here, we show that native mass spectrometry is an effective tool for detecting cyanobacteria directly from lake samples, both prior and during bloom formation. Our approach allows for the rapid characterization of cyanobacterial populations within lakes, offering valuable insights into the dynamics of cyanobacterial species associated with harmful algae blooms. Overall, we highlight the exceptional capability of native mass spectrometry in directly detecting and monitoring cyanobacterial blooms, which will support the development of more effective strategies to mitigate this growing environmental challenge.
Project description:Rapid assessment of phytoplankton assemblages using Next Generation Sequencing – Barcode of Life database: a widely applicable toolkit to monitor biodiversity and harmful algal blooms (HABs)
Project description:Cyanobacteria are photosynthetic prokaryotes vital to global biogeochemical cycles. However, some form harmful algal blooms (cyanoHABs) that disrupt ecosystems and produce toxins. The mechanisms by which these blooms form have yet to be fully understood, particularly the role of extracellular components. Here, we present a 2.4 Å cryo-EM structure of a pilus, termed the cyanobacterial tubular (CT) pilus, found in the cyanoHAB-forming species Microcystis aeruginosa. The pilin exhibits a novel protein fold, forming a tubular pilus structure with tight, double-layer anti-parallel β-sheet interactions. We show that CT pili are essential for buoyancy by facilitating the formation of micro-colonies, which increases drag force and prevents sinking. Furthermore, the CT pilus surface is heavily glycosylated with ten monosaccharide modifications per pilin. We also found that CT pili can enrich microcystin, potentially enhancing cellular resilience, and co-localize with iron-enriched extracellular matrix components. Thus, we propose that this pilus plays an important role in the proliferation of cyanoHABs. This newly discovered pilus family appears to be widely distributed across several cyanobacterial orders, including Chroococcales, Nostocales, and Synechococcales. Our structural and functional characterization of CT pili provide insights into cyanobacterial cell morphology, physiology, and toxin interactions, and identify potential targets for disrupting bloom formation.
Project description:Harmful algal blooms (HABs) arise from the rapid growth of algae in both marine and freshwater ecosystems due to the continuous global temperature rise and anthropogenic eutrophication. Humans are at a great risk of exposure to toxins released from HABs through drinking water, food, and recreational activities, making HAB toxins contaminants of emerging concern (CECs). The impact of HAB toxins on women’s reproductive health, however, remains poorly understood. Here, we investigated the effects of microcystin-LR (MC-LR), the most common HAB toxin, on the ovary, the female gonad, and associated ovarian functions. The results of a chronic daily oral mouse exposure model and an acute exposure using the mouse superovulation model revealed that MC-LR accumulated in the ovary and environmentally-relevant exposure to MC-LR perturbed follicle-stimulating hormone (FSH)-dependent follicle maturation to disrupt ovulation and luteinization. Using an ex vivo mouse follicle maturation and ovulation assay and in vitro culture of human primary granulosa cells, mechanistic studies such as the single-follicle RNA sequencing analysis and others elucidated that MC-LR inhibited protein phosphatase 1 (PP1) and interfered with PP1-mediated PI3K/AKT/FOXO1 signaling in granulosa cells, which suppressed follicle maturation, ovulation, luteinization, and progesterone secretion. Together, our study demonstrates that environmentally-relevant exposure to MC-LR acts a PP1 inhibitor to interfere with the PI3K/AKT/FOXO1 signaling in granulosa cells, which disrupts follicle maturation and results in adverse female reproductive outcomes. As a newly identified ovarian endocrine disrupting chemical (EDC), exposure to MC-LR poses a serious threat to women’s reproductive health and fertility.
Project description:In environmental ecosystems, vitamin concentrations are often exceedingly low and auxotrophy, or reliance on exogenous vitamin or vitamin precursors, is widespread. We show here that the widespread harmful algal bloom (HAB) species Microcystis aeruginosa, threatening freshwater aquatic ecosystems globally, releases a complex mixture of thiamin antivitamins, including bacimethrin and methoxythiamin, which induce thiamin deficiency in the model green alga Chlamydomonas reinhardtii. Putative biosynthetic genes for bacimethrin were upregulated in M. aeruginosa when grown in co-culture resulting in greater production of bacimethrin. Bacimethrin, methoxythiamin, oxidized forms of thiamin and methoxythiamin, and a novel structural homolog of bacimethrin were all found at elevated levels in the co-culture exometabolome extracts and were all inhibitory to the growth of C. reinhardtii individually at very low concentrations and as a mixture in culture medium extracts. The thiamin-requiring mutant C. reinhardtii, CC-25, was much more sensitive to bacimethrin and methoxythiamin than the wildtype. Thiamin addition largely rescued the inhibitory effects of exposure to antivitamins in both the wildtype and mutant strain. Finally, we determined that bacimethrin is present in aquatic environments and is elevated during Microcystis blooms. Thus, allelopathic suppression of competitors, particularly those that are auxotrophic for thiamin, by M. aeruginosa via the production of antivitamins in environments where thiamin availability is low, could help this species to become dominant and form blooms