Biology subjects

Yancey, C. E.

Publications and source records attributed to Yancey, C. E..

3 recordsLinked to original sources

bioRxiv2022

The Western Lake Erie Culture Collection: A promising resource for evaluating the physiological and genetic diversity of Microcystis and its associated microbiome

Cyanobacteria harmful algal blooms (cyanoHABs) dominated by Microcystis spp. have significant public health and economic implications in freshwater bodies around the world. These blooms are capable of producing a variety of cyanotoxins, including microcystins, that affect fishing and tourism industries, human and environmental health, and access to drinking water. In this study, we isolated and sequenced the genomes of 21 unialgal Microcystis cultures collected from western Lake Erie between 2017-2019. While some cultures isolated in different years have a high degree of genetic similarity (Average Nucleotide Identity >99%), genomic data shows that these cultures also represent much of the breadth of known Microcystis diversity in natural populations. Only 5 isolates contained all the genes required for microcystin synthesis while 2 isolates contained a previously described partial mcy operon. Microcystin production within cultures was also assessed using Enzyme-Linked Immunosorbent Assay (ELISA) and supported genomic results with high concentrations (up to 900 g L-1) in cultures with complete mcy operons and no or low toxin detected otherwise. These xenic cultures also contained a substantial diversity of bacteria associated with Microcystis, which has become increasingly recognized as an essential component of cyanoHAB community dynamics. These results highlight the genomic diversity among Microcystis strains and associated bacteria in Lake Erie, and their potential impacts on bloom development, toxin production, and toxin degradation. This collection significantly increases the availability of environmentally relevant Microcystis strains from temperate North America, which is changing rapidly due to climate change. HighlightsO_LITwenty one xenic Microcystis cultures were isolated from western Lake Erie and capture the diversity of Microcystis strains observed in natural populations as well as their associated bacteria C_LIO_LIMicrocystis strains show variability in core and accessory gene content, and genetically similar strains produce varying concentrations and congeners of microcystins C_LIO_LIThis collection is a valuable resource for studying strain diversity and interactions between Microcystis and associated bacteria C_LIO_LIOur collection increases the availability of environmentally relevant strains from temperate North America, which is historically underrepresented in culture collections. C_LI

microbiology↗

bioRxiv2022

Expression of Microcystis biosynthetic gene clusters in natural populations suggests temporally dynamic synthesis of novel and known secondary metabolites in western Lake Erie

SummaryMicrocystis spp. produces diverse secondary metabolites within freshwater cyanoHABs around the world. In addition to the biosynthetic gene clusters (BGCs) encoding known compounds, Microcystis genomes harbor numerous BGCs of unknown function, indicating its poorly understood chemical repertoire. While recent studies show that Microcystis produces several metabolites in the lab and field, little work has focused on analyzing the abundance and expression of its broader suite of BGCs during cyanoHAB events. Here, we use metagenomic and metatranscriptomic approaches to track the relative abundance of Microcystis BGCs and their transcripts throughout the 2014 western Lake Erie cyanoHAB. Results indicate the presence of several transcriptionally active BGCs that are predicted to synthesize both known and novel secondary metabolites. The abundance and expression of these BGCs shifted throughout the bloom, with transcript abundance levels correlating with temperature, nitrate and phosphorus concentrations, and the abundance of co-occurring predatory and competitive eukaryotic microorganisms, suggesting the importance of both abiotic and biotic controls in regulating expression. This work highlights the need for understanding the chemical ecology and potential risks to human and environmental health posed by secondary metabolites that are produced but unmonitored, as well as the potential discovery of pharmaceutical compounds from cyanoHAB-derived BGCs. Originality-Statement of SignificanceMicrocystis spp. dominate cyanobacterial harmful algal blooms (cyanoHABs) worldwide and pose significant threats to water quality through the production of numerous secondary metabolites, many of which are toxic. While the toxicity and biochemistry of microcystins and several other compounds have been well studied, the broader suite of secondary metabolites produced by Microcystis remains poorly understood, leaving gaps in our understanding of their impacts on ecology, human and ecosystem health, or potential pharmaceutical application. In this study, we use metagenomic and transcriptomic datasets to examine the diversity of genes encoding synthesis of secondary metabolites in natural Microcystis populations and assess their patterns of transcription in the context of biotic and abiotic conditions in western Lake Erie cyanoHABs. Our results reveal the presence of a large diversity of both known gene clusters that encode toxic secondary metabolites as well as novel ones that encode cryptic compounds. This research highlights the need for targeted studies of the secondary metabolite diversity in western Lake Erie, a vital freshwater source to the United States and Canada.

microbiology↗

bioRxiv2022

Transcriptionally active nitrogen fixation and biosynthesis of diverse secondary metabolites by Dolichospermum and Aphanizominom-like Cyanobacteria in western Lake Erie Microcystis blooms

Cyanobacterial harmful algal blooms (cyanoHABs) in the western basin of Lake Erie are dominated by microcystin producing Microcystis spp., but other cyanobacterial taxa that coexist in these communities may play important roles in production of toxins and shaping bloom dynamics and community function. In this study, we used metagenomic and metatranscriptomic data from the 2014 western Lake Erie cyanoHAB to explore the genetic diversity and biosynthetic potential of cyanobacteria belonging to the Anabaena, Dolichospermum, Aphanizomenon (ADA) clade. We reconstructed two near-complete metagenome-assembled genomes from two distinct ADA clade species, each containing biosynthetic gene clusters that encode novel and known secondary metabolites that were transcriptionally active. These taxa also appear to have varying nutrient acquisition strategies, and their ability to fix N may be important for synthesizing N rich metabolites as well as supporting bloom persistence. Although not the dominant organism in this system, these results suggest that ADA may be important community members in western Lake Erie cyanoHABs that have the potential to produce unmonitored toxins. HighlightsO_LIThrough metagenomic approaches, we generated two near-complete metagenome assembled genomes from two distinct species that are dispersed across the ADA clade of cyanobacteria. C_LIO_LIThese ADA cyanobacteria have the potential to produce a variety of known and novel secondary metabolites, and use different nitrogen fixation strategies as observed through differential transcript abundance C_LIO_LIThis works highlights the diversity of cyanobacteria in western Lake Erie blooms despite their continued dominance by Microcystis, and that these less abundant cyanobacteria may produce unmonitored toxins and shape bloom dynamics through N-fixation. C_LI

microbiology↗