Identifying the source of unknown microcystin genes and predicting microcystin variants by comparing genes within uncultured cyanobacterial cells

While multiple phylogenetic markers have been used in the culture independent study of microcystin producing cyanobacteria, in only a few instances have multiple markers been studied within individual cells, and in all cases these studies have been conducted with cultured isolates. Here, we isolate and evaluate large DNA fragments (\u3e 6 kb) encompassing two genes involved in microcystin biosynthesis (mcyA2 and mcyB1) and use them to identify the source of gene fragments found in water samples. Further investigation of these gene loci from individual cyanobacterial cells allowed for improved analysis of the genetic diversity within microcystin producers as well as a method to predict microcystin variants for individuals. These efforts have also identified the source of the novel mcyA genotype previously termed Microcystis-like that is pervasive in the Laurentian Great Lakes and predict the microcystin variant(s) that it produces

Lake Erie \u3cem\u3eMicrocystis\u3c/em\u3e: relationship between microcystin production, dynamics of genotypes and environmental parameters in a large lake

Cyanobacteria of genus Microcystis sp. have been commonly found in Lake Erie waters during recent summer seasons. In an effort to elucidate relationships between microcystin production, genotypic composition of Microcystis community and environmental parameters in a large lake ecosystem, we collected DNA samples and environmental data during a three-year (2003–2005) survey within Lake Erie and used the data to perform a series of correlation analyses. Cyanobacteria and Microcystis genotypes were quantified using quantitative real-time PCR (qPCR). Our data show that Microcystis in Lake Erie forms up to 42% of all cyanobacteria, and that Microcystis exists as a mixed population of potentially toxic and (primarily) non-toxic genotypes. In the entire lake, the total abundance of Microcystis as well as the abundance of microcystin-producing Microcystis is strongly correlated with the abundance of cyanobacteria suggesting that Microcystis is a significant component of the cyanobacterial community in Lake Erie during summer seasons. The proportion of total Microcystis of all cyanobacteria was strongly linked to the microcystin concentrations, while the percentage of microcystin-producing genotypes within Microcystis population showed no correlation with microcystin concentrations. Correlation analysis indicated that increasing total phosphorus concentrations correlate strongly with increasing microcystin concentrations as well as with the total abundance of Microcystis and microcystin-producing Microcystis

The diversity and distribution of toxigenic \u3cem\u3eMicrocystis\u3c/em\u3e spp. In present day and archived pelagis and sediment samples from Lake Erie

The reoccurrence of significant cyanobacterial blooms in Lake Erie during the last 13 years has raised questions concerning the long-term persistence of microcystin-producing cyanobacteria and the presence of natural sediment reservoirs for potentially toxic cyanobacteria in this large lake system. To address these questions, we analyzed phytoplankton and sediment samples which were collected and preserved in the 1970s as well as samples collected in 2004 from locations within Lake Erie. The identification of microcystin-producing cyanobacteria in Lake Erie was examined via PCR amplification of the mcyA gene fragment. Based on the high % sequence similarity, the mcyA sequences from all 1970s phytoplankton and sediment samples were determined to belong to Microcystis spp., in spite of reports suggesting that Lake Erie was dominated by filamentous cyanobacteria in the 1970s. In sediment samples from 2004, signature genes for Microcystis were distributed and preserved not only in the surface sediments but also up to 10–12 cm in depth. Based on cell quantities determined by a quantitative polymerase chain reaction (qPCR) method, 0.18% of eubacteria in the sediments were Microcystis cells, of which 4.8% were potential microcystin producers. In combination with experiments showing that Microcystis cells can be cultured from Lake Erie surface sediments, this paper demonstrates the potential for these sediments to act as a reservoir for pelagic Microcystis populations and that the composition of the population of microcystin-producing cyanobacteria in Lake Erie has not changed remarkably since the 1970s

The genetic and ecophysiological diversity of Microcystis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/171576/1/emi15615.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/171576/2/emi15615-sup-0002-FigureS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/171576/3/emi15615_am.pd