Molecular Characterization of Potential Microcystin-Producing Cyanobacteria in Lake Ontario Embayments and Nearshore Waters

Abstract

The distribution and genotypic variation of potential microcystin (MC) producers along the southern and eastern shores of Lake Ontario in 2001 and 2003 were examined using a suite of PCR primers. Cyanobacterial, Microcystis sp., and Microcystis-specific toxin primer sets identified shoreline distribution of cyanobacterial DNA (in 97% of the stations) and MC synthetase genes (in 50% of the stations). Sequence analysis of a partial mcyA amplicon targeting Microcystis, Anabaena, and Planktothrix species indicated that the Microcystis sp. genotype was the dominant MC genotype present and revealed a novel Microcystis-like sequence containing a 6-bp insert. Analysis of the same samples with genus-specific mcyE primers confirmed that the Microcystis sp. genotype was the dominant potential MC producer. Genotype compositions within embayments were relatively homogenous compared to those for shoreline and tributary samples. MC concentrations along the shoreline exhibited both temporal and spatial differences as evidenced by the protein phosphatase inhibition assay, at times exceeding the World Health Organization guideline value for drinking water of 1.0 g MC-LR eq liter ؊1 . MC genotypes are widespread along the New York State shoreline of Lake Ontario, appear to originate nearshore, and can be carried through the lake via wind and surface water current patterns.

Spatiotemporal changes in the genetic diversity of a bloom-forming Microcystis aeruginosa (cyanobacteria) population

“…Our findings identified marked spatial variations during the development of the bloom, which was characterized by higher cell abundances in the middle and downstream parts of the reservoir. As in other studies (for example Hotto et al, 2007;Moreno-Ostos et al, 2008), this heterogeneous spatial distribution of Microcystis biomass might have been generated by greater cyanobacterial growth in areas where conditions for growth were better, or by displacement of the population by currents or winds, leading to an accumulation of a high cyanobacterial biomass in some areas. Some findings from the ITS genotyping suggested that both these processes were probably involved in the heterogeneous distribution of Microcystis biomass in the Grangent reservoir.…”

Vertical Heterogeneity of Genotypic Structure and Toxic Potential within Populations of the Harmful Cyanobacterium Microcystis aeruginosa

“…Indeed, at the same time, important differences of biomass can be observed at different sites of a same lake as the result of either different growth rates (because of local variations of resources availability), or current-induced local accumulations [7,25,28]. Such horizontal heterogeneity had already been proven to sometimes result in spatial variations of genotypic structure and toxic potential [25,28]. Our study corroborates this result since both these parameters differed between the different sampling sites we prospected in Grangent reservoir in 2009.…”

“…Understanding the regulation of this temporal genotypic succession is thereafter of major importance. Several putative driving forces have already been proposed: fitness-related selection during the growth period [23,25], contribution from other sites within the ecosystem, through horizontal transport [25,28] or selective interactions with the benthic compartment [14,15,29]. However, such contribution relies on a heterogeneous spatial distribution that is yet to be further characterized within natural populations of M. aeruginosa.…”

“…To date, the spatial heterogeneity within a single population of M. aeruginosa has only been demonstrated in the horizontal dimension, on top of the water column [25,28]. However, because of water column mixing events, of the continuous sedimentation of some colonies of M. aeruginosa throughout the bloom period [29], and of the ability of the colonies to migrate in the water column [30], the colonies of M. aeruginosa are observed throughout the water column.…”

Genetic analysis of the microcystin biosynthesis gene cluster in Microcystis strains from four bodies of eutrophic water in Japan

“…The clarifi cation of mcy genes has enabled the development of molecular methods for the detection and identifi cation of MCYST-producers. MCYST-producers in water samples were detected and quantifi ed by PCR using specifi c primer sets for the mcy genes (Hotto et al, 2007;Rantala et al, 2006;Yoshida et al, 2003). On the other hand, Rantala et al (2004) concluded that the mcy gene was not transferred horizontally between genera based on the phylogenetical relationship between it and housekeeping genes.…”