Spatiotemporal changes in the genetic diversity in French bloom‐forming populations of the toxic cyanobacterium, Microcystis aeruginosa

Abstract

Microcystis aeruginosa is a toxic cyanobacterium, which is able to bloom in a wide range of freshwater ecosystems. By sequencing the Internal Transcribed Spacer (ITS) of the ribosomal operon, we compared the genetic composition of several French bloom-forming M. aeruginosa populations from two reservoirs located on the Loire River, at two sampling points located between these reservoirs, and finally in two ponds closely linked to this river. No significant difference was found in the genetic diversity of the six Microcystis populations but we evidenced a strong genetic differentiation between most of these populations. Indeed, the Microcystis population in the Grangent reservoir was genetically differentiated from the other three populations sampled further downstream, implying that no massive transfer of population occurs from this reservoir to downstream segments. We also found genetic differentiation between the populations from the two ponds, and between these populations and those from the Loire River. On the other hand, the same dominant genotype was found in the populations sampled both in the river and in the Villerest reservoir, suggesting the selection of a distinct genotype adapted to river conditions and also an accumulation of this genotype in the downstream reservoir. Finally, by comparing our ITS sequences with those available in the GenBank, no biogeographical differentiation could be detected at a global scale, suggesting that most of the Microcystis genotypes seem to be ubiquitous.

Genetic Diversity of Bloom-Forming Microcystis (Cyanobacteria) Populations in a Hyper-Eutrophic Pond in Central China

“…Considerable studies have been performed on the genotypic composition of Microcystis blooms. Recent developments in elucidating the genetic diversity of Microcystis blooms by sequencing the environmental rRNA genes, such as internal transcribed spacer (ITS), have provided new insight into the genetic diversity of Microcystis populations in freshwaters [1,2,15]. Briand et al [2] obtained 306 different genotypes from 784 ITS sequences in a France reservoir.…”

“…They also found that marked changes occurred in the ITS genotype composition of M. aeruginosa populations during the development of the bloom. Sabart et al [15] compared the genetic composition of several French bloom-forming Microcystis populations from different water systems along the Loire river. They obtained a total of 379 ITS genotypes among 950 ITS sequences.…”

Genetic analysis on Dolichospermum (Cyanobacteria; sensu Anabaena) populations based on the culture-independent clone libraries revealed the dominant genotypes existing in Lake Taihu, China

“…This finding added a better understanding the spatiotemporal dynamics of cyanobacterial blooms dominated by filamentous cyanobacteria in freshwater ecosystems. Comparative results from ITS sequences between Microcystis and Dolichospermum blooms in Lake Taihu, demonstrated that genetic diversity (represented as values of genotype number/ITS sequence number) from Microcystis blooms was higher than that from Dolichospermum blooms (Bozarth et al, 2010;Sabart et al, 2009). These studies on genotypes of Microcystis dominated blooms, from river-based reservoirs with large surface areas and certain degrees of water flow and pond systems, indicated that strong hydrodynamics influence may trigger the selection of the main genotypes.…”

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

“…Our study corroborates this result since both these parameters differed between the different sampling sites we prospected in Grangent reservoir in 2009. Associated to the dynamics resulting from growth and decay, horizontal heterogeneity was hence supposed to be one of the main drivers of the high temporal variability of toxic potential and genotypic structure that were frequently reported in blooms of M. aeruginosa [4,8,22,23,25,26,38,39]. Now, the vertical heterogeneity we observed through this study represents a third part to consider in order to fully understanding the temporal dynamics of genetic diversity and toxin production in M. aeruginosa's blooms.…”

“…Many comprehensive studies have therefore been realized in order to explain the ecological success of this cyanobacterium and to unravel the complex set of factors driving both its dynamics and its toxicity. Such previous studies mainly dealt with the genetic diversity of M. aeruginosa's populations [4][5][6][7], the toxic potential of M. aeruginosa [8][9][10][11][12], and the determinism of the different steps of M. aeruginosa's life cycle [13][14][15][16].…”