GENETIC VARIABILITY OF BRAZILIAN STRAINS OF THE MICROCYSTIS AERUGINOSA COMPLEX (CYANOBACTERIA/CYANOPHYCEAE) USING THE PHYCOCYANIN INTERGENIC SPACER AND FLANKING REGIONS (cpcBA)

Abstract

The genetic and morphological variability among 15 Brazilian strains of Microcystis aeruginosa (Kütz.) Kütz. collected from four locations was examined and compared with several reference strains of M. aeruginosa, M. viridis (A. Br.) Lemm. and M. wesenbergii (Kom.) Kom. in Kondr. Brazilian strains were classified by morphological features and by comparison of the nucleotide sequences of the cpcBA intergenic spacer and flanking regions. Our results indicate that Brazilian strains classified as M. aeruginosa are phylogenetically diverse compared with reference strains of M. aeruginosa and that the current taxonomy underestimates genetic diversity within M. aeruginosa. The data also demonstrate that morphological criteria alone are inadequate to characterize Microcystis species. Although colonial characters were shown to vary considerably in culture, some genetic lineages demonstrated consistent cellular diameter ranges, indicating that cell size has value as a taxonomic character. The detection of six M. aeruginosa genotypes in a single water body indicates that morphological approaches can also seriously underestimate the diversity of Microcystis bloom populations.

Genetic Variation of the Bloom-Forming CyanobacteriumMicrocystis aeruginosawithin and among Lakes: Implications for Harmful Algal Blooms

“…Although past studies describing genetic variation of phytoplankton have shown both little variability (i.e., 0 to 10% [1,5,29]) and much variability (i.e., 50 to 100% [2,19,33]), recent studies of cyanobacteria suggest considerable genetic diversity both among sites (3,4,22,25,27,37) and within lakes (2,25,29,46,62). In contrast, three recent studies suggest low genetic diversity for certain cyanobacteria (1,21,24).…”

“…In that study, nine distinct genotypes were collected from four sites, with (at most) six genotypes collected from one site and one specific genotype collected from two sites. Additionally, one unique genotype of M. aeruginosa was collected from the same site over time and along a depth gradient at the same sampling time (2). Most recently, Janse et al (25) surveyed the genetic diversity of 107 Microcystis colonies (seven morphospecies) from 15 European lakes and characterized 59 distinct genetic classes, demonstrating significant genetic variation within and across habitats.…”

“…We found only one instance of the same genotype being present in two separate lakes (ClarkB02/PineCD02/PineCF02/ PineCG02). Although genetic variability of cyanobacteria (13,37), including M. aeruginosa (2,25,62), has been documented previously, this data set represents the most comprehensive genetic analysis of M. aeruginosa strains collected from within and among lakes in North America (see reference 25 for a survey of Microcystis morphotypes throughout Europe). Furthermore, we note that if different colony morphologies (e.g., M. botrys, M. flos-aquae, M. ichthyoblabe, M. viridis, and M. wesenbergii) represent different strains within M. aeruginosa, then we may have underestimated the genetic diversity of this bloom-forming phytoplankter, because we limited our collections to only those morphologies that are typical of M. aeruginosa (i.e., our conclusion of "high" diversity is therefore conservative).…”

“…For example, toxic and nontoxic genotypes within a HAB species might dominate in different habitats and at different times, which could lead to variation in, for example, the ability of consumers to control HABs. However, few studies have measured the genetic composition of HAB populations across time (28,29) or space (2,25), limiting our ability to assess the degree to which environmental variation may select for genotypes with different ecological traits.…”

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

“…In attempts to find out what governs cyanobacterial proliferations, over the past 10 years an increasing number of papers have dealt with the relative importance of biological, physicochemical and weather (for example Wiedner et al, 2002;Jacquet et al, 2005;Catherine et al, 2008). Furthermore, several publications have recently investigated the genetic diversity of some bloom-forming cyanobacterial populations, to assess their population structure (for example Barker et al, 2000;Wilson et al, 2005;Tanabe et al, 2007) or to find out whether biogeographic differentiation occurs between these populations at different spatial scales (for example Bittencourt-Oliveira et al, 2001;Hayes et al, 2002;Laamanen et al, 2002;Gugger et al, 2005).…”