|267-3||Consequences of intraspecific diversity in worldwide dispersal and success of harmful cyanobacteria|
|Autores:||Claudia Piccini (IIBCE - Instituto de Investigaciones Biológicas Clemente Estable) ; Luis Aubriot (FCIENCIAS. UDELAR - Facultad de Ciencias, Universidad de la República) ; Sylvia Bonilla (FCIENCIAS. UDELAR - Facultad de Ciencias, Universidad de la República) |
Cyanobacteria are highly successful in modern aquatic systems worldwide. These organisms reach high abundances and form toxic blooms from the tropics to the high latitudes, affecting severely diverse ecosystems. Proliferation of bloom-forming species of cyanobacteria is promoted by eutrophication and high temperature. It is possible to identify differences in their functional traits and environmental preferences linked to intraspecific diversity (ecotypes) and phylogeny. Although information regarding cyanobacterial diversity and toxicity is abundant, little is known about how intraspecific diversity may explain the success of bloom-forming populations through their different ecological preferences and toxic capabilities. Using isolates of Cylindrospermopsis raciborskii, a toxic invasive species as a model, we analyzed if ecological preferences (measured as growth behavior under different environmental conditions, tolerance to temperature and phenotypic changes) are linked to intraspecific diversity, toxin production and molecular phylogeny. Phylogenetic analysis using ITS, nifH gene and rep-PCR showed that the Uruguayan strains clustered together to other C. raciborskii isolated from the Americas, especially to those from Brazil. In addition, nifH-based phylogeny allowed detecting subclusters inside American populations, suggesting an early spread of the species within the continent. Integrating phenotypic and genotypic information from the isolates, we suggested that they could be identified as different ecotypes whose success is subject to local environmental conditions. In addition, current hypothesis support that the ability of C. raciborskii to produce the toxin cylindrospermopsin (CYN) originates in Australian strains and subsequently radiated to Europe and Asia but not to the Americas. When toxin production was addressed in our strains by different analytical techniques, we found that the studied ecotypes are saxitoxin-producers but not able to produce cylindrospermopsin (CYN). Interestingly, these non-CYN producing ecotypes isolated from South America harbor the gene cluster involved in the synthesis of this toxin, questioning the current hypothesis and setting the widespread question about how intraspecific diversity (phenotypic, genotypic and toxin production) is related to proliferation and success of this cyanobacteria in the world.
Palavras-chave: cyanobacteria, Cylindrospermopsis, intraspecific diversity