Preliminary evidence on the presence of cyanobacteria and cyanotoxins from culture enrichments followed by PCR analysis: new perspectives from Africa (Mali) and South Pacific (Fiji) countries.

Cyanobacteria are a group of microorganisms that can be found in a diverse range of biogeographical areas and produce potent and damaging cyanotoxins, which reveal importance for continuous studies and surveillance efforts. In this study, we analyzed worldwide two-month culture-enriched water samples collected from 12 distinct countries (Costa Rica, Cuba, Fiji, France, Indonesia, Mali, Portugal, South Africa, Spain, Thailand, USA, Vietnam) including two undisclosed areas (Fiji and Mali). We performed a PCR-based molecular multi-step scheme that consisted in the detection of the main cyanobacterial species, genera, and cyanotoxins biosynthesis genes. Results from this study indicate that Microcystis aeruginosa followed by Planktothrix agardhii were the most prevalent species of all the 12 countries analyzed. Cylindrospermospis raciborskii was detected in Costa Rica, while P. agardhii was detected in Fiji and South Africa. M. aeruginosa was detected in Fiji and Mali. Regarding the main cyanotoxins biosynthesis genes, a cyrC gene fragment (cylindrospermopsins) was amplified in the African continent (South Africa), while anaC (anatoxin-a) was detected in two distinct locations, Mali and Vietnam. Saxitoxins biosynthesis gene was also detected in Fiji and Vietnam. Microcystins biosynthesis gene (mcyA) was co-detected with anatoxin-a biosynthesis gene in Mali and with saxitoxins biosynthesis gene (sxtI) in Portugal. This study therefore constitutes a major contribution to the global biogeography of cyanobacteria and its cyanotoxins and recommends continuous vigilance of toxic cyanobacteria particularly in the more undisclosed areas of the world. The PCR analysis data obtained in our 2-month culture-enriched water samples supports molecular methods as a preliminary tool in the environmental surveillance of cyanobacteria and cyanotoxins in undisclosed locations, particularly since the several positive amplifications detected may indicate that though samples were collected under non-bloom conditions, if environmental conditions change in the ecosystem, there is a risk that bloom-forming species may arose along with their detected cyanotoxicity.