Highly Toxic Microcystis aeruginosa Strain, Isolated from São Paulo—Brazil, Produce Hepatotoxins and Paralytic Shellfish Poison Neurotoxins

Abstract

While evaluating several laboratory-cultured cyanobacteria strains for the presence of paralytic shellfish poison neurotoxins, the hydrophilic extract of Microcystis aeruginosa strain SPC777--isolated from Billings's reservoir, São Paulo, Brazil--was found to exhibit lethal neurotoxic effect in mouse bioassay. The in vivo test showed symptoms that unambiguously were those produced by PSP. In order to identify the presence of neurotoxins, cells were lyophilized, and the extracts were analyzed by HPLC-FLD and HPLC-MS. HPLC-FLD analysis revealed four main Gonyautoxins: GTX4(47.6%), GTX2(29.5%), GTX1(21.9%), and GTX3(1.0%). HPLC-MS analysis, on other hand, confirmed both epimers, with positive Zwitterions M(+) 395.9 m/z for GTX3/GTX2 and M(+) 411 m/z for GTX4/GTX1 epimers.The hepatotoxins (Microcystins) were also evaluated by ELISA and HPLC-MS analyses. Positive immunoreaction was observed by ELISA assay. Alongside, the HPLC-MS analyses revealed the presence of [L: -ser(7)] MCYST-RR. The N-methyltransferase (NMT) domain of the microcystin synthetase gene mcyA was chosen as the target sequence to detect the presence of the mcy gene cluster. PCR amplification of the NMT domain, using the genomic DNA of the SPC777 strain and the MSF/MSR primer set, resulted in the expected 1,369 bp product. The phylogenetic analyses grouped the NMT sequence with the NMT sequences of other known Microcystis with high bootstrap support. The taxonomical position of M. aeruginosa SPC777 was confirmed by a detailed morphological description and a phylogenetic analysis of 16S rRNA gene sequence. Therefore, co-production of PSP neurotoxins and microcystins by an isolated M. aeruginosa strain is hereby reported for the first time.

A review of the global ecology, genomics, and biogeography of the toxic cyanobacterium, Microcystis spp.

“…Since this finding has not been replicated in the past two decades of intensive cyanobacterial research, it remains possible that the anatoxin-a measured in these cultures was derived from a co-cultured microbe. Similarly, an isolate of Microcystis from a lagoon in São Paulo (Brazil; SPC 777) was reported to produce a range of paralytic shellfish poison (PSP) neurotoxins (Sant'Anna et al, 2011). Upon sequencing the genome of the isolate however, no saxitoxin biosynthesis genes were identified casting significant doubt that Microcystis was truly the causative agent.…”

Tropical cyanobacterial blooms: a review of prevalence, problem taxa, toxins and influencing environmental factors

“…This toxin was produced by blooms of Cylindrospermopsis and Lyngbya in Brazil, Mexico, Guatemala and Nigeria (Lagos et al, 1999;Bouvy et al, 1999;Molica et al, 2005;dos Anjos et al, 2006;Berry and Lind, 2010;Rejmánková et al, 2011;Sant'Anna et al, 2011). Comparisons of the neurotoxic Cylindrospermopsis strains from Brazil and Mexico revealed the Brazilian strain to have acute neurotoxicity from the presence of saxitoxin, neosaxitoxin and decarbamoylsaxitoxin and the Mexican strains isolated were found to be non-toxic .…”

Accelerated eutrophication and toxicity in tropical reservoir water and sediments: an ecotoxicological approach

“…Many studies have evidenced the occurrence of cyanobacteria toxic strains in tropical and subtropical reservoirs, as well as in freshwater and saline lakes at different regions of Brazil (Sant'anna et al 2008;Di Bernardo et al 2010;Soares et al 2013) as more and more water bodies become eutrophicated. Although Microcystis aeruginosa was widely the most representative among the toxic species (Azevedo et al 1994;Matthiensen et al 1999;Sant'anna et al 2011;Bortoli et al 2014), in the last decade, C. raciborskii is becoming frequent in many regions of the country, including the southeast region (Barbosa et al 1999;Dellamano-Oliveira et al 2008;Gomes et al 2013).…”