Diversity of microcystin-producing genotypes in Brazilian strains of Microcystis (Cyanobacteria)

Abstract

Microcystis Kützing ex Lemmermann is among the genera of cyanobacteria often associated to toxic blooms with the release of microcystins. A gene cluster codes for microcystin synthetases, which are involved in the biosynthesis of this toxin. The aim of the present study was to investigate the genetic diversity of the mcyB gene, specifically the B1 module, in Brazilian strains of Microcystis spp. and its microcystin variants. Broad genetic diversity was revealed in this region. From the phylogenetic analysis, three clusters were obtained that were not related to the geographic origin or morphospecies of the strains, nor with the variant of the microcystin produced. A group of strains that did not produce microcystins was found, despite the presence of the mcyB1 fragment. Eight microcystin isoforms were detected: MC-LR, [D-Asp³]-MC-LR, [Asp³]-MC-LR, MC-RR, [Dha7]-MC-LR, MC-LF, MC-LW and [D-Asp³, EtAdda5]-MC-LH, the latter of which is described for the first time in Brazil. Moreover, five other variants were not identified and indicate being new.

Sensitivity of salad greens (Lactuca sativa L. and Eruca sativa Mill.) exposed to crude extracts of toxic and non-toxic cyanobacteria

“…Its biosynthesis depends among others, on an enzymatic complex encoded by a gene cluster of microcystin synthetase (mcy) (Tillett et al, 2000). Strains of M. aeruginosa containing these genes are potential producers of the toxin, and those that do not have the genes are incapable of producing MCs (Bittencourt-Oliveira et al, 2011).…”

Microcystins production and antibacterial activity of cyanobacterial strains of Synechocystis, Synechococcus and Romeria isolated from water and coral reef organisms of Brazilian coast

“…The toxic strains can be identified by the presence of mcy gene encoding the polyketide synthases and peptide synthetases involved in the biosynthesis of microcystins (Ross, Santiago-Vázquez, & Paul, 2006; Dyble, Fahnenstiel, Litaker, Millie, & Tester, 2008). Among the mcy genes, a region of the mcyB, has been often used as a molecular marker for the detection of microcystin producers (Bittencourt-Oliveira, 2003; Dyble et al, 2008;Bittencourt-Oliveira, Oliveira, & Pinto, 2011).The importance of secondary metabolites of cyanobacteria and unicellular algae with antimicrobial properties has been extensively revised by Senhorinho, Ross and Scott (2015). Additionally, the antibacterial and antifungal activity of cyanobacteria exometabolites has been previouly reported by Volk and Furkert (2006) and Ramos et al (2015).…”

“…The toxic strains can be identified by the presence of mcy gene encoding the polyketide synthases and peptide synthetases involved in the biosynthesis of microcystins (Ross, Santiago-Vázquez, & Paul, 2006;Dyble, Fahnenstiel, Litaker, Millie, & Tester, 2008). Among the mcy genes, a region of the mcyB, has been often used as a molecular marker for the detection of microcystin producers (Bittencourt-Oliveira, 2003;Dyble et al, 2008;Bittencourt-Oliveira, Oliveira, & Pinto, 2011).…”

Interactions of Toxic Metals with Algal Toxins Derived from Harmful Algal Blooms

“…Commonly, X is Leucine, arginine or tyrosine while Y is alanine, arginine or tyrosine (Luukkainen et al 1993;Gehringer et al 2005;Bittencourt-Oliveira et al 2011). Currently there are over 80 variants of microcystins that have been reported (Xiao et al 2010).…”

“…The most famous intoxication occurred in 1996, when an acute poisoning caused 50 people to die in Brazil by the unusual exposure of microcystins through hemodialysis at a dialysis center as the result of usage of microcystins contaminated water from a nearby water reservoir without treatment (Pouria et al 1998;Yuan et al 2006;Bittencourt-Oliveira et al 2011). Furthermore, increasing evidence points toward the observation that low-level but long-term exposure to microcystins may cause primary liver cancer (Nishiwakimatsushima et al 1992;Zhou et al 2002;Gan et al 2010;Fujiki and Suganuma 2011).…”