title: Molecular and phylogenetic characterization of potentially toxic cyanobacteria in Tunisian freshwaters.
abstract: This study presents a genetic characterization of 27 potentially toxic cyanobacterial strains isolated from seven reservoirs located in the north and centre of Tunisia. These strains belonged mainly to Microcystis aeruginosa, Cylindrospermopsis raciborskii and Planktothrix agardhii species. Their toxicological potential was evaluated by molecular biology tools, which showed that none of the isolated strains carried segments of the gene cluster responsible for the production of cylindrospermopsin and saxitoxin. The majority of Microcystis isolates were able to synthesize microcystin, since they presented the six characteristic segments of the microcystin synthetase mcy cluster (mcyA, -B, -C, -D, -E and -G). This was further confirmed by MALDI-TOF analysis that showed the presence of eight microcystin variants, including microcystin-LR. The taxonomic identification of the strains was assessed based on the variability of the 16S rRNA gene sequences. Furthermore, the 16S-23S rRNA ITS sequences of Microcystis isolates and rpoC1 sequences of Cylindrospermopsis strains were also used in the phylogenetic analysis.
authors.affiliation: Unité de Recherche Ecosystèmes et Ressources Aquatiques, Institut National Agronomique de Tunisie, Tunis Mahrajène, Tunisia.
authors.forename: Afef
authors.initials: A
authors.lastname: Fathalli
authors.forename: Amel Ben Rejeb
authors.initials: AB
authors.lastname: Jenhani
authors.forename: Cristiana
authors.initials: C
authors.lastname: Moreira
authors.forename: Martin
authors.initials: M
authors.lastname: Welker
authors.forename: Mohamed
authors.initials: M
authors.lastname: Romdhane
authors.forename: Agostinho
authors.initials: A
authors.lastname: Antunes
authors.forename: Vitor
authors.initials: V
authors.lastname: Vasconcelos
mesh_terms: D000470:Alkaloids; D001427:Bacterial Toxins; D016000:Cluster Analysis; D000458:Cyanobacteria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D000087522:Cyanobacteria Toxins; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D005618:Fresh Water / Q000382:microbiology*; D052998:Microcystins / Q000096:biosynthesis / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012530:Saxitoxin / Q000235:genetics; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014416:Tunisia; D014498:Uracil / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000470:Alkaloids; D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D052998:Microcystins; D012336:RNA, Ribosomal, 16S; C089595:cylindrospermopsin; D012530:Saxitoxin; D014498:Uracil; C078588:microcystin; D012321:DNA-Directed RNA Polymerases