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Étude des cyanobactéries de la lagune aghien et de leur potentialité à produire des métabolites secondaires

Abstract : The eutrophication of the world's rivers promotes the development of Cyanobacteria. Some species are potentially producing secondary metabolites. However, although some metabolites are toxins that may be dangerous for humans, others may be of interest to biotechnology and the pharmaceutical industry. The objective of this work was to identify Cyanobacteria of the Aghien lagoon and study their potential to produce secondary metabolites Monthly water withdrawals were carried out from June 2016 to March 2018 in the Aghien lagoon near Abidjan in Côte d’Ivoire. Physico-chemical analyzes made it possible to determine the quality of the waters of the lagoon, then microscopic observations and inoculeting on the BG11 medium (solid and liquid) allowed respectively to recognize and isolate the different species of Cyanobacteria contained in these samples. Finally the conventional PCR allowed detecting the genes which code for the synthesis of microcystins, cyanopeptolins, microviridins and aeruginosins. The monitoring of physico-chemical parameters of the Aghien lagoon revealed a relatively important evolution of the conductivity and nutrient salts (phosphorus and phosphate). Chlorophyll (a) contents range from 28.26 μg/L to 95.05 μg/L with maximum values during dry seasons. The genera Microcystis and Chroococcus were the most represented in the collected samples (100%). They are followed by Aphanocapsa (95.45%), Planktothrix (90.90%), Anabeana and Limnotrix (86.36%). The genera Pseudanabaena and Aphanothece were the least highlighted (59.09%). A total of 1682 Cyanobacteria were isolated and purified by successive subcultures on BG11 agar, 563 (33.47%) were obtained. The 563 Cyanobacteria were transferred to liquid modified BG11 medium, 38 (6.74%) Cyanobacteria had positive growth on this medium. The mcyA and mcyD microcystin genes were detected in 93.75% and 62.5% of the samples, respectively. Other secondary metabolites : aeruginosins (aerD), cyanopeptolines (mcnC) and microviridines (mdnB) were obtained in 87.5%, 50% and 18.75% of the samples, respectively. In addition to the microcystin synthesis genes, the Cyanobacteria of the Aghien lagoon have other secondary metabolite genes.
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Djéha Rosine Yao. Étude des cyanobactéries de la lagune aghien et de leur potentialité à produire des métabolites secondaires. Sciences du Vivant [q-bio]. Université Félix Houphouët Boigny (Abidjan, Côte d'Ivoire); Numéro d’ordre 2275 / 2020, 2020. Français. ⟨tel-02883242⟩

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