Comparative study of two isolation methods of Cyanobacteria in Côte d’Ivoire

Cyanobacteria are prokaryotic organisms found in the freshwaters of most countries of the world. Interest in these organisms has increased in recent years because of their ability to produce toxins that are harmful to higher organisms. The objective of this study was to compare two methods of isolation of cyanobacteria in Côte d’Ivoire. Monthly water withdrawals were carried out from June 2016 to March 2018 on the Aghien Lagoon (Côte d'Ivoire) and analyzed using two methods, namely the isolation method on modified BG11 agar and the direct binocular method. A total of 1682 cyanobacteria were isolated, 1593 (94.70%) cyanobacteria were obtained by direct isolation and 89 (5.30%) by seeding isolation. The 1682 cyanobacteria were purified by successive transplanting on the agar BG11 modified, 563 cyanobacteria (33.47%) were obtained. Of this total, 92.36% (n = 520 cyanobacteria) were obtained by the direct method and 7.64% (n = 43 cyanobacteria) by the isolation method on modified BG11 agar. In order to maintain the growth of purified cyanobacteria, the 563 cyanobacteria were transferred to liquid modified BG11 medium. However 38 (6.74%) cyanobacteria had a positive growth on this medium of which 5.76% (n = 30) came from the direct method and 17.02% (n = 8) from the isolation method on modified BG11 agar. This study has shown that the isolation method that has resulted in better yield has been isolation by isolation method on modified BG11 agar.