Isolation of benthic cyanobacteria and screening of bioactivities and natural products from culture collection strains

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Title: Isolation of benthic cyanobacteria and screening of bioactivities and natural products from culture collection strains
Author: Tamrakar, Anisha
Contributor: University of Helsinki, Faculty of Agriculture and Forestry, Department of Food and Environmental Sciences
Publisher: Helsingfors universitet
Date: 2016
Language: eng
Thesis level: master's thesis
Discipline: Mikrobiologi
Abstract: Cyanobacteria are well known for their ability to produce wide variety of natural products, many of which exhibit antimicrobial, antifungal, antiviral or anticancer properties. These products include peptides, polyketides, alkaloid and polysaccharides. Cyanobacteria are also infamous for its toxic blooms, which are health hazardous to human, as well as animals. In this study, new benthic cyanobacterial strains were isolated from the Varlaxudden Seashore, Porvoo, Finland. The strains were purified and identified using microscopy. In addition, Finnish cyanobacterial strains (UHCC) and Brazilian strains (CENA) were screened for bioactive compounds. The 16S rRNA gene from UHCC and CENA strains were sequenced and used for the strain identification as well as to determine phylogenetic relationships. Bioactivities of strains were tested by disk diffusion assay followed by LC-MS and HPLC analysis to detect bioactivity as well as the bioactive compounds. The isolation of strains from 48 samples resulted in 48 morphologically identified cyanobacterial strains; 36 of them were Calothrix, 5 Anabaena, 4 Nostoc and one each of Tolypothrix, Scytonema and Cyanotheca genera. Four of the Calothrix strains (VAR 5/1, VAR 20/2, VAR 30/2 and VAR 43) were successfully made axenic. The UHCC and CENA strains included in this study belonged to two different habitats and regions (temperate and tropical) and a huge diversity between the strains were observed in the phylogenetic tree. A total of 12 of the studied cyanobacterial strains exhibited antifungal and antibacterial activities. A new peptide was observed from Nostoc sp. Brazil Punan but isolation was not successful. Three Nostoc strains produced hassallidins. Nostoc sp. SMIX 1 produced an antifungal compound, puwainaphycins which included two old and four new variants. The study also revealed cyanobacterial strains showing bioactivities but the bioactive compounds remained unidentified. So, further analyses are still needed for isolation and characterization of the unidentified compounds. Therefore, this study shows that cyanobacteria are prolific source of bioactive compounds and also potential leads for drug discovery.
Subject: cyanobacteria
bioactive compounds

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