Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Bioprospecting of cyanobacteria thriving in semi arid regions of Rajasthan

Auteur : Tomer, Anuj Kumar

Université de soutenance : Central University of Rajasthan

Grade : Doctor of Philosophy (PhD) in Microbiology 2021

Résumé partiel
Cyanobacteria are ancient photoautotrophic microorganisms that have been found in almost all ecosystems of Earth including semi-arid environments. Nowadays, extreme environments have attracted the researchers worldwide for the characterization of cyanobacteria and evaluate their biotechnological significances. Semi-arid regions including hypersaline alkaline lake (Sambhar Lake) of Rajasthan are less explored for the characterization of cyanobacteria by employing both conventional as well as molecular approaches. These regions may possess novel cyanobacteria in terms of taxonomy. Cyanobacterial taxa thriving in the diverse habitats of semi-arid regions may be good source of natural compounds. Therefore, aim of the present study was to isolate and characterize cyanobacterial taxa inhabiting different habitats such as aquatic, terrestrial and hypersaline-alkaline lake of semi arid regions of Rajasthan and also to evaluate their biotechnological potentials in terms of pigments, antioxidants properties and UV protecting compounds. A total of thirty-five cyanobacteria was isolated that belonged to five orders such as Chroococcales, Synechococcales, Spirulinales, Oscillatoriales and Nostocales. Among these orders, the genera such as Cyanobacterium, Synechocystis, Euhalothece, Leptolengybya, Haloleptolyngbya, Psedanabaena, Spirulina, Laspinema, Desertifilum, Chlorogloeopsis, Nostoc, Alinostoc, Cyanospira and Scytonema were documented. Based on the 16S rRNA gene sequence analysis, fifteen cyanobacterial isolates showed less than 98 % 16S rRNA gene sequence similarity with their closest taxon. However, isolate AT2015/10 showed 99.82 % sequence similarity with the top-hit taxon Laspinema thermale and it was observed that isolate AT2015/10 isolated from different habitat when compared to the genetically closest cyanobacterium Laspinema thermale. Thus, these sixteen cyanobacterial isolates could be described as novel taxa in the taxonomy of cyanobacteria. Euhalothece sp AT2016/13 isolated from Sambhar Lake was found to be a potent source of carotenoids whereas H. alcalis AT2015/9 and H. alcalis AT2015/9 were rich in total phycobiliproteins. D. tharense AT2015/7 and S. subsalsa AT2016/1 were reported to have maximum amount of phenolic contents and also exhibited significant radical scavenging activity in the water extract

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