Effects of Various Physico-chemical Parameters on Growth, Morphology and Physiology of a Thermophilic Cyanobacterium Fischerella thermalis (Schwabe) Gomont

Abstract

The growth as well as morphological and physiological features of thermophilic cyanobacteria vary greatly depending upon the physico-chemical factors prevailing in the water of hot springs. Effects of some physico-chemical parameters of water like-temperature, pH, nitrate and phosphate contents were observed on a thermophilic cyanobacterium Fischerella thermalis isolated from a hot water spring located at Panifala, Burdwan, West Bengal. Catalase activity under varying temperatures and light intensities was also studied in in vitro condition. Filaments incubated at 45o -55o C temperature, acidic (5.0-7.0) and highly alkaline (10.0) pH, high concentration (1.0-2.0 g/L) of NaNO3 and low (0-0.02 g/L) as well as high concentration (0.1 g/L) of K2 HPO4 showed various morphological abnormalities like shrinkage of cells, degradation of cellular contents, twisted and broken trichomes, discolouration of filaments, empty filaments. Such variations in physical and chemical factors also resulted in variations in protein, carbohydrate, chlorphyll-a and carotenoid contents. Heterocyst frequency and branching frequency was highest at 37o C temperature, 8.0-9.0 pH and 0.06 g/L of K2 HPO4 concentration. At increasingly high concentration of NaNO3 branching frequency increased but heterocyst frequency decreased. 37o C temperature, pH 8.0, 1.0 g/L NaNO3 and 0.06 g/L of K2 HPO4 concentration were found to be ideal for growth in in vitro condition. High light intensity (75 photons m-2 s-1) and low temperature (25o C) were observed to be responsible for increased catalase activity. This investigation will help to optimize the culture medium for in vitro production of biologically significant organisms like filamentous thermophilic cyanobacteria and throw light on experimental taxonomy.