PHYSIOLOGICAL AND BIOCHEMICAL CHANGES IN ALGAL CULTURES OF CHLORELLA VULGARIS AND SYNECHOCYSTIS SALINA (MESOPHILIC AND ANTARCTIC ISOLATES) OCCURING AFTER TREATMENT WITH UV-B RADIATION

Dilyana Doneva,Juliana Ivanova,Lyudmila Kabaivanova

doi:10.32006/eeep.2017.1.7382

Abstract

Determination of biomass production and viability of algal cells of Chlorella vulgaris and Synechocystis salina exposed to UV-B radiation were carried out in this study together with comparison of the mesophilic and antarctic isolates of both investigated strains. Estimation of the content of the pigments: chlorophyll a, chlorophyll b, β-carotene, C-phycocyanin and allo-phycocyanin in algal cells exposed to UV-B radiation was also accomplished. The obtained results showed that the antarctic algae are more resistant to oxidative stress than their mesophilic counterparts. The antarctic isolates of Ch. vulgaris and S. salina compared with the mesophilic ones - up to 72 h showed tolerance to low exposures of radiation, expressed in a slight stimulation of growth and viability of the cells. Antarctic isolates also showed greater resistance to low doses of UV-B radiation manifested by stimulation of the synthesis of chlorophyll a and β-carotene. The registered increase in the amount of C- and allo-phycocyanin in antarctic isolates of S. salina showed that they had developed protective strategies against UV-B radiation by increasing the concentration of the phycobiliproteins. As a result of increased UV-B background, in antarctic isolates, stronger antioxidant defence mechanisms are triggered, which proved the possibility of using them as markers of oxidative stress.

Highlights

Algae are an extensive group of photosynthetic organisms distributed through a wide variety of habitats
UV-B radiation is a small component of the solar spectrum (
Biomass production and viability of algal cells exposed to UV-B radiation was followed, as well as the comparison between the antarctic and mesophilic isolates of Chlorella vulgaris (Fig. 1 A, B)

Summary

Introduction

Algae are an extensive group of photosynthetic organisms distributed through a wide variety of habitats. They are the main support of the entire life. Algae may develop numerous strategies to cope with UV radiation like multiple layered cell walls, absorbing compounds such as carotenoids, proteins and some reparing enzymes, that enable adaptation to environmental stress [2]. UV-B radiation is a small component of the solar spectrum (

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