Culturable cyanobacteria from some selected water bodies located in the major climatic zones of Sri Lanka

Abstract

Cyanobacteria are oxygenic photosynthetic prokaryotes with a wide morphological diversity with some members capable of fixing atmospheric N2. This paper reports on the taxa isolated and cultured from water in selected reservoirs in the Dry, Intermediate and Wet zones of Sri Lanka with the potential of utilizing them for biofuel and other industries including cosmetics. Water samples were concentrated by filtering through plankton net and re-suspended in 50 mL of either in respective reservoir water samples or in distilled water. Aliquots of these were cultured in blue green 11 (BG 11) and GO (same as BG11 media but N-free) media. Cultures were maintained under 2,000 lux light intensity with shaking at 200 rpm. A total of 64 cyanobacterial cultures, isolated by repeated sub-culturing in liquid and agar media, were observed under a light microscope for identification. While 16 different taxa were isolated from the Dry Zone, 12 and 5 taxa were isolated from the Wet and Intermediate zones, respectively. The frequency of isolating Oscillatoria sp. was high (10 reservoirs) followed by Microcoleus sp. and Microcystis sp. (each from 6 reservoirs). A strong positive correlation was recorded between cyanobacterial occurrences with abiotic properties such as water temperature, pH and secchi depth (turbidity). Samples prepared in water from respective reservoirs gave faster growth during culturing than those prepared in distilled water. The occurrence, availability and culturability of the isolates obtained in the present study will be useful in the development of value-added cyanobacterial products and cyanobacteria-based industries including biofuel.

Keywords

• culturable cyanobacteria, fresh water reservoirs, growth conditions, climatic zones of sri lanka