Growth Response and Heat Shock Protein (Hsp) Expression in Chlorella vulgaris Exposure to Elevated Temperatures

The present paper deals with the impact of various sublethal levels of temperature (26, 31, 33, 36, 39, 42 and 45o C) on growth and heat shock protein (Hsp) expression in freshwater green alga Chlorella vulgaris. Impact of select levels of temperature on growth rate (based on optical density), population count, chlorophyll-a and biomass, of the alga was evaluated in artificial growth medium for a period of 15 days. To determine the induction of Hsp in the alga, it was exposed to select temperature levels for 3 hrs. and further kept for 6 hrs at culturing conditions at 26o C. Induction of Hsp was confirmed by immuno detection followed by SDSPolyacrylamide gel electrophoresis. The select growth parameters of the alga were reduced drastically at 39, 42 & 45o C. Temperatures below 39o C may be considered as the limit of safe exposure for thermal stress of the alga. The Hsp 70 expression was also observed only at 39o C