Ecophysiology of the estuarine cyanobacterium Lyngbya aestuarii to varying salinity in vitro

Abstract

Lyngbya aestuarii, one of the dominant cyanobacterium grows in different salinity gradients of Chilika lagoon. It was isolated in axenic culture and its ecophysiology with response to different concentrations of salinity was studied in vitro to understand its adaptation strategies in the changing salinities of the lagoon. Changes in morphological features of the organism were observed with salinity gradients higher than 28 g/L and lower than 14 g/L salinity. Increase in growth was accompanied by increase of chlorophyll-a, carotenoid and cell protein contents of the organism from 3.5 to 28 g/L. Cellular carbohydrate content was higher with increasing salinity of the medium up to 90 g/L. No detrimental effect on pigment synthesis and macromolecular content of the organism was observed at the salinity level ranging from 7 to 56 g/L salinity. Methanolic extract of L. aestuarii showed prominent absorption at 334 nm in the UV-B region of the spectrum due to mycosporine-like amino acid (MAA) and the quantity of MAA increased with increasing salinity. At 7 g/L salinity 150, 93, 58, 34 and 18 kDa proteins were up-regulated; however, at 14 g/L 37, 26 and 28 kDa proteins and in 0, 3.5 and 90 g/L 122, 32 and 20 kDa proteins were repressed; this shows similarities of salinity-induced protein modifications as observed in higher plants. Super oxide dismutase activity also increased in the cells grown at 56 g/L salinity. We conclude because of having these effective adaptation strategies, L. aestuarii cope very well with the changing salinity in different seasons and grows well in the different sectors of the lagoon.