Physiological responses of phormidium fragile to naphthalene

ABSTRACT

The cyanobacterium, Phormidium fragile, was grown in culture media containing different concentrations of naphthalene. Tests were carried out under conditions allowing relatively free evaporation and volatilization of the hydrocarbon [open system] and in closed system in which hydrocarbon loss was minimized [closed system]. Under the former condition, the various naphthalene concentrations invariably affected dry weight gain of the organism. On the other hand, under the closed system, the dry weight decreased significantly. Under both cultural conditions, the algal protein content decreased, while the nucleic acids content was slightly affected by the type of cultural system. The alga accumulated larger amounts of carbohydrates under closed than open systems. Under the latter condition, naphthalene insignificantly affected MDH and stimulated GOT activity. On the contrary, under the closed system, MDH activity was stimulated by naphthalene, whereas GOT activity was hardly affected. Under both conditions, nitrate reductase was insensitive to naphthalene supplementation, while GPT activity increased at low concentrations, then dropped. There was a continuous increase in the different photosynthetic pigments with increased naphthalene concentrations. In the meantime, the lipid content of the alga was much higher under closed than open systems