The present study aimed to evaluating the effect of chloramphenicol (CAP) and copper (CuSO4) on the cell ultra-structure of Scenedesmus sp. Three different concentrations of CuSO4 (10-3, 10-4, 10-5 M) and two of CAP (0.25 and 0.5%) were added to exponentially growing algal culture (107 cells ml-1) for 24 hrs. Cells treated with 10-3 M CuSO4 and 0.5% chloramphenicol which gave high amount of cell lyses were chosen for examination by electron microscopy. Transmission electron microscopy photographs of Scenedesmus cells treated with CuSO4 showed deformation of the chloroplasts, while numerous vesicles were observed in the cytoplasm. The threelaminar sheath (TLS) and the reticulate layer (RL) had no differences in comparison with control. On the other hand, tubular spikelets had no distinct shape compared with the control. The inner layer of cell wall (cellulose layer) showed shrinkage in thickness. Moreover, cells treated with 0.5% CAP showed that chloroplast thylakoids were reduced in size and number, disorganization, shrinkage in all protoplasmic components and increasing in the number of vacuoles and cellulose layer thickness. These results may help in understanding the effect of some toxins such as antibiotics and heavy metals on the cell structure of microalgae.
Key words: Antibiotics, Cell Ultrastructure, Heavy Metals, Microalgae, Scenedesmus