Autori: Nagwa Gamal Mohammady¹

Editorial: springer, journal of applied phycology, 17 (2), p.161-170, 2005.

Rezumat:

The marine eustigmatophycean microalga Nannochloropsis (Monallantus) salina Hibberd was grown for 8 days in cultures to which various amounts of the aqueous extract of diesel fuel oil was added and the subsequent behaviour of the stressed growing cells was studied. The results revealed so as to by increasing the concentration of the pollutant there was a decrease in growth as measured by optical density and the deteriorating was maximum and accounted for about 33% of control at the concentration of 100% aqueous pollutant. Spectrophotometric examination of cell viability (using Evan’s blue dye) indicated a negative significant effect of diesel (P ≤ 0.05, while r= -0.92). Infrared spectra showed a slight variation in the absorbance of the cellular composition of the contaminated cells towards the normalized. Proteome analysis (using sodium dodecyl sulfate polyacrylamide gel electrophoresis “SDS-PAGE”) indicated that cell protein profiles depended on the pollutant concentration. Some of the resultant bands were characteristic to the pollutant concentration applied, indicating a distinct effect of the pollutant on the proteome structure. Iodine and Toluidine blue dyes were applied using light microscopy for detect starch and mucilage respectively. The results indicated the presence of starch during all treatments, while the mucilage has been reduced. Transmission Electron Microscopy observations showed alterations to cell walls and membranes with different degrees of plasmolysis leading to gradual increases in cell volumes. However, the nucleus, the nucleolus and the pyrenoid remained unaffected. Similar results were obtained when the microalga was cultured for 25 days in the 100% aqueous diesel extract indicating that long term culture does not affect the degree of pollutant stress. Further, these cells recovered their normal appearance and characteristics within 2 days of being transferred to a diesel extract-free culture medium indicating that N. salina shows a high tolerance to aqueous diesel fuel pollution.

Cuvinte cheie: cell viability, growth, infrared analysis, light microscopy, mucilage, Nannochloropsis salina, proteome analysis, stress, transmission electron microscopy.