The alteration of cell membrane of sulfate reducing bacteria in the presence of Mn(II) and Cd(II)

In this work, the effects of manganese and cadmium on the biosorption, cell membrane and growth of a sulfate reducing bacteria (SRB) strain were studied in detail. The strain of SRB used in this studied belongs to Salmonella named as Salmonella Daqing, which is isolated from Daqing oil field, China. Because of electrostatic attraction, Mn2+ and Cd2+ can be absorbed on the cell surface with negative charges. After biosorption of Mn2+ and Cd2+ on the cell surface, the morphological character of the cells changed, even some cells were almost completely deformed. The fluorescence polarization has shown a significant decrease in membrane fluidity and the increase of permeability of cell membrane. Ion analysis also revealed that permeability of cell membrane increased because of damage of cell membrane. Changes of the spectral profile of S. Daqing MF were also observed, suggesting the damages of surface groups on the cell membrane. Furthermore, low concentration of metal ions can promote growth of the bacteria, while high concentration has inhibitory effects on S. Daqing MF. The reason is attributed to the easier absorbability of nutrition due to the increased cell permeability.