Ultrastructural and Intracellular Chemical Changes of a Novel Halophilic Strain V430 of Staphylococcus saprophyticus under CaCl2 Stress

Observation of the ultrastructural and intracellular chemical changes of CaCl₂-tolerant strains is important both for understanding their adaptation mechanism under high salt stress and for providing theoretical basis of their application in treating high-CaCl₂ wastewaters. A novel strain V 430 isolated by us has been successfully used to decrease the chemical oxygen demand (COD) concentration of diosgenin wastewater from 20 g l⁻¹ to less than 0.5 g l⁻¹. For this study, strain V430 was incubated in culture media of different CaCl₂ concentrations (up to 9.0%). Strain V430 cells incubated in media of high CaCl₂ concentration excreted extracellular substances and accumulated intracellular Ca²⁺ and K⁺ and free amino acids. The levels of intracellular cations and free amino acids increased with increase in CaCl₂ concentration of the medium. The increase in total free amino acids was mostly due to accumulation of glutamic acid. The strain cells under 9.0% CaCl₂ stress took up K⁺ in a short time, while accumulation of Ca²⁺ proceeded over the whole growth process.