ENERGY DEPENDENCY ON SALT-RESISTANCE OF STAPHYLOCOCCUS-AUREUS - EFFECTS OF VARIOUS INHIBITORS ON GROWTH IN HIGH SALINITY CONDITION

Abstract

The barrier system against high environmental salinity is closely related to the salt-resistance of S. aureus. Cells grown on a medium with a high salt concentration were studied to clarify the energy dependency for the maintenance of intracellular univalent cation. Cells grown on nutrient broth with 10% NaCl were more sensitive to NaN3 than those grown only on nutrient broth. Anaerobic conditions demonstrated a more powerful growth inhibition on salt-tolerant cells than normal cells. Salt-tolerant cells apparently have a higher energy dependency than normal cells. The high sensitivity to uncouplers, such as DNP[dinitrophenol] and FCCP [carbonylcyanide-p-trifluoro methoxyphenylhydrazone] suggested an energy dependency probably related to respiration and not to anaerobic glycolysis. The intracellular Na+ contents of normal cells and salt tolerant cells were 12.0 and 152.9 mmol/kg wet weight, respectively, and the K+ content of salt tolerant cells (90.2 mmol/kg wet weight) was lower than that of normal cells (215.8 mmol/kg wet weight). Intracellular Na+ and K+ contents were strongly affected by the addition of various inhibitors. Measurements of intracellular univalent cation contents showed an adaptively developed barrier system in salt tolerant cells and an energy-dependent transport mechanisms for Na+ efflux in normal cells and for K+ influx in salt tolerant cells.