Influence of salts and pH on the growth as well as NADH oxidase of the halotolerant bacterium A505

Abstract

Growth yield of the halotolerant bacterium A505 was increased by the supplement of Na+, K+, or Rb+ into the culture media with pH 7.5, and inhibited by Li+ or Cs+. In the presence of less than 0.1 M NaCl or KCl alkaline growth media, pH 9.2 to 9.7, afforded optimal growth of this strain. Intracellular ion content of this microbe changed reflecting on the Na+ or K+ concentration in the media, although it tended to accumulate K+ and extrude Na+ in the media without NaCl supplemented. A 1.2 to 1.4-fold stimulation of in vitro NADH oxidase activity was obtained by supplement of salts, except for LiCl. The rate of NADH oxidation in the absence of salts correlated with the pH and showed clear maxima at pH about 8, irrespective of growth conditions. In the presence of 0.5 M NaCl or KCl, on the other hand, pH dependence was less significant and showed only a flat maximum at pH around 7. Effects of anions on NADH oxidase were realized following the lyotropic series: SO 4 2- >F->CH3COO->Cl->I->SCN-, aside from NO 3 - , which exhibited the largest stimulation on enzyme activity in all the anions examined.