S. Yoshikawa et al., ISOLATION AND CHARACTERIZATION OF ZYGOSACCHAROMYCES-ROUXII MUTANTS DEFECTIVE IN PROTON PUMPOUT ACTIVITY AND SALT TOLERANCE, Journal of fermentation and bioengineering, 79(1), 1995, pp. 6-10
Two mutants defective in salt tolerance were identified among hygromyc
in B (HygB)-resistant mutants of Zygosaccharomyces rouxii. These mutan
ts showed different phenotypes in terms of sensitivity towards high co
ncentrations of glucose and KCl. Recovery of salt tolerance by the add
ition of KCl and CaCl2 or by lowering pH (pH 4.0) was different for th
e two mutants. Moreover, both mutants showed lowered plasma membrane (
PM-) ATPase activity and proton pumpout activity. They exhibited neith
er growth nor proton pumpout activity in a medium containing 5% NaCl.
The proton pumpout activity was inhibited by vanadate, an inhibitor of
PM-ATPase, only when cells were incubated in the presence of more tha
n 1% NaCl. Damage of the proton pumpout activity seems to be the reaso
n for the salt sensitivity of both mutants. We showed that it was esse
ntial for Z. rouxii cells to pump out protons under a high salt enviro
nment using mutants defective in this ability.