Individual cells of Saccharomyces cerevisiae and Zygosaccharomyces bailii exhibit different short-term intracellular pH responses to acetic acid

The effects of perfusion with 2.7 and 26 mM undissociated acetic acid in th e absence or presence of glucose on short-term intracellular pH (pH(i)) cha nges in individual Saccharomyces cerevisiae and Zygosaccharomyces bailii ce lls were studied using fluorescence-ratio-imaging microscopy and a perfusio n system. In the S. cerevisiae cells, perfusion with acetic acid induced st rong short-term pH, responses, which were dependent on the undissociated ac etic acid concentration and the presence of glucose in the perfusion soluti ons. In the Z. bailii cells, perfusion with acetic acid induced only very w eak shortterm pHi responses, which were neither dependent on the undissocia ted acetic acid concentration nor on the presence of glucose in the perfusi on solutions. These results clearly show that Z. bailii is more resistant t han S. cerevisiae to short-term pHi changes caused by acetic acid.