Changes in Intracellular pH Are Not Correlated with the Circadian Rhythm of Neurospora.

Intracellular pH (pH(i)) was measured during the circadian cycle of Neurospora. Internal pH of Neurospora cultures in liquid medium was assayed by the 5,5-dimethyl-2,4-oxazolidinedione method and gave values for pH(i) which were similar to those previously obtained by other workers using pH-microelectrodes with agar-grown cultures. Cytoplasmic pH changed in liquid medium cultures, but these changes were not related to the circadian clock. Furthermore, treatments which raise or lower pH(i) do not phase-shift the circadian rhythm. These results indicate that pH(i) plays no specific role in regulating the circadian clock of Neurospora.