Circadian Rhythm of ATP Contents in Synechococcus RF-1

[[abstract]]In the cyanobacterium Synechococcus RF -1, A TP contents changed rhythmically in continuous white light during a 72-h observation period, after the culture had been entrained in three successive 12/12 h light/dark cycles. The increase and decrease in ATP contents corresponded to the light and dark period, respectively, of the L/D cycle treatment given previously. The rhythm had a period of about 24 h and was insensitive to temperature from 24?C to 35?C. When two cultures were previously entrained 12 h out of phase, the rhythms were also out of phase. These observations demonstrate that cellular A TP content in Synechococcus RF-I is controlled by the circadian clock.