A Study on the Life Time of the S3-State in the Filamentous Cyanobacterium Oscillatoria chalybea

G. H. Schmid, K. P. Bader, and R. Schulder Universität Bielefeld, Fakultät für Biologie, Lehrstuhl Zellphysiologie Postfach 100131, D-33501 Bielefeld, Bundesrepublik Deutschland Z. Naturforsch. 49c, 108-114 (1994); received July 26/October 11,1993 Filamentous Cyanobacterium, S-State, Metastable S3-State, Kok Model In the filamentous cyanobacterium Oscillatoria chalybea deactivation of the S-states start­ ing from steady-state conditions in which S0 = Sj = S2 = S3 = 25% reveals that S3 deactivates to a finite level of approx. 10%. This level is reached under normal conditions between 10-15 seconds. This quasi metastable S3 meets all requirements for S3 in that one flash eliminates this redox conditions to give S4 and therewith molecular oxygen. An analysis of the cyanobacterial S-state system in the 5-state Kok model shows that the S-state population in the dark adapted sample contains no contribution from S_x or a more reduced condition which under normal conditions is the case for Chlorella or higher plant chloroplasts. Hence under standard conditions, the Oscillatoria condition is a pure Kok-4-condition in which S0 is the most reduced state. Under these conditions S2 seems to deactivate to Sv and S3 to S2 and to a smaller extent to S0. In the presence of the ADRY-reagent Ant-2-p (2-(3-chloro-4-trifluoromethyl)-anilino-3,5-dinitrothiophene) introduced by Renger (Biochim. Biophys. Acta 256,428,1972), which is supposed to specifically act on the S3-state (and thereby on S2), not only the deactivation kinetic of S3 (and S2) is accelerated (hence the life time of the S3-state is shortened), but also the level of metastable S3 becomes practically zero. An analysis of the deactivation pattern shows that the agent changes the mode of deactivation of the entire system. Thus, it is seen that after deactivation of a sample in presence of this agent the dark population of S-states contains the more reduced redox condition S_r It looks as if in this condition S2 deactivates not only to Sx but also to an appreciable extent by two steps to S_v Another agent ABDAC (alkyl-benzyl-dimethyl-ammoniumchloride) seems to lengthen the lifetime of the S2 and S3 condition in this cyanobacterium by apparently acting on the mem­ brane condition.