Interaction of the photosynthetic and respiratory electron transport chains producing slow O2 signals under flashing light in Synechocystis sp. PCC 6803

Abstract

We investigated the slow signal of apparent O2 release under brief light flashes by using mutants of Synechocystis sp. PCC 6803 which lacked CP43 and D1. The slow signal was present at higher amplitudes in the mutants. It was inhibited by starving the mutants of glucose (>90%), by 10 mM NaN3 (85%) and by boiling samples for 2 min (100%). In the mutants and in the wild-type, the slow signal was 95% inhibited by the combination of DBMIB (2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone) and HQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide). In the wild type, the addition of DCMU (3-(3,4-dichlorophenyl)-1,1-dimethylurea) or CCCP (carbonylcyanide m-chlorophenylhydrazone) completely inhibited photosynthetic O2 evolution, yet failed to inhibit the slow signal. We explain the kinetics of the wild-type signal as a positive deflection due to the inhibition of respiration by PS I activity, and a negative deflection due to the stimulation of respiration by electrons originating from PS II. We found no evidence of a 'meta-stable S3' in Synechocystis sp. PCC 6803 that could contribute to the slow signal of apparent O2 release. We present a calculation which involves only averaging, division and subtraction, that can remove the contribution of the slow signal from the true photosynthetic O2 signal and provide up to a 10-fold improved accuracy of the S-state models.

Improved 5-step modeling of the Photosystem II S-state mechanism in cyanobacteria

“…However, we see an oxygen consumption on the first and second flashes, no oxygen on the third, and then small amounts that are progressively increasing (Fig. PCC 6803 (Meunier et al 1995). The oxygen consumption is in agreement with the hypothesis that oxygen binding to Photosystem II is necessary before it can evolve oxygen (Bader et al 1987).…”

“…The principle is similar to that described by Miyao et al (1987), excepted that we used it with whole cells. Oxygen yields were deconvoluted from respiratory transients as described in Meunier et al (1995). PCC 6803 were centrifuged for 5 min on the electrode at 10000 rpm.…”

Contribution of Chloroflexus respiration to oxygen cycling in a hypersaline microbial mat from Lake Chiprana, Spain

“…Indeed, the light‐induced inhibition of the respiration can be alleviated by PMF‐dissipating uncouplers (Richaud et al ., 1986). The inhibitory effect of light on respiration is well documented for purple non‐sulfur bacteria (Melandri and Zannoni, 1978; McCarty and Ferguson, 1982), in which also nitrate respiration is inhibited by light (Sabaty et al ., 1993), in Halobacterium halobium (Oesterhelt and Krippahl, 1973), cyanobacteria (Imafuku and Katoh, 1976; Scherer and Boeger, 1982; Dominy and Williams, 1987; Meunier et al ., 1995), and for C. aurantiacus (Pierson and Castenholz, 1974; 1995). It should be noted that this tight coupling of photosynthesis and respiration may not necessarily occur in eukaryotic phototrophs, where the respiration and photosynthesis are located in different cell organelles (mitochondria and chloroplasts) (Imafuku and Katoh, 1976).…”

“…We argued that the observed inhibition of CLB respiration by NIR light is a consequence of the feedback mechanism between the photosynthetic and respiratory apparatus that are coupled to the PMF in the cell membrane. As this coupling is characteristic for all phototrophic prokaryotic cells, most notably for cyanobacteria (Imafuku and Katoh, 1976; Scherer and Boeger, 1982; Dominy and Williams, 1987; Meunier et al ., 1995), based on the parallel with anoxygenic phototrophs it is to be expected that the oxygenic photosynthesis induced by VIS light is accompanied by simultaneous inhibition of respiration in these microorganisms. As already discussed above for the NIR light, this may have profound consequences for the assessment of O 2 and carbon budgets in microbial communities, especially if methods based only on the measurements of total O 2 concentrations are employed.…”

Temporal Changes in State Transitions and Photosystem Organization in the Unicellular, Diazotrophic Cyanobacterium Cyanothece sp. ATCC 51142

“…11 5, 1997tier et al, 1987. In this manner, the oxidation of the PQ pool by PSI centers under flashing light produces respiratory O, transients (Boichenko et al, 1993;Meunier et al, 1995a), and could reopen PSII centers that were closed because of respiratory activity. In addition, PSI cyclic electron flow reduces the cellular need for respiration by generating ATP.…”