Photosynthesis and photorespiration - modeling the essentials.
Cyanobacterial Respiration | SpringerLink
In summary, our analysis suggests that Synechocystis has a large number of AEF pathways involved to preserve optimal photosynthetic processes under environmental perturbation, such as Ci or light availability (photosynthetic robustness). The quantitative analysis of photosynthetic parameters exhibited by iJN678 allowed us to classify these AEF pathways based on (i) photosynthetic yield, (ii) net contribution to the ATP/NADPH ratio, (iii) mechanisms used for ATP/NADPH balancing and/or energy dissipation, (iv) dependency on O2 availability, and (v) LEF target components on which they acted (). This classification represents a valuable tool for better understanding how phototrophs might select among their large array of accessory photosynthetic pathways those that are best suited for efficient response to environmental perturbations.
Respiration in cyanobacteria can occur in the thylakoid membrane ..
The PQ oxidase CydBD and the terminal cytC oxidase CYO were identified as AEF pathways involved in a pseudocyclic electron flow (PCEF) around PSII (). Under LLS, the flow of electrons around PSII resulted in a PSI/PSII ratio of less than 1 but an optimal ATP/NADPH ratio (). The CYO and CydBD pathways could be classified as high and low photosynthetic-yield pathways, respectively, based on the calculated values similar to CEF pathways (). Under CLS, PCEF also enabled optimal growth by acting as an electron sink, indirectly consuming more than 53% of the available photons and preventing internal overreduction (). In agreement with our in silico data, genetic evidence showed that, in the absence of PSI or under high-light conditions, terminal oxidases in Synechocystis used PSII-generated electrons and provided extra ATP levels (, ).