A photosynthetic organism which does not release oxygen is

A photosynthetic organism that does not release oxygen is a green sulphur bacterium.
These bacteria are a phylum of obligately anaerobic photoautotrophic bacteria that metabolize sulfur.
Green sulfur bacteria are nonmotile and capable of anoxygenic photosynthesis.
They live in anaerobic aquatic environments. In contrast to plants, green sulfur bacteria mainly use sulfide ions as electron donors. They are autotrophs that utilize the reverse tricarboxylic acid cycle to perform carbon fixation.