Salient features of Protochlorophyta

Abstract

The Prochlorophytes are a varied group of photosynthetic prokaryotic organisms that belong to the cyanobacterial lineage, but they do not possess phycobilisomes as structures for the collection of light energy. Instead, the Prochlorophytes contain a light-harvesting mechanism that is made up of the pigments chlorophylls a and b, which are found in higher plants. In this overview, the antenna structures, photosynthetic characteristics, and evolutionary connections among these bacteria are discussed. The primary emphasis is placed on the part that photosynthesis plays in the environment in which these bacteria are found. The vast majority of the material that is now accessible comes from research conducted on Prochlorothrix, the model organism used to investigate this group in the laboratory. According to the results of our investigation, the thylakoid membrane in Prochloron and Prochlorothrix is arranged in a manner that is generally accepted by the scientific community. Because there have been no laboratory investigations carried out on Prochlorococcus, an abundant third Prochlorophyte, this species is not (yet) eligible for inclusion in the consensus. In general, we hypothesize that the structure of the light-harvesting complexes seen in Prochlorophytes is quite distinct from that of chloroplast systems, and that it is also very old in terms of evolutionary timescales. In both Prochlorothrix and Prochloron, the light-harvesting apparatus is thought to continue to retain a strong structural and functional relationship with Photosystem I. Photosystem In comparison to other photosynthetic systems, the donor and acceptor sides of the reaction center in Prochlorothrix have structural and functional features that are distinct from those of other photosynthetic systems. A demonstrated capacity for Photosystem I-dependent anoxygenic photosynthesis in Prochlorothrix may indicate that there is an increased dependence on cyclic photophosphorylation in these organisms. Speculation on the role that the photosynthetic apparatus plays in occupying, proliferating, and surviving in the ecological niches occupied by the Prochlorophytes has been based on a description of their natural habitats. It would seem that prochlorophytes thrive best in stable settings with a low light level, an adequate supply of nitrogen, and potentially the presence of necessary organic solutes.