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Cyanobacterial oxygenic photosynthesis transformed the early Earth's biosphere and resulted in complex aerobic life forms. During the course of evolution, cyanobacteria retained many genes that responded to specific environmental cues. Our study shows that microaerobic treatment did not significantly alter the functionality of photosystem II complex in Synechococcus sp. strain PCC 7002. Surprisingly, no changes in the induction levels of psbA genes, especially in D1' isoform, were recorded. This finding is important as signals an atypical behaviour of D1' isoform from Synechococcus sp. PCC 7002 to microaerobic stress as compared to other cyanobacterial strains. [ABSTRACT FROM AUTHOR]

Cyanobacteria, green algae and higher plants have highly conserved photosynthetic machinery. Cyanobacteria have a great plasticity and can be found in different environments, from Arctic zones to hot springs; they can be part of microbial mats. The hot spring near Ciocaia, in Bihor County has a range of different temperatures, from 65.5°C at the spring well, 60.5°C at 2 meters away from the spring well and between 32-38°C in the area where microbial mats are formed. In this study we showed changes in PSII function in mats grown at the location of the hot spring, comparative with microbial mats grown in laboratory conditions. We also showed a comparative study of some basic parameters of chlorophyll fluorescence. These results are very important to understand the functionality of photosystem II in the larger context of adaptation to environmental cues. [ABSTRACT FROM AUTHOR]

The D1 protein of Photosystem II (PSII), encoded by the psbA genes, is an indispensable component of oxygenic photosynthesis. Due to strongly oxidative chemistry of PSII water splitting, the D1 protein is prone to constant damage and requires its replacement by a new copy every 5 h under low light conditions and every 20 minutes under intense illumination, whereas most of the other PSII subunits remain ordinarily undamaged. In cyanobacteria the D1 protein is encoded by a psbA gene family, ranging from 1 to 6 members. The presence of multiple psbA genes encoding different D1 isoforms is an indication of their importance in regulatory mechanisms responsible for maintaining a functional PSII upon changing environmental conditions in natural habitats of cyanobacteria. Herewith, we present a comparative analysis of the protein sequences encoded by psbA gene family in model cyanobacteria strains with sequenced genomes, highlighting their characteristic features that give indication of their putative function. [ABSTRACT FROM AUTHOR]