Analysis of a cyanobacterium Synechocystis sp. PCC 6803 genome by application of chlorophyll fluorescence video-imaging system

Abstract

Since whole genome sequence of Synechocystis sp. PCC 6803 was determined in 1996, the function or interaction of genes has been targeted for elucidation. For the way to analyze the phenotype of gene disruptants exhaustively, we tried to apply the measurement of chlorophyll fluorescence intensity which reflects redox state of photosynthetic electron transport chain. In cyanobacteria, photosynthetic electron transport chain is not entirely separated from respiratory one, and other metabolisms including redox reactions seem to have indirect relation with photosynthetic electron transport chain. We thought that monitoring chlorophyll fluorescence enables us to analyze the effect of various gene disruptions. We utilized two-dimensional fluorescence video-imaging system that can determine time course change of chlorophyll fluorescence from multiple cyanobacterial patches individually. Introduction of this system enabled us to analyze many gene disruptants simultaneously. Using this system, we monitored the chlorophyll fluorescence kinetics of about 30 target gene disruptants. As a result, 4 gene disruptants showed altered primary peak position. These strains lack the gene coding glucose-6-p dehydrogenase or NADH dehydrogenase, so it was suggested that disruption of genes involved in glucose metabolism or respiration causes alteration of primary peak position. Nobel genes in these metabolisms may be characterized by the detection of similar fluorescence kinetics. We think that we can expect the function of novel gene through comparison of fluorescence kinetics with that in wild type strain. In parallel with these analyses, we prepared mutants made by transposon mutagenesis, and monitored their chlorophyll fluorescence kinetics.