Light has important roles, not only as a source for photosynthesis, but also as a stimulus for many developmental processes of photosynthetic organisms. Among them, light takes effects on whole life cycle of photosynthetic microorganisms, such as cyanobacteria and rhodobacteria. Photosynthetic bacteria have numerous and subtle ways of sensing and responding to light. Phototrophic bacteria display many photomovement phenomena such as phototaxis, photophobic response, and photokinesis to search optimal environment for photosynthesis. It has to be answered: what is a photoreceptor of these photoresponse, and how light signal is transduced to final responses? I am interested in understanding light signal transduction cascade related to photoresponses of photosynthetic bacteria.

My doctoral dissertation at Korea Advanced Institute of Science and Technology included elucidation and identification of the genes involved in photomovement of cyanobacterium Synechocystis sp. PCC 6803. I found one che gene cluster that is involved in phototaxis and another that is related with motility. In addition, many photoreceptor gene knockouts were constructed to find out which photoreceptors are involved in the photomovement of Synechocystis 6803. That project is still in progress in my laboratory in South Korea. Current projects in Bauer's lab include biochemical c haracterization of Rhodosprillum centenum novel phytochrome, Ppr, and in vivo function study of ppr gene using microarray experiment. A phytochrome- like protein Ppr in the purple photosynthetic bacterium R. centenum has a photoactive yellow protein domain at the amino-terminus. This domain contains the covalently attached blue light-absorbing chromophore, p-coumaric acid. In addition, Ppr includes a central domain homologous to phytochrome and a carboxyl-terminal histidine kinase domain. We don't have any evidence except Ppr is involved in regulating chalcone synthase gene expression. W e are still pursuing to find out in vivo function of ppr gene and the reason why Ppr is bleached by light and how does the bleaching affect the conformation of Ppr.