BIO-ORANIC CHEMICAL REEARCH ON CELL SIGNALS IN BACTERIA

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1. Fruiting body formation in Myxococcus, Stigmatellaaurantiaca.Stingmolone is a fruiting body inducing factor secreted from the cells of Stigmatella aurantiaca when the cells are starved and irradiated with light. Two genes, RelA and csgA are thought to be involved in fruiting body formation in another Mkococcus in which any low molecular weight factor like stigmolone has not been known. In this study, we isolated homologs to these genes from S. aurantiaca and made the bacterial mutants using these genes. In RelA disrupted mutant, the productivity of stigmolone was lost. The ability to form fruiting body could not be recovered by addition of stigmobne. So, RelA should be involved in requirement of receptability as well as productivity of stigmolone. The gene, csgA promoted the synthesis of stigmolone The Mrna of the gene was induced by starvation but not by light irradiation.2. Plant-pathogen interaction of phytopathogenic bacteria.(1) Phytotoxin produced by Pseudomonas syringae pv. syringae.The gene cluster for synthesis of Phytotoxin in P. syringe pv. syringae was isolated and the gene was disrupted. In the cultured medium of the mutant bacterium, the toxin was not detected. When the mutant was applied to a susceptive plant, the growth of the bacterium was inhibited and the disease symptom was much diminished. Then the toxin should be involved in the pathogenecity of the bacterium.(2) Flagellins of Pseudomonas avenaeFlagellin of P. avenae is involved in induction of the hypersensitive reaction (HR) to rice in strain species specific manner. The bacterial genes from pathogenic and non-pathogenic strains were expressed in E. coli. Both of the expressed proteins could similarly elicit HR to rice cultured cells. So it is concluded that the specificity of the flagelns does not depend on the difference of the amino acid sequences.