BIO-ORANIC CHEMICAL REEARCH ON CELL SIGNALS IN BACTERIA

1. 粘球菌的子实体形成。黄毒刺酮是金柱头草细胞在饥饿和光照条件下分泌的一种子实体诱导因子。RelA和csgA这两个基因被认为与另一种Mkococcus的子实体形成有关，而在这种Mkococcus中还没有发现任何低分子量因子，如甾体酮。在本研究中，我们从金黄色葡萄球菌中分离出这些基因的同源物，并利用这些基因制备了细菌突变体。在RelA突变体中，甾酮的产量丧失。添加柱头草不能恢复形成子实体的能力。因此，RelA应涉及到甾酮的可接受性和生产效率的要求。基因csgA促进了甾酮的合成，该基因的Mrna受饥饿诱导，而不受光照诱导。植物致病菌的植物-病原体相互作用。(1)丁香假单胞菌产生的植物毒素。两。针状芽孢杆菌合成植物毒素的基因簇。分离了丁香属植物，并对该基因进行了破坏。在突变菌的培养基中，未检测到毒素。当将该突变体施用于易感植株时，细菌的生长受到抑制，病害症状大大减轻。那么毒素应该与细菌的致病性有关。(2)绿假单胞菌的鞭毛蛋白绿假单胞菌的鞭毛蛋白以菌种特异性的方式参与水稻的超敏反应（HR）诱导。致病性菌株和非致病性菌株的基因均在大肠杆菌中表达。这两种表达的蛋白对水稻培养细胞的诱导作用相似。因此，鞭毛蛋白的特异性并不取决于氨基酸序列的不同。

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.