Studies on the signal transduction network in adaptive responses in microorganisms.

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The final goal of our research is to understand the signal transduction networks in a bacterial cell.We have focused on the signal transductions in the adaptation response system for phosphate starvation in Pseudomonas aeruginosa for two years and performedthe genetic analyzes of the Pi taxis and the phosphate regulon.The summary of research results is as follows :1.An constitutive alkaline phosphatase (AP) mutant, designated APC1, showed a constitutive phosphate (Pi) taxis.The result suggests the existence of a common negative regulator for the Pi regulon and the Pi taxis.1.A chromosomal phoB mutant still showed the inducible Pi taxis, indicating the Pi taxis is not regulated by the phoB gene unlike the Pi regulon.2.We cloned a 27-kb DNA fragment that complements the mutation of APC1.Genetic analyzes of the fragment revealed the negative regulator is the Pi specific transport channel complex.4.A 20-kb fragment was obtained by shot-gun cloning usibg a chemotaxis deficient mutant as a host strain.Two chemotaxis genes, cheY and cheZ were found on the fragment by genetic analyzes.