Experimental Evolution of Bacteria with Guanidino Compounds

Research Project

Project/Area Number	60560109
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	発酵・醸造
Research Institution	Sinshu University
Principal Investigator	YORIFUJI Takamitsu Faculty of Agriculture, Shinshu University. Professor, 農学部, 教授 (70026425)
Project Period (FY)	1985 – 1986
Project Status	Completed (Fiscal Year 1986)
Budget Amount *help	¥2,000,000 (Direct Cost: ¥2,000,000) Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1985: ¥1,500,000 (Direct Cost: ¥1,500,000)
Keywords	Pseudomonas / mutants of / Evolution of taurocyamine metabolism / Guanidino compounds / bacterial metabolism of / Regulatory mutation and bacterial metabolism
Research Abstract	An experimental system for the bacterial evolution of metabolic ability, which involved some guanidino compounds and guanidinopropionate amidinohydrolase (GPH) of Pseudomonas aeruginosa was constructed. Taurocyamine was not utilized by the parent strain P. aeruginosa GB-4; it was slightly active as the substrate of GPH but did not induce the enzyme. Many mutants which can grow on the compound were isolated and strain M-6 was selected for the further analysis. In contrast to the parent strain, strain M-6 synthesized GPH when the cells were incubated with taurocyamin, guanidinoacetate, or guanidinobutyrate, as well as with guanidinopropionate, although the strain did not produce the enzyme constitutively. It was concluded that the specificity of the regulatory protein that controls the synthesis of GPH was altered in the strain and it allowed the organims to grow on taurocyamine. Similar mutants were isolated from Serratia marcescens which acquired the ability to grow on guanidinovalerate, and the change was also ascribed to the alteration of the specificity of a regualtory protein. Another system for experimental evolution was proposed on the basis of the substrate and inducer specificity of an enzyme which hydrolyzes a series of alkyl diguanidines. The noticeable finding obtained in this research project is that a point mutation at a regulatory gene for an enzyme which is involved in the degradation of an organic compound sometimes leads to the alteration of the inducer specificity, not to the constitutive enzyme synthesis. This type of mutation has rarely been observed heretofore, but is considered to be advantageous for the natural selection. The significance of this type of mutation in the evolution of bacterial metabolism will be substanciated by further investigations.