title: Isolation of conditionally putrescine-deficient mutants of Escherichia coli.
abstract: Mutants defective in the conversion of arginine to putrescine were found by screening clones from mutagenized cultures for inability to produce urea during growth in arginine-supplemented media. Two partially blocked mutants were isolated; one was deficient in arginine decarboxylase and the other was deficient in agmatine ureohydrolase. As predicted from the pattern of putrescine synthesis in Escherichia coli, these mutants were conditionally putrescine-deficient. When grown in either minimal or ornithine-supplemented media, conditions which lead to preferential utilization of the ornithine to putrescine pathway, the mutants had normal intracellular polyamine levels. However, when the mutants were placed in arginine-supplemented media, the level of intracellular putrescine was lowered markedly. Under conditions where intracellular putrescine was 1% of normal, the doubling time of the mutants was increased approximately 10%. The putrescine-deficient mutants had wild-type morphology, normal levels of protein and ribonucleic acid (RNA), and stringent amino acid control of RNA synthesis.
mesh_terms: D000588:Amines / Q000096:biosynthesis / Q000378:metabolism*; D001120:Arginine / Q000378:metabolism; D001426:Bacterial Proteins / Q000032:analysis; D002262:Carboxy-Lyases / Q000032:analysis; D003470:Culture Media; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification* / Q000378:metabolism; D005827:Genetics, Microbial; D009154:Mutation; D009952:Ornithine / Q000378:metabolism; D012329:RNA, Bacterial / Q000032:analysis; D014510:Urease / Q000032:analysis
chemical_list: D000588:Amines; D001426:Bacterial Proteins; D003470:Culture Media; D012329:RNA, Bacterial; D001120:Arginine; D009952:Ornithine; D014510:Urease; D002262:Carboxy-Lyases