Polyamines participate in numerous cellular processes and are required for normal
cell growth in Escherichia coli. In this study, we constructed a new polyamine-deficient
E. coli mutant and investigated the physiological function of polyamines during normal
aerobic growth conditions. We showed that the requirement for sulfur-containing, branched
chain, and aromatic amino acids, which was exhibited in the sodA sodB double mutant
faced with severe oxidative stress, was also true of the polyamine-deficient mutant
during normal aerobic cell growth. Sorbitol, sucrose, mannose, 1,2-dihydroxybenzene-3,5-disulfonic
acid (Tiron), an antioxidant that functions as an oxygen radical scavenger including
z.rad;O(2)(-), and thiamine partially relieved the cell growth defect caused by polyamine
depletion in a dose-dependent manner. As was the case for the cells treated with paraquat,
the mutant had an elongated shape compared with the polyamine-proficient wild type.
Decreased aeration also relieved the cell growth defect of the polyamine-deficient
mutant. Finally, we confirmed that chloromethyl-2('),7(')-dichlorofluorescin diacetate
(DCFH-DA), which is oxidized in a fluorescent product in the presence of various oxidants,
also fluoresce in the polyamine-deficient cells. These results showed that abnormal
growth of the polyamine-deficient E. coli mutant results partially from oxidative
stress-induced damage and the mutant thus exhibits the requirement for antioxidant
or specific nutritional amino acid during normal aerobic growth.