REGULATION OF ESCHERICHIA-COLI SUPEROXIDE-DISMUTASE GENES (SODA AND SODB) BY OXYGEN

Two types of superoxide dismutase genes, sodA and sodB, were fused to beta-galactosidase gene (lacZ), in order to quantitatively study the effect of oxygen concentration on the gene expression of sodA and sodB. beta-Galactosidase activity derived from the sodA-lacZ fusion was induced by shifting from anaerobic condition to aerobic condition. Maximum activity (9.4 X 10(3) U/OD660) was observed when oxygen partial pressure was. 0.6 atm. On the contrary, gene expression level for the sodB-lacZ gene fusion was about two times higher during anaerobic condition than that during aerobic condition. From these results it was concluded that oxygen positively affected the gene expression of sodA and negatively affected the gene expression of sodB. An inducible expression vector using the sodA regulatory region was also constructed.