Genetic engineering of Enterobacter aerogenes with the Vitreoscilla hemoglobin gene: cell growth, survival, and antioxidant enzyme status under oxidative stress.

Hemoglobins in unicellular organisms, like the one here in the bacterium Vitreoscilla, have greater chemical reactivity than their homologues in multicellular organisms. They can catalyze redox reactions and may protect cells against oxidative stress. The ability of Vitreoscilla hemoglobin to complement deficiencies of terminal cytochrome oxidases in Escherichia coli also suggests that this hemoglobin can receive electrons during respiration. In this study, a recombinant strain of Enterobacter aerogenes engineered to produce the Vitreoscilla Hb was investigated with regard to its susceptibility to oxidative stress. The culture response to oxidative stress produced by exogenously applied hydrogen peroxide was characterized in terms of cell growth, survival and the activities of two key antioxidant enzymes (catalase and superoxide dismutase). The influence of the physiological state of the cells and different media upon these culture dynamics was determined. Results showed that the hemoglobin-expressing strain is quite distinct in terms of growth/survival properties and activity of antioxidant enzymes from that of non-hemoglobin counterparts.