Intracellular expression of Vitreoscilla hemoglobin alters Escherichia coli energy metabolism under oxygen‐limited conditions

Abstract

An earlier stoichiometric analysis of oxygen‐limited metabolism of Escherichia coli expressing cloned Vitreoscilla hemoglobin (VHb) suggested improved efficiency of ATP production relative to wild‐type controls [Khosla, C., Curtis, J. E., DeModena, J., Rinas, J. & Bailey, J. E. (1990) Bio‐Technol. 8, 849–853]. This hypothesis has been further examined by determining several energetic parameters of different VHb‐expressing E. coli (VHb+) strains relative to controls not expressing VHb (VHb–). The H+/O ratio, the transmembrane ΔpH, and the ATP content of VHb+ constructs are 1.5, 1.6 and 2 times, respectively, corresponding values in VHb– controls. VHb was expressed using a low‐copy‐number vector in E. coli mutant strains lacking cytochrome o, cytochrome d, or both terminal oxidases; significant growth enhancement due to VHb expression was observed only in the strain having functional cytochrome o and lacking cytochrome d. All of these data obtained using different E. coli strains are consistent with a model of VHb action that hypothesizes enhancement by VHb of activity of the lower oxygen‐affinity, higher proton‐pumping‐efficiency cytochrome o terminal oxidase under oxygen‐limited growth conditions.

Bacterial Hemoglobin gene (vgb) Transformed into Escherichia coli enhances Lead-Uptake and Minimizes it’s Adsorption

“…1, 2, 3 and 4). The changes in growth patterns and lead utilization by transformed cells could be due to direct effects of bacterial hemoglobin (VHb) or more subtlety and indirect effects of (VHb) on cell metabolism (De Mondena et al, 1993;Kallio et al, 1994;Khosla and Bailey, 1988;Khosravi et al, 1990).…”

“…As mentioned above, the genetically engineered bacteria have been produced to enhance their ability to grow, survive and thrive under extreme conditions. Therefore they can metabolize target chemicals compounds under these condition (Khosravi et al, 1990;Mains and Kappas, 1977;De Mondena et al, 1993;Kallio et al, 1994;Khosla and Bailey, 1988;Moat and Foster, 1988;Dressler et al, 1991). (2): To determine Pb uptake, biosorption and adsorption in both strains.…”

Mitochondrial Respiration and Hemoglobin Gene Expression in Barley Aleurone Tissue

“…There are several possible roles for Hb under hypoxic conditions: (a) it may serve as an O, carrier, like myoglobin (Wittenberg and Wittenberg, 1990), to allow mitochondrial respiration to continue during early anoxia; (b) it may act as an electron-transfer protein, as has been suggested for a flavohemoglobin from Esckerickia coli (Cooper et al, 1994) and the Vitreoscilla Hb (Chen et al, 1994;Kallio et al, 1994); and (c) it may function as a sensor to regulate expression of other genes, as has been shown for the heme protein FixL of Xkizobium meliloti (Gilles-Gonzalez and Gonzalez, 1993;Gilles-Gonzalez et al, 1994).…”

Expression of Vitreoscilla hemoglobin in Gordonia amarae enhances biosurfactant production

“…Although continuous oxygen monitoring was not practical for these shake flask cultures (and those described in the following section), rough adjustment of culture oxygen levels can be obtained by variation in shaking speed and culture volume to vessel volume ratio [6,16].…”

“…These include enhancement of antibiotic production in fungi [9], tissue plasminogen activator production in mammalian cells [31], and growth in plants and plant cell cultures [11,14]. There is evidence that the beneficial effects in bacteria are the result of direct interaction of VHb with the terminal respiratory oxidase, delivering oxygen to it to enhance oxidative phosphorylation and thus the production of ATP [16,30,32]. In the case of bioremediation enhancement, a direct delivery of oxygen by VHb to oxygenases which degrade aromatics may occur [20,21].…”