Antioxidant Status, alpha-Amylase Production, Growth, and Survival of Hemoglobin Bearing Escherichia coli Exposed to Hypochlorous Acid¹

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S. Aydin

Department of Biochemistry and Clinical Biochemistry, Firat University, Faculty of Medicine, 23119 Elazig, Turkey; fax: +90-424-237-9138; E-mail: saydin1@hotmail.com

¹This work was presented as a poster at the HUPO 4th Annual World Congress, August 28 to September 1, 2005, Munich, Germany.

Received June 28, 2005; Revision received August 23, 2005

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In the present work, two matched strains of E. coli that bear a recombinant R-amylase gene (MK57) or the R-amylase gene and vgb (MK79-hemoglobin expressing strain) were exposed to HOCl. In these cells, glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), alpha-amylase production, growth and lethality were assessed in the presence and absence of HOCl. It was observed that the hemoglobin makes cells highly susceptible to killing by HOCl. The maximum survival for both strains was with stationary phase cells at any concentration of HOCl. Both strains grown in the presence of 0.0125-0.075 mg/liter HOCl showed a substantial increase in SOD activity and GSH level, with MK79 being the most increased strain in this respect, while the level of CAT activity was decreased in a dose depended manner. Growth of MK57 and MK79 strains decreased as HOCl concentration increased. However, HOCl at concentration above zero enhanced alpha-amylase production (about 2-fold) in both MK79 and MK57. Furthermore, total amylase production (at all HOCl concentrations) by MK79 was always greater than that by MK57. The results indicate that except for survival, the hemoglobin helps cells to grow better and produces more recombinant products and activates general defense systems more in response to oxidative stress when compared with the non-hemoglobin-containing counterpart.

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KEY WORDS: Escherichia coli, Vitreoscilla hemoglobin, hypochlorous acid, oxidative stress, SOD, catalase, glutathione, alpha-amylase

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