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Journal of Bacteriology, September 2003, p. 5555-5562, Vol. 185, No. 18
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.18.5555-5562.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Glutathione and Catalase Provide Overlapping Defenses for Protection against Respiration-Generated Hydrogen Peroxide in Haemophilus influenzae

Bjorn Vergauwen, Frederik Pauwels, and Jozef J. Van Beeumen*

Laboratory for Protein Biochemistry and Protein Engineering, Ghent University, 9000 Ghent, Belgium

Received 6 February 2003/ Accepted 27 June 2003

Glutathione is an abundant and ubiquitous low-molecular-weight thiol that may play a role in many cellular processes, including protection against the deleterious effects of reactive oxygen species. We address here the role of glutathione in protection against hydrogen peroxide (H2O2) in Haemophilus influenzae and show that glutathione and catalase provide overlapping defense systems. H. influenzae is naturally glutathione deficient and imports glutathione from the growth medium. Mutant H. influenzae lacking catalase and cultured in glutathione-deficient minimal medium is completely devoid of H2O2 scavenging activity and, accordingly, substantial amounts of H2O2 accumulate in the growth medium. H. influenzae generates H2O2 at rates similar to those reported for Escherichia coli, but the toxicity of this harmful metabolite is averted by glutathione-based H2O2 removal, which appears to be the primary system for protection against H2O2 endogenously generated during aerobic respiration. When H2O2 concentrations exceed low micromolar levels, the hktE gene-encoded catalase becomes the predominant scavenger. The requirement for glutathione in protection against oxidative stress is analogous to that in higher and lower eukaryotes but is unlike the situation in other bacteria in which glutathione is dispensable for aerobic growth during both normal and oxidative stress conditions.


* Corresponding author. Mailing address: Laboratory of Protein Biochemistry and Protein Engineering, Ghent University, 9000 Ghent, Belgium. Phone: 32(0)9-264-51-27. Fax: 32(0)9-264-53-38. E-mail: Jozef.vanbeeumen{at}rug.ac.be.


Journal of Bacteriology, September 2003, p. 5555-5562, Vol. 185, No. 18
0021-9193/03/$08.00+0     DOI: 10.1128/JB.185.18.5555-5562.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.




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