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Infection and Immunity, September 2005, p. 5311-5318, Vol. 73, No. 9
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.9.5311-5318.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

Helicobacter hepaticus Hydrogenase Mutants Are Deficient in Hydrogen-Supported Amino Acid Uptake and in Causing Liver Lesions in A/J Mice

Nalini S. Mehta,1 Stephane Benoit,1 Jagannatha V. Mysore,2 Renato S. Sousa,2 and Robert J. Maier1*

Department of Microbiology,1 Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia 306022

Received 18 October 2004/ Returned for modification 30 November 2004/ Accepted 12 April 2005

Helicobacter hepaticus, a causative agent of chronic hepatitis and hepatocellular carcinoma in mice, expresses a nickel-containing hydrogen-oxidizing hydrogenase enzyme. Growth of a hyaB gene-targeted mutant was unaffected by the presence of hydrogen, unlike the wild-type strain, which showed an enhanced growth rate when supplied with H2. Hydrogenase activities in H. hepaticus were constitutive and not dependent on the inclusion of H2 during growth. Addition of nickel during growth significantly stimulated both urease (for wild-type and hyaB) and hydrogenase (for wild-type) activities. In a 5-h period, the extent of 14C-labeled amino acid uptake by the wild type was markedly enhanced in the presence of hydrogen and was >5-fold greater than that of the hyaB mutant strain. In the presence of H2, the short-term whole-cell amino acid uptake Vmax of the parent strain was about 2.2-fold greater than for the mutant, but the half-saturation affinity for amino acid transport was the same for the parent and mutant strain. The liver- and cecum-colonizing abilities of the strains was estimated by real-time PCR quantitation of the H. hepaticus-specific cytolethal distending toxin gene and showed similar animal colonization for the hyaB mutant and the wild type. However, at 21 weeks postinoculation, the livers from mice inoculated with wild type exhibited moderate lobular lymphoplasmacytic hepatitis with hepatocytic coagulative necrosis, but the hydrogenase mutants exhibited no histological evidence of lobular inflammation or necrosis.

* Corresponding author. Mailing address: Department of Microbiology, 815 Biological Sciences Building, University of Georgia, Athens, GA 30602. Phone: (706) 542-2323. Fax: (706) 542-2674. E-mail: rmaier{at}uga.edu.

Editor: J. N. Weiser

Infection and Immunity, September 2005, p. 5311-5318, Vol. 73, No. 9
0019-9567/05/$08.00+0     doi:10.1128/IAI.73.9.5311-5318.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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