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Journal of Bacteriology, December 2000, p. 6874-6883, Vol. 182, No. 24
Department of Medical Microbiology and
Parasitology, University of Georgia, Athens, Georgia 30602
Received 12 June 2000/Accepted 2 October 2000
Pasteurella multocida is a mucosal pathogen that
colonizes the respiratory system of susceptible hosts. Most isolates of
P. multocida produce sialidase activity, which may
contribute to colonization of the respiratory tract or the production
of lesions in an active infection. We have cloned and sequenced a
sialidase gene, nanH, from a fowl cholera isolate of
P. multocida. Sequence analysis of NanH revealed that it
exhibited significant amino acid sequence homology with many microbial
sialidases. Insertional inactivation of nanH resulted in a
mutant strain that was not deficient in sialidase production. However,
this mutant exhibited reduced enzyme activity and growth rate on 2-3'
sialyl lactose compared to the wild type. Subsequently, we demonstrated
the presence of two sialidases by cloning another sialidase gene that
differed from nanH in DNA sequence and substrate
specificity. NanB demonstrated activity on both 2-3' and 2-6' sialyl
lactose, while NanH demonstrated activity only on 2-3' sialyl lactose.
Neither enzyme liberated sialic acid from colominic acid (2-8' sialyl
lactose). Recombinant E. coli containing the sialidase
genes were able to utilize several sialoconjugants when they
were provided as sole carbon sources in minimal medium. These
data suggest that sialidases have a nutritional function and may
contribute to the ability of P. multocida to colonize and
persist on vertebrate mucosal surfaces.
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Cloning and Characterization of Sialidases with
2-6' and 2-3' Sialyl Lactose Specificity from Pasteurella
multocida
*
Corresponding author. Mailing address: Department of
Medical Microbiology and Parasitology, University of Georgia, Athens, GA 30602. Phone: (706) 542-5778. Fax: (706) 542-5771. E-mail: leem{at}calc.vet.uga.edu.
In memory of Rick Rimler, who knew so much about P. multocida.
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