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Journal of Bacteriology, June 2000, p. 3323-3330, Vol. 182, No. 12
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

Point Mutations in a Peptidoglycan Biosynthesis Gene Cause Competence Induction in Haemophilus influenzae

Caixia Ma and Rosemary J. Redfield*

Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada

Received 3 December 1999/Accepted 21 March 2000

We have identified three new Haemophilus influenzae mutations causing cells to exhibit extreme hypercompetence at all stages of growth. The mutations are in murE, which encodes the meso-diaminopimelate-adding enzyme of peptidoglycan synthesis. All are point mutations causing nonconservative amino acid substitutions, two at a poorly conserved residue (G435right-arrowR and G435right-arrowW) and the third at a highly conserved leucine (L361right-arrowS). The mutant strains have very similar phenotypes and do not exhibit any defects in cell growth, permeability, or sensitivity to peptidoglycan antibiotics. Cells retain the normal specificity of DNA uptake for the H. influenzae uptake signal sequence. The mutations do not bypass genes known to be needed for competence induction but do dramatically increase expression of genes required for the normal pathway of DNA uptake. We conclude that the mutations do not act by increasing cell permeability but by causing induction of the normal competence pathway via a previously unsuspected signal.


* Corresponding author. Mailing address: Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, British Columbia, V6T 1Z4, Canada. Phone: (604) 822-3744. Fax: (604) 822-2416. E-mail: redfield{at}unixg.ubc.ca.


Journal of Bacteriology, June 2000, p. 3323-3330, Vol. 182, No. 12
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.



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