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Journal of Bacteriology, June 2000, p. 3323-3330, Vol. 182, No. 12
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 (G435
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
R
and G435
W) and the third at a highly conserved leucine
(L361
S). 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.
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