Point mutations in a peptidoglycan biosynthesis gene cause competence induction in Haemophilus influenzae

J Bacteriol. 2000 Jun;182(12):3323-30. doi: 10.1128/JB.182.12.3323-3330.2000.

Abstract

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 (G(435)-->R and G(435)-->W) and the third at a highly conserved leucine (L(361)-->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.

MeSH terms

  • Amino Acid Sequence
  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cell Membrane Permeability
  • Chromosome Mapping
  • DNA, Bacterial / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Gene Expression Regulation, Bacterial
  • Haemophilus influenzae / drug effects
  • Haemophilus influenzae / genetics*
  • Haemophilus influenzae / growth & development
  • Haemophilus influenzae / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Peptide Synthases / genetics*
  • Peptide Synthases / metabolism
  • Peptidoglycan / biosynthesis*
  • Point Mutation*
  • Transformation, Bacterial*

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • ComA protein, Bacteria
  • DNA, Bacterial
  • DNA-Binding Proteins
  • Membrane Proteins
  • Peptidoglycan
  • rec-2 protein, Haemophilus influenzae
  • Peptide Synthases
  • UDP-N-acetylmuramoylalanyl-D-glutamate-2,6-diaminopimelate ligase