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Antimicrobial Agents and Chemotherapy, December 2006, p. 4062-4069, Vol. 50, No. 12
0066-4804/06/$08.00+0     doi:10.1128/AAC.00677-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Mutational Analysis of Class A and Class B Penicillin-Binding Proteins in Streptococcus gordonii{triangledown}

Marisa Haenni, Paul A. Majcherczyk, Jean-Luc Barblan, and Philippe Moreillon*

Department of Fundamental Microbiology, University of Lausanne, Switzerland

Received 2 June 2006/ Returned for modification 6 August 2006/ Accepted 15 September 2006

High-molecular-weight (HMW) penicillin-binding proteins (PBPs) are divided into class A and class B PBPs, which are bifunctional transpeptidases/transglycosylases and monofunctional transpeptidases, respectively. We determined the sequences for the HMW PBP genes of Streptococcus gordonii, a gingivo-dental commensal related to Streptococcus pneumoniae. Five HMW PBPs were identified, including three class A (PBPs 1A, 1B, and 2A) and two class B (PBPs 2B and 2X) PBPs, by homology with those of S. pneumoniae and by radiolabeling with [3H]penicillin. Single and double deletions of each of them were achieved by allelic replacement. All could be deleted, except for PBP 2X, which was essential. Morphological alterations occurred after deletion of PBP 1A (lozenge shape), PBP 2A (separation defect and chaining), and PBP 2B (aberrant septation and premature lysis) but not PBP 1B. The muropeptide cross-link patterns remained similar in all strains, indicating that cross-linkage for one missing PBP could be replaced by others. However, PBP 1A mutants presented shorter glycan chains (by 30%) and a relative decrease (25%) in one monomer stem peptide. Growth rate and viability under aeration, hyperosmolarity, and penicillin exposure were affected primarily in PBP 2B-deleted mutants. In contrast, chain-forming PBP 2A-deleted mutants withstood better aeration, probably because they formed clusters that impaired oxygen diffusion. Double deletion could be generated with any PBP combination and resulted in more-altered mutants. Thus, single deletion of four of the five HMW genes had a detectable effect on the bacterial morphology and/or physiology, and only PBP 1B seemed redundant a priori.

* Corresponding author. Mailing address: Department of Fundamental Microbiology, Quartier UNIL-Sorge, Biophore Building, CH-1015 Lausanne, Switzerland. Phone: 41.21.692.56.01/00. Fax: 41.21.692.56.05. E-mail: philippe.moreillon{at}unil.ch.

{triangledown} Published ahead of print on 25 September 2006.

Antimicrobial Agents and Chemotherapy, December 2006, p. 4062-4069, Vol. 50, No. 12
0066-4804/06/$08.00+0     doi:10.1128/AAC.00677-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Haenni, M., Moreillon, P. (2008). Fitness Cost and Impaired Survival in Penicillin-Resistant Streptococcus gordonii Isolates Selected in the Laboratory. Antimicrob. Agents Chemother. 52: 337-339 [Abstract] [Full Text]  
  • Morand, B., Muhlemann, K. (2007). Heteroresistance to penicillin in Streptococcus pneumoniae. Proc. Natl. Acad. Sci. USA 104: 14098-14103 [Abstract] [Full Text]  
  • Haenni, M., Moreillon, P., Lazarevic, V. (2007). Promoter and Transcription Analysis of Penicillin-Binding Protein Genes in Streptococcus gordonii. Antimicrob. Agents Chemother. 51: 2774-2783 [Abstract] [Full Text]  
  • Haenni, M., Moreillon, P. (2006). Mutations in Penicillin-Binding Protein (PBP) Genes and in Non-PBP Genes during Selection of Penicillin-Resistant Streptococcus gordonii. Antimicrob. Agents Chemother. 50: 4053-4061 [Abstract] [Full Text]  


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