z-logo
open-access-imgOpen Access
Mutational Analysis of Class A and Class B Penicillin-Binding Proteins in Streptococcus gordonii
Author(s) -
Marisa Haenni,
Paul Majcherczyk,
Jean-Luc Barblan,
Philippe Moreillon
Publication year - 2006
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.00677-06
Subject(s) - penicillin binding proteins , streptococcus gordonii , biology , microbiology and biotechnology , mutant , streptococcus pneumoniae , peptidoglycan , penicillin , biochemistry , gene , streptococcaceae , antibiotics
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 ofStreptococcus gordonii , a gingivo-dental commensal related toStreptococcus 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 ofS. pneumoniae and by radiolabeling with [3 H]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.

The content you want is available to Zendy users.

Already have an account? Click here to sign in.
Having issues? You can contact us here