Fitness and FtsZ replacement restoration by incorporation of altered pbp genes in S pneumoniae

ALBARRACIN ORIO, A; PIÑAS G; CORTES P. AND ECHENIQUE, JR

Carlos Paz-Córdoba, Argentina

Congreso; XLIV Annual Meeting Argentine Society for Biochemistry and Molecular Biology (SAIB); 2008

SAIB

Beta-Lactam (bL) resistance in Streptococcus pneumoniae (orpneumococcus) is caused by mutations in penicillin-bindingproteins (PBPs), mainly PBP1a, PBP2x, and PBP2b, which areenzymes involved in cell wall synthesis and cell division cycle.Previously, we found that pbp2b mutants, obtained bytransforming pbp2b PCR products from bL-resistant isolates intoCP1015 strain, showed decrease fitness, morphologicalalterations. By using a fluorescent derivative of vancomycin (Fl-Van), we observed abnormal simultaneous parallel septal andequatorial staining. We also found by inmunofluorescencemicroscopy a FtsZ delocalization indicating cell division defects.Because no alterations were observed in the original bL- resistantstrains, we constructed double and triple mutants to analyze if pbpgenes association may compensate those alterations. The doublepbp2b/2x or pbp2b/1a mutants resulted only in a partially restoredmorphology. Double pbp mutants neither showed a complete FtsZplacement correction nor fitness restoration, whereas the triplepbp2b/2x/1a mutant was similar in morphology, fitness and Fl-Vanstaining to Cp1015, and it also showed a correct FtsZ localization.Our results suggest that acquisition by horizontal transfer ofpbp2x/pbp1a mutations have compensatory effects on fitness andcell division process, in addition to development of bL resistance.