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

ALBARRACIN ORIO A; PIÑAS G; CORTES P; 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 (or pneumococcus) is caused by mutations in penicillin-binding proteins (PBPs), mainly PBP1a, PBP2x, and PBP2b, which are enzymes involved in cell wall synthesis and cell division cycle. Previously, we found that pbp2b mutants, obtained by transforming pbp2b PCR products from BL-resistant isolates into CP1015 strain, showed decrease fitness, morphological alterations. By using a fluorescent derivative of vancomycin (Fl- Van), we observed abnormal simultaneous parallel septal and equatorial staining. We also found by inmunofluorescence microscopy a FtsZ delocalization indicating cell division defects. Because no alterations were observed in the original BL- resistant strains, we constructed double and triple mutants to analyze if pbp genes association may compensate those alterations. The double pbp2b/2x or pbp2b/1a mutants resulted only in a partially restored morphology. Double pbp mutants neither showed a complete FtsZ placement correction nor fitness restoration, whereas the triple pbp2b/2x/1a mutant was similar in morphology, fitness and Fl-Van staining to Cp1015, and it also showed a correct FtsZ localization. Our results suggest that acquisition by horizontal transfer of pbp2x/pbp1a mutations have compensatory effects on fitness and cell division process, in addition to development of BL resistance.