Fitness and FTSZ placement restoration by incorporation of altered pbp genes in pneumococcus

ORIO AG, PIÑAS GE, CORTES PR, ECHENIQUE J

CARLOS PAZ

Encuentro; XLIV REUNION ANUAL SOCIEDAD ARGENTINA DE INVESTIGACION EN BIOQUIMICA Y BIOLOGIA MOLECULAR; 2008

SAIB

-Lactam ( L) 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 L-resistant isolates into CP1015 strain, showed decrease fitness, and morphological alterations. By using a fluorescent derivative of vancomycin (FlVan), 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 L- 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 L resistance