Effect of PBP mutations on cell morphology and growth rate in Streptococcus pneumoniae

ALBARRACÍN ORIO A., CORTES, P., PIÑAS G. Y ECHENIQUE, J.

MAR DEL PLATA

Encuentro; XLIII REUNION ANUAL SOCIEDAD ARGENTINA DE INVESTIGACION EN BIOQUIMICA Y BIOLOGIA MOLECULAR; 2007

SAIB

BETA-Lactam ( BL) resistance in is caused by mutations in penicillin-binding proteins (PBPs), mainly PBP1a, PBP2x, and PBP2b, which are enzymes involved in cell wall synthesis. Here, we assessed the impact of mutations on cell shape and growth rate. In addition, we used a fluorescent derivative of vancomycin (Fl-Van) as a probe for nascent peptidoglycan synthesis to evaluate the septal and equatorial pattern by fluorescence microscopy. The genes from L-resistant isolates were transformed into Cp1015, and the transformants were analyzed. All mutants showed growth retardation, morphological alterations and simultaneous parallel septal and equatorial staining by Fl-Van, but no such differences could be detected in or mutants. Because no alterations were observed in the original L- resistant strains, we constructed double and triple mutants to analyze if genes association may compensate growth rates and cell shape alterations in the mutants. The double or mutants resulted only in a partially restored morphology whereas the triple mutant was similar in morphology, growth rate and Fl-Van staining to Cp1015. Our results suggest that acquisition of mutations by horizontal transfer have compensatory effects on growth and shape alterations, in addition to development of BL resistance