PBP2b PARTICIPATES IN SHAPE DETERMINATION AND CONTROL OF CELL DIVISION IN STREPTOCOCCUS PNEUMONIAE

ALBARRACIN ORIO A; PIÑAS G; CORTES P; ECHENIQUE J

Tucuman

Congreso; SAIB; 2009

SAIB

Beta-Lactam resistance ( LR) in is due to mutations inpenicillin-binding proteins (PBPs) PBP1a, PBP2x, and PBP2b, enzymes involved in cell wall synthesis and division. We have previously described a relationship between pbp2b mutations and morphological alterations, growth retardation, a high fitness cost, unusual simultaneous septa and FtsZ delocalization. The clinical LR strains harboring these pbp2b mutations showed no morphological abnormalities, but in a laboratory strain, the association of pbp mutated genes in double and triple pbp mutants caused partial and complete compensatory effects on cell division and fitness. By optical microscopy, subpopulations of pbp2b cells showed bacillar and coccoid (as wild-type strain) shapes. However, by electron microscopy, these coccoid-shape cells exhibited different defects, suchas incomplete and atypical septumformation and positioning, intracellular structures and frequent asymmetrical divisions. The double pbp2b/2x mutant showed inner cell wall accumulation, but the triple pbp mutant compensated these morphological alterations. In addition, the localization pattern of the PBP2b*-GFPfusionproteininwild-type and pbp2bmutant cells was consistent with a cell cycle deregulation. These results suggested that PBP2b is involved in essential processes related to cell shape determinationandcell division.