Functions of the outer membrane protein CarO homolog in Acinetobacter baylyi

MUSSI, A.; RELLING, V.; RAVASI P; LIMANSKY A; VIALE, A.

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2007

SAIB

Resistance to the last generation of b-lactam carbapenem antibiotics in clinical strains of A. baumannii was associated with the loss of a 29 kDa OMP designated CarO (1). CarO was shown to serve channel functions for L-ornithine and L-arginine in this organism. Since CarO is a member of a family of OMPs restricted to the Moraxellaceae (1), we evaluated the function of an homolog present in the soil bacterium A. baylyi exhibiting 68% primary sequence identity. We thus generated a DcarO deletion mutant by genetic replacement, and found that the absence of this OMP resulted in a selectively impairment of the mutants to grow on L-arginine among all carbon sources tested. Moreover, A. baylyi DcarO mutants not only displayed increased resistance to carbapenems but also exhibited an outstanding ability to grow at high Na+ concentrations which were inhibitory to the wild type strain. Interestingly this effect was not observed in the case of similar K+ concentrations. These findings indicate CarO family members play roles in the specific permeation of basic amino acids. Moreover they also suggest that A. baylyi CarO, in particular, allows the selective permeation of Na+. (1) Mussi M.A., Limansky A.S., Viale A.M. (2005). Antimicrob. Agents Chemother. 49 (4): 1432-1440.