Acinetobacter baumannii CarO outer membrane proteins are involved in basic amino acids uptake

SÁNCHEZ RI; MORAN BARRIO J; VIALE AM

Paraná

Congreso; LIV Reunión Anual SAIB 2018; 2018

The family of outer membrane (OM) proteins CarO is restricted to the family Moraxellaceae, where Acinetobacter baumannii belongs. We previously described four polymorphic carO variants with the corresponding CarO proteins exhibiting distinctive properties such as differential migrations in gels, antigenicity, formation of oligomeric structures, and L-ornithine permeation abilities. To further characterize the different A. baumannii CarO variants we used A. baylyi ADP1 as model. For this purpose we constructed ADP1 recombinant cells harboring genetic replacements for each of the A. baumannii carO variants. We evaluated the physiology of the mutants concerning growth in rich and minimal medium, susceptibility to external aggressors, and CarO production. All of the replacement mutants showed similar growth rates comparable to that of the wild-type ADP1, comparable susceptibility to ionic detergents and NaCl stress, and same levels of CarO accumulation in the OM. Motility assays indicated that restitution of CarO to the OM restored the motility of the recombinants in semisolid medium. Nutrient utilization assays conducted in minimal media supplemented with different compounds, including amino acids, sugars, and different phenolic compounds, indicated differential growth of the mutants only on the basic amino acid arginine. Mutants carrying CarO variants III and IV were impeded to grow in arginine, while cells carrying variants I and II could grow similarly to wild-type cells. The overall results indicate that CarO participates in the selective uptake of basic amino acids and suggest roles in the interaction with abiotic and biotic surfaces.