DcaP-Family Porins are Required for Carboxylic Acid Utilization and Infection in Acinetobacter baumannii

<i>Acinetobacter baumannii</i> is a pathogen of concern and a leading cause of multidrug-resistant healthcare-associated infections. The <i>A. baumannii</i> outer membrane is a barrier to antimicrobials and host defenses but must also allow essential nutrients to permeate. Here, we investigate the functional importance of the putative DcaP-family outer membrane porins, which include a proposed vaccine target in <i>A. baumannii</i>. All <i>A. baumannii</i> genomes surveyed encode multiple DcaP family porins, which we classify in four classes based on protein sequence phylogeny (DcaP1-4). DcaP proteins encoded by species in other genera could not be mapped to these DcaP classes and phylogenetic analysis suggests DcaP1-4 proteins diversified within <i>Acinetobacter</i>. Phenotypic array assays and additional experiments show that DcaP3 was necessary for growth on multiple di- and tri-carboxylic acids as sole carbon sources, including citric acid and tricarballylic acid. Finally, a mutant lacking all DcaP proteins was attenuated in the liver and spleen in a mouse model of bloodstream infection and complemented by expression of DcaP3. These findings provide insight on how <i>A. baumannii</i> acquires nutrients through the outer membrane barrier and show DcaP3 is important during infection in specific host niches, validating its potential as a therapeutic target.