Acinetobacter baumannii Outer Membrane Protein A Modulates the Biogenesis of Outer Membrane Vesicles

Acinetobacter baumannii secretes outer membrane vesicles (OMVs) during both in vitro and in vivo growth, but the biogenesis mechanism by which A. baumannii produces OMVs remains undefined. Outer membrane protein A of A. baumannii (AbOmpA) is a major protein in the outer membrane and the C-terminus of AbOmpA interacts with diaminopimelate of peptidoglycan. This study investigated the role of AbOmpA in the biogenesis of A. baumannii OMVs. Quantitative and qualitative approaches were used to analyze OMV biogenesis in A. baumannii ATCC 19606(T) and an isogenic Delta AbOmpA mutant. OMV production was significantly increased in the Delta AbOmpA mutant compared to wild-type bacteria as demonstrated by quantitation of proteins and lipopolysaccharides (LPS) packaged in OMVs. LPS profiles prepared from OM Vs from wild-type bacteria and the Delta AbOmpA mutant had identical patterns, but proteomic analysis showed different protein constituents in OMVs from wild-type bacteria compared to the Delta AbOmpA mutant. In conclusion, AbOmpA influences OMV biogenesis by controlling OMV production and protein composition.