Acinetobacter baumannii is a Gram-negative cocco-bacillus newly emerging as a multidrug-resistant opportunistic pathogen. Although A. baumannii is considered to be one of the more threatening “superbugs” for healthcare systems worldwide, little is known about the factors contributing to its pathogenesis.  We have sequenced three new A. baumannii strains from Australian hospitals and indigenous sources to complement existing genomes encompassing strains from USA and Europe.  

I have utilized protein structure determination to enhance functional annotation of genomic island components within the Australian A. baumannii strains.  Two crystal structures have been solved and they identify factors involved in oxidative stress and lipopolysaccharide (LPS) biosynthesis.

The crystal structure of A. baumannii epimerase (D2) reveals an enzyme of the short-chain dehydrogenase/reductase (SDR) family. My structure shows two domains with an intertwined connectivity; the cofactor NADP-binding site is located in the larger Rossmann-fold domain, and a smaller C-terminal domain likely interacts with substrate. A close structure relative (FlaA1) occurs in Helicobacter pylori (rmsd 1.7 Å) and is implicated in the biosynthesis of both LPS and flagella.

In A. baumannii D1279779, the D2 enzyme is encoded within a genomic island, which has been only seen in one other A. baumannii strain.  This island additionally contains a cluster of six other genes encoding the biosynthetic pathway of O-antigen, the third domain of LPS.