Acinetobacter baumannii Employs a Rare Fatty Acid Desaturase for Niche-Specific Host Adaptation

Acinetobacter baumannii is a hospital-associated pathogen with unique fatty acid homeostasis features. This includes a reliance on desaturases for proliferation, due to an inability to generate unsaturated fatty acids during the synthesis cycles. However, there are various unexplained gaps in A. baumannii fatty acid homeostasis, such as the desaturation of de novo synthesized fatty acids. We identified a conserved desaturase (DesC) with a rare structural feature that may have roles in coordinating fatty acids with acyl carrier protein conjugants. We showed that DesC can generate fatty acids with cis double bonds in the delta-9 position. Profiling of A. baumannii fatty acids and mRNA transcripts emphasized its significance during fatty acid synthesis. DesC was found to be most critical in mouse niches where A. baumannii relies on fatty acid synthesis. This work has contributed to our understanding of core metabolic features that are key to the disease potential of A. baumannii.