Lipids are critical components of all cell membranes and important signalling compounds as part of the immune system. The host lipid composition plays a key role during infection and is defined by dietary intake, in addition to endogenous synthesis in the liver. Bacteria have evolved efficient means of scavenging host fatty acids to preserve energy. In Gram-negative bacteria, fatty acid acquisition is mediated by the outer membrane protein, FadL. Although FadL is a known virulence factor in many species, how pathogens decide when to make or take fatty acids during infection is poorly understood.
We have defined the niche-specific fatty acid acquisition capabilities in the critical human pathogen, Acinetobacter baumannii. Further, our work revealed the incorporation of host poly-unsaturated fatty acids (PUFAs) with antimicrobial potential in the microbial membrane. To define if increased dietary PUFAs can promote bacterial clearance, mice were subjected to diets high in polyunsaturated fat (15% fish oil), saturated fat (15% lard), or a diet with balanced lipids (5% canola oil). These analyses revealed that dietary intervention substantially altered the host lipid environment in unique niches and affected bacterial invasion. Importantly, this work identified that dietary lipids play a role in controlling dyslipidemia and lipid droplet formation in the liver during infection.
Collectively, this is the first niche-specific report on the making and taking of fatty acids during infection. Further, dietary intervention was shown to be a potential treatment strategy in combatting bacterial infection.