The bacterium Xenorhabdus nematophila inhibits phospholipases A2 from insect,prokaryote, and vertebrate sources

The bacterium, Xenorhabdus nematophila, is a virulent insect pathogen. Part of its pathogenicity is due to impairing cellular immunity by blocking biosynthesis of eicosanoids, the major recognized signal transduction system in insect cellular immunity. X. nematophila inhibits the first step in eicosanoid biosynthesis, phospholipase A₂ (PLA₂). Here we report that the bacterium inhibits PLA₂ from two insect immune tissues, hemocytes and fat body, as well as PLA₂s selected to represent a wide range of organisms, including prokaryotes, insects, reptiles, and mammals. Our finding on a bacterial inhibitor of PLA₂ activity contributes new insight into the chemical ecology of microbe–host interactions, which usually involve actions rather than inhibitors of PLA₂s.