Male-killing bacteria in a parasitic wasp.

A rod-shaped bacterium has been isolated that kills male eggs of the wasp Nasonia vitripennis, a pupal parasite of flies. Only some wasps of this species express this son-killer trait, and these wasps have bacterial infections in various organs. The bacterium was isolated from son-killer wasp tissue and from the hemolymph of fly pupae parasitized by wasps expressing the son-killer trait. Bacteria are apparently transferred to parasitized fly pupae during wasp oviposition, and developing wasp offspring are subsequently infected perorally. Sex-ratio distortion by microorganisms is found in a variety of plants and animals. The infectious peroral transmission of this trait variety of plants and animals. The infectious peroral transmission of this trait is in contrast to the typical pattern of cytoplasmic inheritance of sex-ratio distortion in these other systems.