Pathogenic bacterial infections in Drosophila melanogaster parents shape offspring susceptibility and resistance to infections.

Transgenerational effects can determine offspring fitness when parents and offspring experience similar stressful conditions. A variety of biotic and abiotic stressors can induce such transgenerational effects, including pathogenic infections. We investigated whether infecting Drosophila melanogaster fruit flies with live, pathogenic bacteria improves offspring survival and disease resistance. We have demonstrated that infecting fly parents with two separate and distinct bacterial pathogens enhances the offspring's capacity to survive a homologous infection challenge (where parents and offspring are infected with the same bacteria) and a subset of heterologous infections (where parents and offspring are infected with different bacteria). Offspring of infected parents also exhibit increased capacity to prevent systemic pathogen proliferation, indicating increased disease resistance. Additional observations suggest that this improved survival and disease resistance are due to plastic phenotypic changes. Interestingly, parental infection does not compromise offspring reproductive output, either in the presence or absence of infection. This suggests that transgenerational effects of parental infection in fruit flies are limited only to offspring survival, and the increased disease resistance does not come at a (measurable) cost of offspring reproductive output.