Mystery solved: The bacterial protein that kills male fruit flies

An endosymbiotic bacterium, Spiroplasma, specifically kills the males of its fruit-fly host (Drosophila). This has perplexed biologists since the 1950's, but EPFL scientists have now solved the mystery by identifying the gene behind this gender-specific killing. In the fifties, geneticists were faced with a mystery: when two strains of the same fruit fly species (Drosophila) crossed, they only produced female flies instead of the expected 50:50 sex ratio. At first, scientists thought that what lay behind this was a genetic mutation, but it was later discovered that the cause was a hidden bacterium, Spiroplasma poulsonii. Spiroplasma is an endosymbiotic bacterium that lives in the fruit fly's blood and is passed on to it offspring through the female's oocytes. This bacterium remains largely hidden from its host but induces a fascinating reproductive manipulation: the specific killing of male embryos. Male-killing Spiroplasma bacteria in the hemolymph of an adult Drosophila fruitfly.