Spiroplasmas (q.v.) responsible for male-specific lethality in certain Drosophila species. SROs are transmitted in the ooplasm, and they kill male embryos. The Y chromosome is not associated with SRO-induced male lethality, and therefore only embryos with two X chromosomes can withstand the infection. Sex ratio spiroplasmas are referred to as sex ratio spirochaetes in the earlier literature. Spiroplasma poulsonii, a sex ratio spiroplasma of Drosophila willistoni, has been successfully cultivated on a complex, cell-free medium. Its genome contains 2.04 × 106 bp of DNA.
Subjects: Genetics and Genomics.