|Henegar, Roberta - Bobbie|
Submitted to: International Journal of Systematic and Evolutionary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/1998
Publication Date: N/A
Citation: N/A Interpretive Summary: Sex ratio disease, causes progenies from Drosophila fruit flies to be entirely female. The disease is caused by a spiroplasma, a helical bacterium that has no cell wall. The spiroplasmas proved to be extremely difficult to grow, but were, in 1986, cultivated in a very complex insect cell-free medium after initial co-culture with insect cells. The cultivated organisms induced the SR trait when injected into normal flies. Cultivation also permitted characterization. Strain DW-1 cells were helical, motile filaments 200-250 nm in diameter and were bound by a single 3-layer membrane. The temperature range for growth was 26 to 30C, with optimum growth at 30C, and a doubling time in H-2 medium of 15.8 h. Tests with antibodies showed the organisms to be related, but different from, other organisms. The genome size of strain DW-1 was 2040 kbp, with a DNA content of 26 + 1% guanosine plus cytodine. This spiroplasma, was designated Spiroplasma poulsonii. This information will be useful to those studying sex ratio traits for insect control, particularly those developing transgenic insects as a control methodology. Spiroplasmas, which in many cases invade the insect blood cavity, and in some cases transform cells, may find application, like Wolbachia bacteria, as pathogens that can spread insect lethal genes throughout an insect population. There has also been interest by researchers in pursuing the Drosophila fruit fly spiroplasma directly as a weapon for biological control of medfly (Mediterranean fruit fly).
Technical Abstract: The sex ratio trait causes progenies from wild-type Drosophila females to be entirely female. The trait is caused by a spiroplasma, designated group II. The organisms proved to be extremely fastidious, but were, in 1986, cultivated in a very complex cell-free medium (H-2) after initial co-culture with insect cells. The cultivated organisms induced the SR trait when injected into normal flies. Cultivation permitted characterization. Strain DW-1 cells were helical, motile filaments 200-250 nm in diameter and were bound by a single trilaminar membrane. The temperature range for growth was 26 to 30C, with optimum growth at 30C, and a doubling time in H-2 medium of 15.8 h. Variable, usually low-level reciprocal cross-reactions, were observed between antisera to strain DW-1 and representatives of group I subgroups. 16S rRNA sequence analyses of Weisburg et al. showed strain DW-1 to be most closely related to group I species. The genome size of strain DW-1 was 2040 kbp, as determined by pulsed-field electrophoresis. The G+C content was 26 plus or minus 1%, as determined by buoyant density and melting point methods. Serological and molecular data indicate that strain DW-1 is sufficiently separated from group I strains to justify retention of its group status. Continued group designation is also indicated by the ability of SR spiroplasmas to induce male lethality, their vertical transmissability, and their extremely fastidious growth requirements. We designate group II spiroplasmas, represented by strain DW-1, ATCC 43153, as Spiroplasma poulsonii.