Spiroplasma taxonomy and identification of the sex ratio organisms: can they be cultivated?

The spiroplasmas that occur naturally in several species of Drosophila were the first spiroplasmas ever observed, even though their discoverers, D.F. Poulson and B. Sakaguchi, in 1961 described them as being "treponema-like spirochetes." These Drosophila spiroplasmas are transovarially, or maternally, transmitted by infected females whose progenies are composed entirely of females. A more recently discovered Drosophila spiroplasma found in flies originating in Ito, Japan, is also maternally inherited but does not result in the elimination of males from the progeny of infected females. In spite of their early discovery, their high numerical density in the hemolymph of infected females (10(6)-10(7)/microliters), and numerous attempts at in vitro cultivation, they remain prime examples of non-cultivable spiroplasmas. It is the purpose of this paper to recount some of the approaches used in attempts at their cultivation.