MollicutesFor nearly 70 years after viruses were discovered, many plant diseases were described that showed symptoms of general yellowing or reddening of the plant or of shoots proliferating and forming structures that resembled witches’ brooms. These diseases were thought to be caused by viruses, but no viruses could be found in such plants. In 1967, Doi and colleagues in Japan observed mollicutes, i.e., wall-less mycoplasma-like bodies in the phloem of plants exhibiting yellows and witches’ broom symptoms. That same year the same group showed that the mycoplasma-like bodies and symptoms disappeared temporarily when the plants were treated with tetracy-cline antibiotics. Since then, mycoplasma-like organisms (MLOs) that infect plants have been reclassified as phy-toplasmas, and some of them that have helical bodies and can be found in other environments besides plants are known as spiroplasmas.

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