Electron Microscopy of the RNA of Foot-and-Mouth Disease Virus

Bundesforschungsanstalt für Viruskrankheiten der, Tiere, 74 Tübingen Postfach 1149 Germany Electron microscopic examination of molecules of single-stranded RNA requires their visualization as isolated and elongated strands. Inter- or intramolecular hydrogen bonding, which presumably is responsible for aggregation and tangling of single-stranded RNA, can be broken by the use of urea (Granboulan, Huppert & Lacour, 1966). Furthermore, incubation of purified reovirus with urea before spreading has been demonstrated as a gentle procedure for the release of double-stranded RNA (Granboulan & Niveleau, 1967; Vasquez & Kleinschmidt, 1968). We describe here morphological studies on the RNA of foot-and-mouth disease virus. The method employed was the microdiffusion technique recently developed by Mayor & Jordan (1968) from the protein monolayer method of Kleinschmidt & Zahn (1959). A droplet of the virus suspension was mixed with a droplet of a 4 to 10 M -urea solution on an iced sheet of Teflon or dental wax. * Presented in part at the International Pilot Conference on Foot-and-Mouth Disease, Gustav Stern Foundation, New York, 25 and 26 May 1969, and at the ‘32. Tagung der Deutschen Gesellschaft für Hygiene und Mikrobiologie’, Münster, 28. Mai 1969. Received 12 August 1969; accepted 13 November 1969.