Electron microscopy of the segmented RNA genome ofLa Crosse virus: absence of circular molecules

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Abstract
The 3 species of single-stranded RNA present in La Crosse virus were examined by EM. Because large amounts of contaminating cellular [baby hamster kidney BHK-21 cells] DNA are copurified with the virus, despite extensive attempts to purify the virus, it was necessary to use procedures that eliminated the bulk of this DNA before the viral RNA was analyzed. When this was done, the modal lengths of La Crosse virus RNA were 0.4, 2.0 and 3.1 .mu.m. These lengths correspond well to their known MW of 0.4 .times. 106, 1.8 .times. 106 and 2.9 .times. 106, respectively. Under the denaturing conditions used to permit complete spreading of these single-stranded RNA molecules, no single-stranded circular molecules are observed. Therefore, the circular nucleocapsids present in La Crosse virus and some other bunyaviruses [Lumbo virus and Uukuniemi virus] do not appear to be due to covalent linkage of the ends of the RNA genome.