Nano-fibers produced by viral infection of amoeba visualized by atomic force microscopy

In the course of an atomic force microscopy investigation of mimivirus, we observed that disrupted virions released masses of fibers that were several hundreds of nanometers in length and that could not be explained as nucleic acid or polysaccharide. The fibers exhibited a strong 7 nm periodicity along their lengths. They existed singly, and also as ribbons, cables, and in multi stranded coils. In the aggregate structures, the periodic bands of the individual fibers aligned laterally to produce ribbons and other superstructures having a corresponding pattern of 7 nm periodic transverse bands. We have not observed such fibers in studies of other virus and cellular systems. The fibers are mechanically flexible and resistant to breakage. Occasionally fibers were associated with toroidal protein complexes, assumed to be processive enzyme complexes, apparently in the act of modifying the fibers.