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A virus has either a DNA or an RNA genome and is called a DNA virus or an RNA virus, respectively. The vast majority of viruses have RNA genomes. Plant viruses tend to have single-stranded RNA genomes and bacteriophages tend to have double-stranded DNA genomes.
Viruses in Bacteria, Plant and Fungi. Viruses are too small to be seen by the naked eye. They can't multiply on their own, so they have to invade a 'host' cell and take over its machinery in order to be able to make more virus particles.iruses and other genetic elements are common inhabitants of fungi. As viruses have a small genome, increased virulence resulting from a chance mutation is likely. Some of the principles of this page apply to all microbes associated with the host, and some are specific to viruses.