Ultrastructure of Bacterial Viruses PDF

Mter the discoveryof the tobacco mosaic virus by D. I. Ivanov­ skU in 1892 [14], the new science of virology was born and began to develop rapidly. The number of viruses now known is enormous and they can infect nearly all animal and plant organisms. Microorganisms themselves are no exception to this rule. Despite intensive study of Vlruses, their origin and nature are still a subject for speculation and hypothesis. The general concept of viruses embraces a wide group of biologically active structures occupying an intermediate position between living and nonliving matter. The dual character of viruses is determined by the fact that, while they do not possess an inde­ pendent system of metabolism, which is a characteristic feature of every living being, they nevertheless carry within themselves all the necessary information for autoreproduction. A striking feature of the virus is that it consists essentially of two components: a protein envelope and the nucleic acid con­ tained within it. In contrast to the elementary structural unit of the living or­ ganism, the cell, which contains two types of nucleic acid (DNA and RNA), the virus particle contains only one type of nucleic acid - either DNA or RNA. It is perhaps this which is responsible for the imperfection of the virus as a living organism.

The type of genetic material found in a particular virus depends on the nature and function of the specific virus. The genetic material is not typically exposed but covered by a protein coat known as a capsid. The viral genome can consist of a very small number of genes or up to hundreds of genes depending on the type of virus. Note that the genome is typically organized as a long molecule that is usually straight or … Ultrastructure of bacteriophage and bacteriocins.