Virus & its Discovery
Viruses are abundant in nature and can infect and parasitized is a living organism from bacteria to mammals. They are considered to be very simple biological entities composed of a small number of macromolecules produced by and thus derived from the organism they infect. Viruses caused many diseases of international importance among the human viruses smallpox, polio, influenza, hepatitis, HIV, measles, and severe acute respiratory syndrome coronavirus are particularly well-known antibiotics can be very effective against diseases caused by bacteria this treatment are ineffective against viruses and most control measure relay on vaccine for relief of the symptom to encourage the body’s own one defense system. Viruses can also cause many important plant diseases and are responsible for huge losses and crop production and quality in all parts of the world.
Viruses lie on the borderline between the living and nonliving things. Viruses are considered as living because viruses possess DNA or RNA. They have the ability of reproduction they can undergo mutation and genetic recombination and also containing the ability to infect other living things and show irritability apart from this living characters viruses have also some non living characters they are subcellular or not cellular structure that do not respire excrete we can be crystallized and stored in much is the same way as chemicals.
The discovery of viruses take place by the late 1800 Louis pasture and Robert Koch and other pioneers bacteriologists had demonstrated that bacteria cause many diseases of man and other organisms. Some diseases confuse them m.ba cause he could not find bacteria for these diseases 16 disease was found to occur in the tobacco plants. It causes leaves to wrinkle and become mottled the mottled effect at the appearance of a mosaic and diseases was called the tobacco mosaic disease it was discovered that the virus would be held responsible for it which could be transmitted from an infected organism to healthy organism of the same kind. This was the first time demonstrated in 1892 by a Russian biologist name Iwanowski. He extracted the juice from the infected tobacco plant and state the used a very fine filter paper made up of porcelain the idea was to remove all the dictator from the juice living the bacteria-free filtrate next he rubbed some filtrate on the leaves of the healthy tobacco plant which soon short symptoms of the disease.
The true nature of viruses was the first time evident in 1935 when w Stanley prepare an extract from the tobacco mosaic virus and purified it after many successful attempts under the compound microscope isolated viruses appeared is a silvery crystal within a short time. It was found that the viruses’ crystal were nucleoproteins. Like the nuclear proteins found in the chromosomes of the plant and animal when the tobacco mosaic virus crystal isolated by w m Stanley were observed with an electron microscope found to be composed of rod-shaped structures in the isolated purified condition. Stanley took a very small amount of purified tobacco mosaic virus resort in the water and rubbed it on the leaves of the healthy tobacco plant the leaves showed mottled condition. It was founded the amount of viruses had increased greatly this result shows that the production of the tobacco mosaic virus occurred in the living cells of the host this proves that viruses are living.