In this article we will discuss about the history of virology and bacteriology.
History of Virology:
Viruses are very small and ultra-microscopic structures responsible for causing serious diseases both in plants and animals including man. The term virus is derived from a Latin word vios meaning venum or poisnous fluid. Viral diseases of plants were known long before the discovery of bacteria.
Charles Ecluse (1576) was first to describe plant virus disease as variegation in the colour of tulip flowers. Pasteur (1880) studied canine rabies and used the term virus (L. poison) for the first time.
Adolf Mayer (1886), a Dutch agricultural chemist, observed mottling disease in leaves of tobacco plants and named it mosaikkrankhet i.e., mosaic. He showed that tobacco mosaic was infectious but he failed to isolate any causal organism from the diseased tissue. D. Iwanowski, a Russian botanist, gave the first scientific demonstration of existence of a virus in 1892.
During his experiments on diseases of tobacco plant he extracted some of the sap from the diseased portion and filtered it through bacteria proof filters (bacteria cannot pass through such filters). He was surprised to note that the filtered sap had the power of producing the mosaic disease when rubbed on the healthy leaves of tobacco plants.
Loeffler and Frosch (1898) showed that “foot and mouth disease” among cattle was also due to some filterable agents.
Beijerinck (1898), a Dutch scientist, named this infectious fluid as “contagium vivum fluidum” (contagious living fluid). More and more diseases of both plants and animals were demonstrated to be caused by similar filterable agents. F. W. Twort (1915) observed death of bacterial colonies d’Herelle (1917) confirmed his work and coined the term ‘bacteriophage’ (the bacteria eater).
From 1935, started entirely a new phase in the virus research when W. M. Stanley, an American biochemist isolated the TMV in the form of fine needles or para-crystals. Bawden and Pirie (1937) studied the chemical nature of TMV and showed that the crystalline preparation of the virus consists of protein and nucleic acid.
Hershey and Chase (1952) demonstrated independent functions of viral protein and nucleic acid in the growth phase. Hall (1955), Brenner and Home (1959) studied the morphology and structure of virus, using electron microscope. According to A. Lwoff (1966), a Nobel laureate, French virologist, the most appropriate definition of viruses is “viruses are viruses”.
Luria and Darnell (1968) defined “viruses are entities whose genome is an element of nucleic acid either DNA or RNA which reproduce inside living cells and use their synthetic machinery to direct the synthesis of specialized particles, the virions which contain the viral genome and transfer it to other cells.”
Viruses are now defined as “ultramicroscopic disease producing entities living in a host as obligatory intracellular parasites.”
The branch of botany that deals with the study of virus is known as virology and the people dealing with this subject as virologists.
History of Bacteriology:
Bacteria (Gr. bakterion = small shaft, stick) are too small, microscopic, prokaryotic unicellular, organisms usually without chlorophyll. Antony Van Leeuwenhoek of Holland was the first to discover bacteria on June 10, 1675. Because of their motility, he thought them to be tiny animals and described them as little animalcules.
He observed them in a rain drop and drawn by the aid of his self-made lenses. A large number of microbial forms which included bacteria and protozoa were drawn. Linnaeus (1758) placed them in the genus vermes. The term bacteria to these animalcules was coined by Ehrenberg (1828). However, bacteria as group were recognised by Nageli (1857), who proposed the name Schizomycetes for this group.
The importance of these observations was, however, realized only after Pasteur (1876) when he demonstrated their role in fermentation and decay. He also confirmed bacteria as agents of various diseases, and started scientific study of these microbes.
He also discarded the theory of spontaneous generation (micro-organism arising from the pre-existing living entities). Later, Robert Koch (1876) proved that bacteria can cause diseases in human and animals e.g., cholera, leprosy, typhoid, tuberculosis etc. He discovered bacteria causing anthrax and tuberculosis. He restated certain principles relating to the germ theory of diseases. Now-a-days, these principles are known as Koch’s Postulates or Koch’s law.
He was awarded Nobel prize in 1905 for his work. Joseph Lister (1878) discovered the antiseptic theory (clearing and dressing the wounds by carbolic acid spray). Since then, particularly during the last 80 years, a vast knowledge about them has accumulated.
It is now well recognized that of all the organisms bacteria are more closely related with the life of man. The branch of botany dealing with the study of bacteria is known as bacteriology.