It is 950 A° in length and 650 A° in width. This shape is also known as elongated icosahedron. The head is hexagonal and like a prism in outline (Fig 1A, B). These viruses are generally tadpole shaped i.e., a ‘head’ followed by a ‘tail’. With the help of electron microscope, the morphology of the bacteriophage has been studied. The DNA of these viruses also contains cytosine. These viruses have an angular head and non-contractile tail. These are temperate viruses as their genetic material becomes integrated with bacterial chromosomes and the host remains unaffected. These viruses have an angular head and a short non-contractile tail. These are also called virulent as they cause death of the host cells. These viruses are most thoroughly studied viruses. The DNA contain a unique base 5-hydroxyl methyl cytosine in place of cytosine. These phages have an angular head and contractile tail. They have been classified into many arbitrary groups such as: (i) T-Even Phages (T 2, T 4, T 6): The types of coli-phages have been called as T-phages. The bacteriophage capable of destroying E. coli has been studied most extensively from this point of view. Some viruses parasitize Actinomycetes (actinophages), yeast cells (zymophages) and blue green algae (cyanophages). They are abundant in soil, sewage, intestine of men, animals, insects, vegetables, milk etc. They may be found in nature where bacteria are growing. They are also known as phages.īacteriophage are obligate parasites and are dependent on living bacteria for their growth. d’Herelle (1917) termed the virus which destroys bacteria as bacteriophage, which literally means ‘bacteria eaters’ (Greek phage-to eat). This is known as Twort-d’Herelle phenomenon. The clear broth filter again added to a fresh culture of the susceptible bacteria, which cleared bacteria.
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