Question

Contrast the general penetration mechanisms utilized by animal viruses to that utilized by large bacterial viruses.

Answer 1

In case of animal virus , specific surface attachment proteins are present on the surface of the viruses which binds to the specific receptors on the surface of the animal cells. These receptors are mainly either glycoprotein or glycolipids. The specific binding of the surface attachment proteins and the receptors determines the host range.

The receptors are present on the coated pits. These coated ptis pinch of and then forms coated vesicles. The vesicles then get uncoated and get fused to endocytic vesicles which then ultimately fused to lysosomes. As the environment turns to acidic , virus undergo conformational changes which help in membrane fusion and release of the necleocapsid into the cytoplasm.

In case of bacterial virus host range is determined by the specificity of adsorption which depends upon the nature of receptor of bacteria. Protein and lipopolysaccharides serves as a receptor for bacterial cell. Once the bacteriophage is gets attached to the receptor virus starts releasing some protein complexes and capsid proteins which produceshole in the capsid envelope. Further phage membrane is subjected to structural regouping to form tubular tail which penetrates into the bacterial cell. The phage's tail consists of some lytic proteins which forms holes in the bacterial outer membranes. Once the tail reaches to the inner membrane, it fuses to it and the phage releases its genetic material into the hosts cytoplasm.