AN INTRODUCTION TO VIRUS

 VIRUS

·       Acellular in nature.

·       Measured in nanometer (nm) and Size was ranged from Size – 20 nm to 1500 nm.

·       Viruses can be visualized only under Electron Microscope.

·       Also called as “Living Chemicals”

·       Replicates only inside the living cell.

·       Viruses can be cultivated only in living cells (Obligatory parasites).

·       Locomotion – Non – motile

·       Viruses cause large number of diseases in humans (such as AIDS, Common cold, Poliomyelitis, SARS, Herpes, Hepatitis etc), plants (Tobacco mosaic disease, Papaya ring spot disease, etc) and Foot and mouth disease of animals.

·       The largest virus is Gaint Virus (Pithovirus sibericum)

ü  Measures 1.5 µm (1,500 nm) in length. 

ü  Pithovirus sibericum was discovered in 2014 in a sample of 30,000 year old Permafrost (ground that completely frozen) in Siberia.

ü  Able to infect amoebas in laboratory settings despite its age.

ü Unlike typical viruses, these Giant viruses are large enough to be seen using Light microscopy.

·       Study of Virus – Virology.

·       Father of Virology – Martinus Williem Beijerinck

ü  Along with Dimitri Iwasaki, first demonstrations of a filterable Plant virus: Tobacco Mosaic Virus.

ü  At the end of the 19^th century, the Tobacco mosaic disease destroyed his Tobacco plants. At the time, it was thought that the plants were affected by bacteria or toxins. Beijerinck's research quickly ruled out the poison option. Healthy plants could get sick from the sap of diseased plants, even if this sap was filtered against bacteria. This meant there was a smaller pathogen than a bacterium that could pass through the filter. Beijerinck initially called this a "contagium vivum fluidum" which means "living infectious fluid". Beijerinck later used the word "virus", which at that time had the broad meaning "sickening things". Beijerinck first used this name for the small pathogen that we still know today.

ü  He stated that virus propagation was only possible in other living cells.

ü  He discovered that the Mosaic disease could not reproduce outside the plant, and the virus in the plant only multiplied in the growing parts.