Viroids
Viroids are infectious pathogens that affect only plants, there for are also called as plant pathogens.
Characteristics Features of Virus
- Viroids contain only RNA.
- These are known to be smaller in size and infect only the plants.
- Viriods are the species of nucleic acid with relatively low molecular weight and unique structure.
- They reproduce within the host cell which they affect in and cause variation in them causing deaths.
- Viriods are said to move in an intra cellular manner, cell to cell through the plasmodesmata and a long distance through the phloem.
The term prion is derived from proteinacious infectious particle.
Characteristics Features of Prions
- Prions are smaller than viruses and can only seen through electron microscope when they form cluster.
- They do not contain nucleic acid
- Prions are resistant to procedures that destroy pathogens by breaking down nucleic acid.
- Cellular enzymes referred to as proteases can breakdown the normal protein; however, prion proteins are unfortunately resistant to this and subsequently accumulate in the brain tisuues as they replicate.
- Viruses are used in preparation of sera and vaccines to be used against diseases like Rabies, Polio
- Multiplication of viruses in bacterial cell is also utilized in the production of antibiotics.
- Due to simplicity of structure and rapid multiplication, they are widely used in research in the field of molecular biology, medicine and genetic engineering.
- Viruses cause deadful diseases in crop plants, domesticated animals and man.
- Bacteriophages attack the nitrogen fixing bacteria of soil and the responsible for reducing fertility of the soil.