Pathogenicity
changes and diseases. Therefore, the ability to cause pathogenicity of certain microorganisms is definitely
an unique noticeable characteristic feature that has virtually given a tremendous boost to the
earlier researches carried out with the microbes. It has been observed that comparatively a few microbial
variants actually produce disease, some microorganisms prove to be pathogenic for plants and animals,
and lastly certain microbes may bring about specific disease in other microbes.
Examples:
(
a) Bdellovibrio: A parasite that invades bacteria by forming a hole in the cell wall. It usually
lives and reproduces inside the cell.
(
b) Bacteriophage: A virus that infects bacteria. Bacteriophages are widely distributed in nature,
having been isolated from faeces, sewage, and polluted surface waters. They are regarded
as bacterial viruses, the phage particle consisting of a head composed of either RNA
or DNA and a tail by which it attaches the host cells.