Introductory Microbiology

Germ Theory of Disease

Importance of Soil fertility

• Paraghaph 1:Soil fertility refers to the capacity of soil to supply plant nutrients. Soil fertility and fertilizers are very much closely related terms; one cannot neglect one from the other in their function. Soil fertility acts as a ‘SINK’ where in plants can draw nutrients for maximum yield, where as fertilizer, acts as a ‘SOURCE’ wherein we can draw continuously different nutrients. The importance of soil fertility and fertilizer management is being increasingly recognized in all countries recently to meet the demand for food and other agricultural raw materials.
  

• Recognition of agents of infection first to be recognized were fungi: Agostinod Bassi (1836) demonstrated that a fungus was the cause of disease (of silk worm), the etiologic role of bacteria was established by Koch (1876) for anthrax. The pure culture preparation is the key to the identification. Koch perfected the technique of identification including the use of solid media and the use of stain. After identifying the tubercle bacillus Koch formalized the criteria, introduced by Henle in 1840 but known as Koch’s postulates, for distinguishing a pathogenic form an adventitious microbe:
1. The organism is regularly found in the lesion of the disease.
2. It can be isolated in pure culture.
3. Inoculation of this culture produces a similar disease in experiments on animals.

These criteria have proceeded invaluable in identifying pathogens, but they cannot be met: some organism such as viruses cannot grow on artificial media and some are pathogenic only for man. Golden era of microbiology was established between 1860 and 1910 because of development of powerful methodology. Moreover, various members of the German school isolated (in addition to the tubercle bacillus), the cholera vibrio, Typhoid Bacillus, Diphtheria, Bacillus, Pneumococcus, Staphylococcus, Streptococcus, Meningococcus, Gonococcus and Tetanus bacillus.