Typhoid causative agent: Salmonella typhi
Mode of entry of the pathogen:
Through food and water contaminated with faeces of infected person and through houseflies.
Diagnostic symptoms:
High fever, weakness, abdominal pain, headache, loss of appetite, rashes on chest and upper abdomen.
Organ affected in severe cases:
Human Digestive system gets affected and the blood can carry the bacteria to other organs including the lungs, liver, gall bladder and kidneys.

The immunization schedule indicates the age at which the vaccine should be administered to protect the children from infectious diseases.

Viruses are categorized as
i) Plant virus:
Virus that infect plants,
eg: Tobacco mosaic virus, cauliflower mosaic virus, Potato virus.

ii) Animal virus:
Virus that infect animals
eg: Adenovirus, Retrovirus(HIV), Influenza virus

iii) Bacteriophages:
Virus that infect bacterial cells.
eg: T4 Bacteriophage

Microbes in Agriculture:
Microbes play an important role in agriculture as biocontrol agents and biofertilizers. Microbes play a vital role in the cycling of elements like carbon, nitrogen, oxygen, sulphur and phosphorus.
(i) Microbes as biocontrol agents:
1. Microorganisms used for controlling harmful or pathogenic organisms and pests of plants are called as biocontrol agents (Biopesticides).
2. Bacillus thuringiensis (Bt) is a species of bacteria that produces a protein called as 'cry' protein.
3. This protein is toxic to the insect larva and kills them.
4. Spores of B thuringiensis are available in sachets, which are dissolved in water and sprayed on plants infected with insect larva.
(ii) Microbes as biofertilizers
1. Microorganisms which enrich the soil with nutrients are called as biofertilizers.
2. Bacteria, cyanobacteria and fungi are the main sources of biofertilizers.
3. Nitrogen is one of the main source of plant nutrients.
4. Atmospheric nitrogen has to be converted to available form of nitrogen.
5. This is done by microbes either in free living conditions or by having symbiotic relationship with the plants.
6. e.g. Nitrosomonas Nostoc (free living), symbiotic microbes like Rhizobium, Frankia.
Microbes in Industries:
Microorganisms play an important role in the production of wide variety of valuable products for the welfare of human beings.
i) Production of fermented beverages:
Beverages like wine are produced by fermentation of grape fruits by Saccharomyces cerevisiae.
ii) Curing of coffee beans, tea leaves and tobacco leaves:
1. Beans of coffee and cocoa, leaves of tea and tobacco are fermented by the bacteria Bacillus megaterium.
2. This gives the special aroma.
iii) Production of curd:
Lactobacillus sp. converts milk to curd.
iv) Production of organic acids, enzymes and vitamins:
1. Oxalic acid, acetic acid and citric acid are produced by fungus Aspergillus niger.
2. Enzymes like lipases, invertase, proteases, and glucose oxidase are derived from microbes. Yeasts are rich source of vitamin-B complex.

Based on the shapes, bacteria are grouped as

1. Spherical shaped bacteria called as cocci or coccus for a single cell.
2. Rod shaped bacteria called as bacilli or bacillus for a single cell.
3. Spiral shaped bacteria called as spirilla or spirillum for single cell.