(i) Diphtheria
(ii) Whooping cough
(iii) Leprosy
(iv) Plague.

Streptococcus
Streptokinase functions as a clots from the blood vessels of patients who have suffered myocardial infarction.

Propionibacterium sharmanii
1.Since this bacterium produces large amount  of carbon dioxide during fermentatiom. large holes are produced.

Microbes are found everywhere, i.e. in soil, water, in/on plants, animals, human, etc. They play very important role in human life in many ways. for example,
(i) in human life products like baking bread, idli, cheese, beer, wine, vinegar, etc.
(ii) enzymes, amino acids, vitamins, antibiotics, organic acids and alcohols are commercially manufactured from the microorganisms.
(iii) live attenuated virus, bacteria and protozoans have been used to develop vaccines for protection from dysentery, typhoid, cholera, etc.
(iv) microbes play an important role in agriculture and recycling of important elements like oxygen, carbon, nitrogen, sulphur and phosphorus.
(v) microbes are used as biocontrol agents in place of pesticides, herbicides, etc.

Certain bacteria and cyanobacteria are nitrogen fixers.They convert atmospheric free nitrogen into ammonium form which is easily assimilated by higher plants.Thus, these microorganisms increase the fertility of soil without causing any environmental harzards and therefore, called biofertilizers.Example - Rhizobium and Anabaena.   

(i) Acetic acid - Acetobacter aceti
(ii) Butyric acid - Clostridium butylicum
(iii) Lacteric acid - Lactobacillus delbruekii

The treatment of sewage Involves two steps:
(i) Primary treatment and
(ii) Secondary treatment.
(i) Primary treatment
1. Primary treatment is a physical process of removal of small and large particles through filtration and sedimentation.
2. The first step is to remove the floating objects (like polythene bags) by letting the sewage to pass through wire mesh screens of sequentially smaller pore sizes.
3. Then the sewage is passed into the grit chamber, where grit is sedimented.
4. The sewage is allowed to go into the primary settling tank, where the suspended materials settle down to form primary sludge.
The effluent is taken for secondary treatment.
(ii) Secondary Treatment
1. It is a biological process, that employs the heterotrophic bacteria naturally present in the sewage.
2. The effluent from the primary treatment is passed into large aeration tanks, where it is constantly agitated and air is pumped into it.
3. This allows the rapid growth of aerobic bacteria into flocs, which consume the organic matter of the sewage and reduce the BOD.
4. The effluent is passed into a settling tank, where the flocs are allowed to sediment forming the activated sludge.
5. A small part of the activated sludge is pumped back into aeration tank as inoculum.
6. The remaining major part of the sludge is pumped into anaerobic sludge digesters, where the anaerobic bacteria digest the organic matter and produce methane, hydrogen sulphide and carbon dioxide.
7. The effluent from this is passed into the waterbody.

(a) Leguminous plants harbour Rhizobium in their root nodules; the bacterium fixes atmospheric nitrogen and enriches soil fertility.
(b) Cyanobacteria enrich soil fertility by
(i) fixing atmospheric nitrogen in the soil as nitrogen compounds.
(ii) adding organic matter through their photosynthetic activity.
(c). Mycorrhizae absorb phosphorus from the soil and pass it on to the plant; they provide resistance to root-borne pathogens and tolerance to salinity and drought.

MOEF of Government of India has initiated the Yamuna Action Plan and Ganga Action plan for saving Yamuna and Ganga rivers respectively.
Ganga Action Plan:
1.Due to increased urbanisation and industrialisation there is a huge quantity of sewage produced; but there are not enough sewage treatments plants and hence the untreated sewage is let into major rivers.
2. The government has planned to build a number of sewage treatment plants, because the sewage and effluents from the areas nearby Ganga rivers can be treated before they are let into the river.
3. The objective of Ganga Action Plan is to save the river from pollution.
Yamuna Action plan :
In order to protect the major rivers of India from sewage pollution, the Ministry of Environment and Forests has initiated development of sewage treatment plants under the National River Conservation Authority, e.g., Ganga Action Plan and Yamuna Action Plan. Industries contribute chemical effluents to the river's pollution load and the toxicity kills aquatic animals in large sections of the river.

Biofertilisers are those organisms which enrich the soil fertility.
Categories of organisms:
(i) Bacteria, e.g. Rhizobium, Azotobacter
(ii) Cyanobacteria, e.g. Nostoc, Aulosira
(iii) Mycorrhizae/fungi, e.g. Glomus
Functions:
1. Bacteria and Cyanobacteria fix atmospheric nitrogen and increase the nitrogen content of the soil.
2. Cyanobacteria also add organic matter to the soil through their photosynthesis.
3. The fungi decompose the organic matter of the soil and make the nutrients available to the roots.
4. Mycorrhizae help in absorption and storage of some mineral nutrients like phosphorus for the plants.