a) Natural fertilizer:
Micro organisms act upon degradable waste and making the soil fertile.
b) Nitrogen fixation
Rhizobium bacteria living in the root nodules of leguminous plants enrich the soil by fixing the atmospheric nitrogen as nitrates.
c) Bio control agents:
Bacillus thuringiensis control insects trichoderma protects, roots and control plant pathogens. Baculoviruses attack insects and other arthropods.
(OR)
Microorganisms make compost from degradable waste, fix the atmospheric nitrogen.

Pathogens enter into the body through cuts and wounds in the skin, mouth or nose.

Disease causing micro organisms are called pathogens.
Pathogenic organisms are of 5 types :
i) viruses
ii) fungi
iii) worms
iv) bacteria
v) protozoa

A chemical that kills or inhibits the growth of micro organism and is used to treat infections. The antibiotic penicillin was obtained from the fungi Penicillium chrysogenum. It is used to treat diseases such as tetanus and diphtheria.

i) Bacilli - Rod shaped bacteria.
Eg. Bacillus anthracis
ii) Spirilla - Spiral shaped bacteria.
Eg. Helicobacter pylori.
iii) Cocci - Spherical or ball shaped bacteria
Eg. Streptococus pneumoniae
iv) Vibrio - Comma shaped bacteria
Eg. Vibrio cholera

Probiotics are live food supplements used in yoghurt and other fermented milk products. Eg. Lactobacillus acidophilus and Bifidobacterium bifidum. These bacteria improve the microbial spectrum in the gut and thus contribute to the following effects.
1. Decrease the risk of colon cancer.
2. Decrease cholesterol absorption.
3. Prevent diarrhoeal diseases by increasing the immunity power.

1. Eat a diverse range of foods.
2. Eat lots of vegetables, legumes, beans and fruit,
3. Eat fermented foods.
4. Don't eat too many artificial sweeteners.
5. Eat prebiotic foods.
6. Breast feed for atleast six months.
7. Eat whole grains.
8. Eat a plant-based diet.
9. Eat foods rich in polyphenols.
10. Take a probiotic supplement.

Human Diseases	Causative microorganisms	Mode of transmission	Symptoms	Preventive measures/ Treatment
Tuberculosis	Mycobacterium tuberculosis (Bacteria)	Through air and sputum of infected person	Persistent cough, blood mucus, loss of weight, breathlessness	BCG Vaccine
Cholera	Vibrio cholera (Bacteria)	By flies and by contaminated food and water	Watery diarrhea, vomiting, rapid dehydration.	Anticholera vaccine, maintaining personal hygiene.
Common cold	Influenza (virus)	Through air	Running nose, sneezing	Isolation of patient
Rabies	Rhabdo viridae (virus)	Animal Bite	Fever, hallucination, paralysis inability to swallow	Anti-rabies vaccine.
Amoebic dysentery	Entamoeba histolytica (Protozoa)	Food water and flies	Severe diarrhea and blood in stool	Proper sanitation to be followed and metronidazole antibiotic to be, administered
Malaria	Plasmodium (Protozoa)	Female Anopheles mosquito	Nausea, vomiting High fever	Antimalarial drugs like quinine, chloroquine, to be taken and also usage of mosquito repellents and nets.

We obtain antibiotics and vaccines from microbes.
Antibiotics:
The word 'Anti' means against. Antibiotic is a substance produced by living organisms which is toxic for other organisms. Sir Alexander Fleming was the first person to discover the antibiotic penicillin in the year 1928. The antibiotic penicillin was obtained from the fungi penicillium chrysogenum. It is used to treat disease such as tetanus, diphtheria, antibiotic streptomycin is obtained from Streptomyces bacteria to cure various bacterial infections eg, Plague.
Vaccines:
Vaccines are prepared from dead or weakened microbes - Edward Jenner was the first person to discover small pox vaccine. He coined the term vaccination. When the vaccine is injected to the body of a patient, the body produces antibodies to fight against the germs. These antibodies remain inside the body and protects from future invasion of the germs. Therefore vaccination is otherwise called as immunization.
Eg: MMR vaccine for measles, Mumps, Rubella.
BCG (Bacille Calmette Guerin) vaccine for tuberculosis.

Bacteria are single-celled prokaryotes (cells without nuclei). They are considered to be the first living organisms on earth. Bacteria are grouped under the Kingdom Monera. The study of bacteria is called Bacteriology. The size of bacteria range from 1 μm to 5 μm (micrometer). Bacteria are of two types based on respiration


i) Aerobic bacteria (requires oxygen)
ii) Anaerobic bacteria (Does not requires oxygen)
Cell Structure:
A bacterium has on outer covering known as the cell wall. Nuclear material is represented by a nucleoid without nudear membrane. An extra chromosomal DNA called plasmid is present in the cytoplasm. Protein synthesis is carried out by 70 S ribosomes. Other cell organelles (mitochondria, golgi body, endoplasmic reticulum etc.) are absent flagella aid in locomotion.