ICSE 9 Biology Economic Importance Short

⚡ Quick Revision : Bacteria in Medicine

1. Antibiotics: The Chemical Weapons

Antibiotics are chemical substances produced by a microorganism which can kill or inhibit the growth of other disease-causing microorganisms.

• ✔ First Antibiotic: Penicillin, discovered by Alexander Fleming (1928) from the fungus Penicillium notatum.
• ✔ Bacterial Sources: Streptomyces is a genus of bacteria used to produce Streptomycin, Chloromycetin, and Tetracycline.

2. Criteria for a Good Antibiotic

Criterion	Importance
Broad Spectrum	Should be effective against a wide range of different bacteria.
Selective Toxicity	Must kill pathogens without harming the host's (human) tissues.
No Side Effects	Should not produce allergic reactions or damage normal flora.

3. Vaccines (Immunization)

A vaccine is a preparation of killed or weakened (attenuated) germs that is introduced into the body to stimulate the production of antibodies.

• Killed Germs: TAB vaccine for typhoid.
• Attenuated Germs: BCG vaccine for tuberculosis.
• Toxoids: Altered toxins of bacteria used for Diphtheria and Tetanus.

Biological Reasoning

Question: Why is Serum used to provide immediate immunity?
Answer: Serum contains "readymade" antibodies (antitoxins). Unlike vaccines, which take time to work, serum provides passive immunity instantly for emergencies like snake bites or tetanus.

❌ Don't Confuse:

Antibiotics are used to treat an existing infection. Vaccines are used to prevent a future infection by building immunity.

⚡ Quick Revision : Bacteria in Agriculture

1. Nitrogen Fixation

Plants cannot absorb nitrogen gas directly from the atmosphere. Certain bacteria convert this free nitrogen into soluble Nitrates that plants can easily use.

• ✔ Symbiotic Bacteria: Rhizobium lives in the root nodules of leguminous plants (pea, gram, bean).
• ✔ Free-living Bacteria: Azotobacter and Clostridium fix nitrogen independently in the soil.

2. Nitrification & Decaying

Bacteria maintain soil fertility by recycling nutrients from dead organic matter through two main stages:

• A. Ammonification: Putrefying bacteria break down proteins from dead bodies into Ammonia.
• B. Nitrification:
  • Nitrosomonas converts Ammonia into Nitrites.
  • Nitrobacter converts Nitrites into Nitrates.

3. Denitrification (The Soil Loss)

While some bacteria add fertility, Denitrifying Bacteria (e.g., Pseudomonas) reduce soil fertility by converting nitrates back into free nitrogen gas.

Process	Bacteria Type	Effect on Soil
Nitrogen Fixation	Rhizobium	Increases Nitrogen
Nitrification	Nitrobacter	Forms usable Nitrates
Denitrification	Pseudomonas	Decreases Nitrogen

Exam Reasoning

Question: Why are bacteria called "Nature's Scavengers"?
Answer: Because they decompose dead plants and animals, cleaning the environment and returning nutrients to the soil to be reused by producers.

❌ Don't Confuse:

Nitrosomonas and Nitrobacter are nitrifying bacteria (Friends). Pseudomonas is a denitrifying bacterium (Foe to the farmer).

⚡ Quick Revision : Bacteria in Industry

1. The Dairy Industry

Bacteria are the primary agents in converting milk into various dairy products. The most important bacterium here is Lactobacillus.

• ✔ Curd Making: Lactobacillus ferments the lactose (milk sugar) into lactic acid, which coagulates the milk protein (casein).
• ✔ Cheese Production: Bacteria are added to curd to provide specific flavors and textures during the "ripening" process.

2. Fiber Retting & Tanning

Bacteria help in extracting natural fibers and preparing leather through specialized processes:

• A. Retting: Bacteria (e.g., Clostridium butyricum) dissolve the "pectin" (plant glue) that holds jute or flax fibers together. This allows the fibers to be easily separated.
• B. Tanning: Bacteria are used to break down the fats and soft tissues on animal hides to make them soft and durable for leather production.

3. Other Industrial Roles

Industry	Bacterial Action	Product/Result
Vinegar (Acetum)	Acetobacter oxidizes alcohol.	Acetic Acid (Vinegar)
Tea/Tobacco	Fermentation of leaves.	Improved Aroma & Flavor (Curing)
Vitamin Synthesis	Bacteria in human intestine.	Vitamin B & K

Exam Reasoning

Question: Why does milk turn sour faster in summer than in winter?
Answer: Bacteria like Lactobacillus thrive in warm temperatures (optimal around 30°C–40°C). In summer, the higher temperature speeds up their growth and the fermentation of lactose into lactic acid.

❌ Don't Confuse:

Curing in tobacco is for flavor, while Retting in jute is for fiber separation. Both use bacteria, but the industrial purpose is completely different.

⚡ Quick Revision : Economic Importance of Fungi

1. Yeast: The Baker's & Brewer's Friend

Yeast (Saccharomyces cerevisiae) is a unicellular fungus that performs Fermentation—the anaerobic breakdown of sugar into alcohol and carbon dioxide.

• ✔ Baking: The $CO_2$ released during fermentation causes the dough to rise (leavening), making bread light and fluffy.
• ✔ Brewing: In breweries, yeast ferments fruit juices or malted grains to produce Ethanol (Alcohol).

2. Fungi as Food & Vitamins

• A. Edible Mushrooms: Species like Agaricus bisporus (Button mushroom) are rich in proteins and vitamins.
• B. Single Cell Protein (SCP): Certain fungi are grown on a large scale as a protein-rich food supplement.
• C. Vitamin Synthesis: Yeast is a rich source of Vitamin B-complex.

3. Harmful Effects of Microorganisms

Activity	Organism Involved	Damage Caused
Food Spoilage	Bacteria & Molds	Putrefaction and souring of food.
Food Poisoning	Clostridium botulinum	Botulism (can be fatal).
Animal Diseases	Anthrax bacteria	Affects cattle and humans.
Plant Diseases	Puccinia (Fungi)	Black rust of wheat.

Exam Reasoning

Question: Why does bread become "holey" and soft?
Answer: During fermentation, yeast produces $CO_2$ gas. When the bread is baked, the gas expands and escapes, leaving behind tiny pores/holes that make the bread soft.

❌ Don't Confuse:

While Mushrooms are fungi and healthy to eat, many wild mushrooms (like Amanita) are poisonous (Toadstools). Never eat a mushroom found in the wild!

⚡ Quick Revision : Food Preservation

1. Why Preserve Food?

Food preservation is the process of treating and handling food to stop or slow down spoilage caused by microorganisms. The main goal is to eliminate moisture, heat, or oxygen—the three things bacteria need to thrive.

2. Common Preservation Methods

Method	Scientific Principle	Examples
Salting/Sugaring	Causes Plasmolysis (draws water out of bacterial cells).	Pickles, Jams, Salted Fish.
Boiling/Heating	Kills bacteria by denaturing their enzymes and proteins.	Boiling milk, Cooking food.
Refrigeration	Low temperature inhibits bacterial growth and enzyme activity.	Storing vegetables and meat.
Dehydration	Removes moisture, preventing microbial growth.	Dried fruits, Milk powder.

3. Pasteurization

A specialized method used primarily for milk, named after Louis Pasteur. It does not kill all microbes but eliminates disease-causing (pathogenic) ones.

• ! Step 1: Heating milk to about 63°C for 30 minutes (or 72°C for 15 seconds).
• ! Step 2: Cooling it instantly to prevent any surviving spores from germinating.

Critical Reasoning

Question: Why is salt added to meat or fish for storage?
Answer: High salt concentration creates a hypertonic environment. Through osmosis, water is pulled out of any bacterial cells present, causing them to shrink (plasmolysis) and die.

❌ Don't Confuse:

Sterilization kills ALL microorganisms (including spores). Pasteurization only kills harmful pathogens and preserves the taste and nutrition of milk better than boiling does.