What is the difference between antibiotics and antiseptics?

Antibiotics are chemicals produced by microorganisms that kill/inhibit bacteria at low concentrations — taken internally (e.g., penicillin, streptomycin). Antiseptics are chemical substances applied externally to living tissues to kill/inhibit microorganisms (e.g., Dettol, iodine). Disinfectants are used on non-living surfaces (e.g., phenol, bleach).

Why is Bacillus thuringiensis an ideal biocontrol agent?

Bacillus thuringiensis (Bt) produces crystal proteins (Bt toxins/Cry proteins) that specifically kill insect larvae (caterpillars) that eat Bt-treated crops. Advantages: (1) Specific — kills only target insects, not beneficial ones; (2) Biodegradable — breaks down naturally; (3) No chemical residue in food; (4) Bt genes can be inserted into crop plants (Bt cotton) for permanent protection.

What is the role of Rhizobium in nitrogen fixation?

Rhizobium lives in symbiotic association with legume roots (pea, soybean, pulses). It colonises root cells, forming nodules. Inside nodules, it converts atmospheric N₂ → NH₃ (ammonia) — a process called biological nitrogen fixation — using the enzyme nitrogenase. The plant supplies carbohydrates; Rhizobium provides fixed nitrogen. Legumes can grow in nitrogen-poor soils and enrich soil for future crops.

Microbes, Antibiotics and Biotechnology Applications

Microbes in Human Welfare • Class 12 Biology • NCERT • CBSE

Microbes are used to make yoghurt (Lactobacillus), cheese (Lactococcus), bread (Saccharomyces cerevisiae — yeast), antibiotics (Penicillium → penicillin; Streptomyces → streptomycin), biogas (methanogens), and organic acids (Acetobacter → acetic acid). Biocontrol agents: Bacillus thuringiensis (Bt) against insects.

Frequently Asked Questions

What is the difference between antibiotics and antiseptics?: Antibiotics are chemicals produced by microorganisms that kill/inhibit bacteria at low concentrations — taken internally (e.g., penicillin, streptomycin). Antiseptics are chemical substances applied externally to living tissues to kill/inhibit microorganisms (e.g., Dettol, iodine). Disinfectants are used on non-living surfaces (e.g., phenol, bleach).
Why is Bacillus thuringiensis an ideal biocontrol agent?: Bacillus thuringiensis (Bt) produces crystal proteins (Bt toxins/Cry proteins) that specifically kill insect larvae (caterpillars) that eat Bt-treated crops. Advantages: (1) Specific — kills only target insects, not beneficial ones; (2) Biodegradable — breaks down naturally; (3) No chemical residue in food; (4) Bt genes can be inserted into crop plants (Bt cotton) for permanent protection.
What is the role of Rhizobium in nitrogen fixation?: Rhizobium lives in symbiotic association with legume roots (pea, soybean, pulses). It colonises root cells, forming nodules. Inside nodules, it converts atmospheric N₂ → NH₃ (ammonia) — a process called biological nitrogen fixation — using the enzyme nitrogenase. The plant supplies carbohydrates; Rhizobium provides fixed nitrogen. Legumes can grow in nitrogen-poor soils and enrich soil for future crops.

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