Definitions [4]
Define the following term
Zymology
Zymology is an applied science which deals with the biochemical process of fermentation and its practical uses.
Define the following term
Antibiotics
Antibiotics are chemical substances produced by microorganisms which can kill or retard the growth of other disease causing microbes even in low concentration. Antibiotic means “against life”.
Define the following terms
Superbug
"Superbug" is a term used to describe strains of bacteria that are resistant to the majority of antibiotics commonly used today.
Define bioherbicides.
Bioherbicides are living creatures such as microbes, fungi, insects, or other pathogens that are employed to restrict the population of undesired plants in agricultural fields, ponds, lakes, and so on.
Key Points
Key Points: Microbes in Household Products
| Product | Micro-organisms Used | Function |
|---|---|---|
| Curd | Lactobacillus (LAB) | Converts milk into curd, increases vitamin B₁₂ |
| Butter | Streptococcus cremoris, Leuconostoc dextranicum | Gives flavour and aroma |
| Yogurt | Lactobacillus bulgaricus, Streptococcus thermophilus | Ferments milk at 40°C |
| Cheese | Streptococcus lactis, Leuconostoc, fungi | Curdling and ripening of cheese |
| Swiss Cheese | Propionibacterium shermanii | Produces CO₂, forms holes |
| Roquefort Cheese | Penicillium roqueforti | Ripening and flavour |
| Camembert Cheese | Penicillium camemberti | Soft texture and taste |
Key Points: Microbes in Industries
- Bio-active Compounds — Streptokinase (Streptococcus) = clot buster; Statins (Monascus purpureus) = lowers blood cholesterol.
- Antibiotics — Penicillin (Penicillium chrysogenum), Streptomycin (S. griseus), Erythromycin (S. erythreus), Oxytetracycline (S. aurifaciens), Bacitracin (Bacillus licheniformis).
- Alcoholic Beverages — Yeast (Saccharomyces cerevisiae) ferments cereals/fruit juices. Distilled = Whisky, Brandy, Rum; Non-distilled = Wine, Beer. Fenny = Goa's cashew wine.
- Organic Acids — Citric & Gluconic acid (Aspergillus niger), Acetic acid/vinegar (Acetobacter aceti), Fumaric acid (Rhizopus arrhizus).
- Vitamins — B₂ (Neurospora gossypii), B₁₂ (Pseudomonas denitrificans), Vitamin C (Aspergillus niger).
- Industrial Enzymes — Invertase (S. cerevisiae), Lipase (Candida lipolytica), Cellulase (Trichoderma konigii), Pectinase (Aspergillus niger).
- Gibberellins — Isolated from fungus Gibberella fujikuroi; ~15 types; used for parthenocarpy, seed dormancy breaking, flowering induction & enlarging grape fruits.
Key Points: Microbes in Sewage Treatment
- Sewage = 99.5–99.9% water + 0.1–0.5% organic/inorganic matter + microbes (bacteria, viruses, fungi, algae, etc.)
- Preliminary Treatment — Bar screens remove large solids; Grit Chamber removes sand & stones.
- Primary Treatment — Sedimentation tank settles suspended solids; reduces coliform bacteria. Removes ~50–70% solids.
- Secondary Treatment — Aerobic bacteria decompose organic matter in aeration tanks; lowers BOD by 70–80%.
- Tertiary Treatment — Anaerobic bacteria digest sludge in sludge digesters; disinfection improves water quality.
- Chlorination — Kills remaining pathogenic bacteria before water release.
- Disposal — Treated water → natural water bodies; digested sludge → proper disposal/manure.
Key Points: Microbes as Biocontrol Agents
- Meaning — Biocontrol agents are microbes that control pests by causing disease, competing with, or killing them, reducing dependence on chemical pesticides.
- Biopesticides — Safer, eco-friendly alternative to chemical pesticides. Key agents: Bacillus thuringiensis (Bt) → caterpillars, beetles; Beauveria bassiana → aphids, mites, white flies; Nosema locustae (protozoa) → grasshoppers, crickets; NPV & Granulovirus → gypsy moths, ants, wasps.
- Bacillus thuringiensis (Bt) — Dried spores mixed with water and sprayed on plants to kill butterfly caterpillars. Most widely used bacterial biocontrol agent.
- Trichoderma — A fungus that acts as a biocontrol agent specifically against soil-borne fungal plant pathogens.
- Microbial Herbicides — Phytophthora palmivora → milkweed; Alternaria crassa → water hyacinth; Fusarium spp. → most weeds; Pseudomonas, Xanthomonas, Agrobacterium → several weeds.
- Insects as Herbicides — Tyria moth controls Senecio jacobeae weed; Cactoblastis cactorum controls cacti weeds.
Key Points: Types of Biocontrol Agents
| Category | Biocontrol Agent | Target / Use |
|---|---|---|
| Insects | Ladybird beetle | Controls aphids |
| Insects | Dragonfly | Controls mosquitoes |
| Viruses | Baculoviruses (NPV) | Control insect pests like bollworm |
| Bacteria | Bacillus thuringiensis | Controls insect pests and mosquito larvae |
| Bacteria | Agrobacterium radiobacter (K-84) | Controls crown gall disease |
| Bacteria | Pseudomonas sp. | Controls fungal disease (damping off) |
| Fungi | Trichoderma sp. | Controls many plant diseases |
| Fungi | Beauveria, Metarhizium, Verticillium | Control insect pests |
| Fungi | Aschersonia aleyrodis | Controls whiteflies |
Key Points: Microbes as Biofertilizers
- Biofertilizers are living micro-organisms that improve soil fertility by increasing the availability of nutrients to plants.
- They are eco-friendly alternatives to chemical fertilizers, which degrade soil quality and reduce microbial life.
- Nitrogen-fixing microbes such as Rhizobium, Azotobacter, Azospirillum, and Frankia convert atmospheric nitrogen into usable forms.
- Legume–Rhizobium symbiosis forms root nodules that fix large amounts of nitrogen and enrich the soil for subsequent crops.
- Azolla–Anabaena symbiosis and cyanobacteria are widely used in paddy fields and significantly increase rice yield.
- Mycorrhiza (fungus–root association) enhances absorption of phosphorus and other minerals and protects plants from pathogens.
- Phosphate-solubilizing bacteria and fungi convert insoluble phosphates into forms available to plants.
- Biofertilizers improve crop yield, reduce fertilizer requirement, and help in sustainable agriculture and soil conservation.
