Control of Microorganisms for B.Sc. Botany & Biotechnology SEM-3 students
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Control of Microorganisms for B.Sc. Botany & Biotechnology SEM-3 students
Control of Microorganisms for B.Sc. Botany & Biotechnology SEM-3 students
- 1. Page | 1 Introduction Microorganisms, including bacteria, fungi, viruses, and protozoa, are omnipresent in the environment. While some are beneficial, others can be pathogenic and cause diseases. Controlling microbial growth is essential in medical, industrial, and laboratory settings to prevent infections, contamination, and spoilage. The control of microorganisms can be achieved through physical, chemical, and biological methods. 1. Principles of Microbial Control Microbial control involves inhibiting or eliminating microorganisms using different agents or techniques. The effectiveness of control methods depends on: • Microbial load (number of microorganisms present) • Type of microorganism (e.g., bacteria, viruses, fungi, spores) • Environment (e.g., temperature, pH, organic matter) • Duration of exposure to the control method • Concentration and potency of the control agent The primary goals of microbial control are: 1. Sterilization – Complete destruction/removal of all microbial life, including spores. 2. Disinfection – Elimination of most pathogens but not necessarily all spores. 3. Antisepsis – Inhibition or destruction of microorganisms on living tissues. 4. Sanitization – Reduction of microbial population to safe levels. 5. Degerming – Physical removal of microbes from a limited area (e.g., handwashing). 2. Methods of Microbial Control Microbial control methods are broadly classified into: • Physical methods • Chemical methods • Biological methods Control of Microorganisms
- 2. Page | 2 2.1 Physical Methods of Microbial Control Physical methods involve using heat, radiation, filtration, or other techniques to inhibit or kill microbes. A. Heat Methods Heat is one of the most effective and widely used methods for microbial control. It works by denaturing proteins and disrupting membranes. 1. Moist Heat (More effective than dry heat) o Autoclaving (Steam Under Pressure) ▪ Uses 121°C, 15 psi pressure for 15-20 minutes. ▪ Kills all microorganisms, including spores. ▪ Used for sterilizing surgical instruments, culture media, and lab equipment. o Boiling ▪ 100°C for 10-30 minutes. ▪ Kills most bacteria, fungi, and viruses but does not kill spores. ▪ Used for disinfecting water, utensils, and fabrics. o Pasteurization ▪ Mild heat treatment that kills pathogens without destroying food quality. ▪ Types: ▪ LTLT (Low-Temperature, Long Time) – 63°C for 30 minutes. ▪ HTST (High-Temperature, Short Time) – 72°C for 15 seconds. ▪ UHT (Ultra-High Temperature) – 135°C for 1-2 seconds (used for milk). 2. Dry Heat o Hot Air Oven – 160-180°C for 2-3 hours. Used for sterilizing glassware, powders, and oils. o Incineration – Burns waste materials and used in hospitals for biohazard waste. B. Radiation 1. Ionizing Radiation (X-rays, Gamma rays) o Used for sterilizing pharmaceuticals, medical devices, and food. o Breaks DNA strands, leading to microbial death.
- 3. Page | 3 2. Non-ionizing Radiation (UV Radiation) o Causes thymine dimer formation in DNA. o Used for disinfecting surfaces, air, and water. C. Filtration • Used for sterilizing heat-sensitive liquids and air. • HEPA (High-Efficiency Particulate Air) filters – Remove microbes from air. • Membrane filters – Used for filtering bacteria from heat-sensitive fluids. D. Low Temperature & Desiccation • Refrigeration (4°C) – Slows microbial growth. • Freezing (-20°C to -80°C) – Preserves microorganisms but does not kill them. • Lyophilization (Freeze-drying) – Preserves microbial cultures and pharmaceuticals. E. Osmotic Pressure • High concentrations of salt or sugar create a hypertonic environment, leading to microbial dehydration and death. • Used in food preservation (e.g., pickles, jams, salted meats). 2.2 Chemical Methods of Microbial Control Chemical agents are used to disinfect surfaces, sterilize medical instruments, and control microbial growth in various environments. A. Types of Chemical Agents 1. Disinfectants – Used on non-living surfaces. 2. Antiseptics – Used on living tissues. 3. Sterilants – Kill all forms of microbial life, including spores. B. Common Chemical Agents 1. Alcohols (Ethanol, Isopropanol)
- 4. Page | 4 o Denature proteins and disrupt membranes. o Effective at 70% concentration. o Used for skin antisepsis and disinfecting surfaces. 2. Halogens (Chlorine, Iodine, Bromine) o Chlorine – Used in water treatment and disinfectants (e.g., bleach). o Iodine – Used as an antiseptic (e.g., povidone-iodine). 3. Phenolics (Lysol, Triclosan) o Disrupt membranes and proteins. o Used in disinfectants and soaps. 4. Aldehydes (Formaldehyde, Glutaraldehyde) o Cross-link proteins and DNA. o Used for sterilizing medical equipment. 5. Heavy Metals (Silver, Mercury, Copper, Zinc) o Act by denaturing proteins. o Silver nitrate is used in eye drops for newborns. 6. Quaternary Ammonium Compounds (Quats) o Disrupt membranes. o Used in disinfectants and antiseptic wipes. 7. Hydrogen Peroxide & Peracetic Acid o Generate free radicals that damage cells. o Used for sterilizing surfaces and wounds. 2.3 Biological Methods of Microbial Control • Bacteriophages – Viruses that infect and kill bacteria. Used in phage therapy. • Predatory Bacteria (Bdellovibrio bacteriovorus) – Attacks pathogenic bacteria. • Enzymes (Lysozyme, Proteases) – Used in food preservation and antimicrobial treatments. 3. Applications of Microbial Control • Medical Field: Sterilization of surgical tools, disinfection of hospital surfaces. • Food Industry: Pasteurization, food preservatives. • Water Treatment: Chlorination, UV sterilization.
- 5. Page | 5 • Pharmaceutical Industry: Sterile drug manufacturing. • Laboratory Practices: Aseptic techniques, autoclaving culture media. Chemotherapeutic agents are chemical substances used to inhibit or kill microbial pathogens inside a host without harming the host’s cells. These agents are widely used in treating bacterial, fungal, viral, and protozoal infections. They include antibiotics, synthetic antimicrobial drugs, antifungal agents, antiviral agents, and antiparasitic drugs. The term "chemotherapy" was first introduced by Paul Ehrlich, who developed Salvarsan, the first synthetic drug for treating syphilis. 1. Characteristics of an Ideal Chemotherapeutic Agent A good chemotherapeutic agent should have the following properties: • Selective toxicity – Harms the microbe without affecting host cells. • Broad or narrow spectrum – Broad-spectrum drugs act on multiple pathogens, while narrow-spectrum drugs target specific microbes. • Bactericidal or bacteriostatic – Bactericidal drugs kill bacteria, while bacteriostatic drugs inhibit their growth. • Minimal side effects – Should not cause harm to the patient. • Low potential for microbial resistance – Should not easily lead to drug- resistant strains. 2. Types of Chemotherapeutic Agents Chemotherapeutic agents are categorized based on the type of microorganism they target: 1. Antibacterial Agents (Antibiotics & Synthetic Drugs) 2. Antifungal Agents 3. Antiviral Agents 4. Antiprotozoal Agents 5. Antihelminthic Agents