Microbiology: Germ Theory and Sterilization

The process of killing or inactivating harmful microorganisms in food, especially in canning.

The process of reducing the number of viable microbes on a living surface, like skin or mucous membranes.

The process of removing or neutralizing harmful substances, including microbes, from a surface or object.

The process of completely eliminating all forms of microbial life, including spores.

The theory that states microorganisms cause many diseases.

The process of reducing the number of viable microbes on inanimate objects or surfaces.

A chemical agent used to carry out disinfection.

A chemical substance that inhibits the growth of microorganisms on living tissue.

A process that uses high temperatures (121°C) and pressure to kill all microorganisms, including spores.

Low temperatures like refrigeration and freezing slow down the growth rate of microorganisms.',

The removal or reduction of microorganisms from a surface, typically by scrubbing or washing with soap or other cleaning agents.

The process of cleaning and reducing the number of microorganisms to a safe level, often in food handling, water treatment, or public health contexts.

A suffix indicating the killing of a specific type of microorganism.

A suffix indicating the inhibition or slowing down of microbial growth.

Inanimate objects or surfaces that can harbor and transfer infectious microorganisms, like doorknobs or countertops.

The concentration of the agent, temperature, time of exposure, microbial characteristics, and presence of organic matter.

Microbial control agents can disrupt the cell membrane, causing leakage of vital substances and cell death. Examples include detergents.

Agents like penicillin inhibit cell wall formation, leading to osmotic pressure changes and cell lysis. Bacteria without cell walls are less susceptible.

Heat or chemicals can denature proteins, disrupting their function and cellular processes. This happens by breaking bonds, making proteins useless.

Radiation or chemicals can damage DNA or RNA, preventing replication or transcription, halting cell division and potentially leading to cell death.

Heat (dry and moist), filtration, radiation, desiccation, and low temperatures.

Heat kills microorganisms by denaturing proteins, disrupting cell membranes, and damaging nucleic acids. Higher temperatures are more effective.

Dry heat involves higher temperatures (e.g., ovens) and works by oxidizing cellular components. Moist heat uses steam or water vapor and is typically more effective.

Pasteurization uses moderate heat to kill pathogens and reduce the number of spoilage microorganisms in food without harming taste or quality.

High pressure (100 to 800 MPa) can kill or inhibit the growth of microorganisms by affecting their cell membranes, enzymes, and DNA.

A method of testing disinfectants by measuring the number of microbes that survive a specific exposure time.

Chemicals used to kill or inactivate microorganisms on surfaces or objects.

A type of chemical disinfectant that can kill bacteria and enveloped viruses, often used on skin and surfaces.

Powerful disinfectants, like formaldehyde and glutaraldehyde, used for sterilization, particularly in medical settings.

Disinfectants like chlorine and iodine used for water purification, surface cleaning, and wound care.

Disinfectants derived from phenol, effective against diverse microbes including bacteria, fungi, and viruses.

A type of chemical compound with a hydrophilic (water-attracting) and hydrophobic (water-repelling) part, often used in detergents and disinfectants.

Surfactants that reduce the surface tension of water, used in cleaning and disinfecting applications.

Detergents with a positively charged hydrophilic head that can disrupt the cell membranes of microorganisms.

Detergents with a negatively charged hydrophilic head primarily used for cleaning, with lower effectiveness against microbes.

Disinfectants containing negatively charged ions with an acidic pH, commonly used for sanitizing food processing equipment.

Heavy metals like mercury, silver, and copper that can inhibit microbial growth by binding to proteins and enzymes within microbes.

Silver ions can kill bacteria by binding to their cellular components, interfering with their functions.

Copper ions damage bacterial cell membranes and proteins, disrupting their essential functions.

Chlorine is a halogen used to disinfect drinking water, swimming pools, and surfaces.

Chlorine releases chlorine gas (Cl₂) or hypochlorite ions (OCl⁻), which are highly reactive and can inactivate enzymes and proteins in microorganisms.

Iodine is a halogen used as an antiseptic and disinfectant, typically in the form of iodine tinctures or povidone-iodine.

Iodine penetrates microbial cells and binds to amino acids and proteins, disrupting their function and structure.

Ethanol and isopropanol are commonly used as disinfectants for skin, surfaces, and in laboratory settings.

Alcohols denature proteins and dissolve lipids, disrupting cell membranes and leading to cell leakage and death.

Essential oils, like tea tree oil, eucalyptus oil, and lavender oil, are plant-derived compounds with natural antimicrobial properties.

Essential oil compounds, such as terpenes, phenols, and aldehydes, can disrupt cell membranes, inhibit enzyme function, and alter protein structure in microorganisms.

Formaldehyde and glutaraldehyde are highly effective chemical disinfectants used to control microbial growth.

Aldehydes cross-link the amino and sulfhydryl groups in proteins, nucleic acids, and other macromolecules in microbial cells.

Sodium nitrate/nitrite, sorbic acid, benzoic acid, and calcium propionate are commonly used as food preservatives.

Chemical preservatives lower the pH of the food, interfere with microbial metabolism, or disrupt their cell membranes.

They control microbial growth, increasing shelf life and are generally considered safe for consumption within regulated limits.

Chemicals that release oxygen upon breakdown, used for disinfection and antisepsis. Examples include hydrogen peroxide and peracetic acid.

They release oxygen radicals, damaging microbial DNA, proteins, and lipids, leading to cell death. Effective against anaerobic bacteria, viruses, and fungi.

Substances used to kill or inhibit the growth of microorganisms (bacteria, viruses, fungi, parasites).

Penicillin prevents bacteria from synthesizing cell walls, weakening them and causing them to burst due to pressure.

Tetracyclines and aminoglycosides bind to bacterial ribosomes, preventing protein synthesis, vital for microbial growth.

Polymyxins bind to and disrupt the bacterial cell membrane, making it leaky and causing cell death.

Rifampin and quinolones block DNA or RNA synthesis, inhibiting replication and transcription, essential for microbial growth.

Sulfonamides block enzymes involved in folic acid synthesis, necessary for nucleic acids and proteins, disrupting microbial metabolism.

A type of antimicrobial drug derived from natural sources or synthesised in the lab, specifically used to treat bacterial infections.

Microorganisms evolve mechanisms to resist antibiotics that once killed them or inhibited their growth, through mutation, gene transfer, and selective pressure.

Bacteria can pass on antibiotic resistance through conjugation (direct DNA transfer via pilus), transformation (uptake of free DNA), and transduction (transfer by a virus).

The complete destruction of all forms of microbial life, including bacterial spores, using heat, chemicals, or radiation.

The process of eliminating most or all pathogenic microorganisms on a surface or object, not necessarily spores, using chemicals or heat.

The reduction of microbial load on living tissues, usually through the application of antimicrobial agents.

The removal of microorganisms from a surface, usually through mechanical action or the application of antiseptic agents.

The larger the zone, the more effective the antimicrobial agent is.

Halogens like chlorine and iodine work by oxidizing microbial proteins and DNA, leading to cell death.

Alcohols are good at denaturing proteins and dissolving lipids in bacterial cell membranes.

Quaternary ammonium compounds disrupt cell membranes, causing leakage of cellular contents.

Antiseptics are used on living tissues to reduce the number of microorganisms, while disinfectants target inanimate surfaces.

Soaps are used for degerming, detergents are for cleaning and disinfection, and emulsifiers help suspend oils and fats in solutions.

Glutaraldehyde is a high-level disinfectant effective against most microorganisms, including bacterial spores. It's non-corrosive, broad-spectrum, and long-lasting.

Bacterial spores are highly resistant to many disinfectants and require more intense treatments, while vegetative bacteria are generally easier to kill but vary in their resistance.

Enveloped viruses are more susceptible to disinfectants than non-enveloped viruses.

The type of microbe, concentration of the agent, temperature, time of exposure, and presence of organic matter all influence the effectiveness of microbial control agents.

The mechanism by which a microbial control agent works to disrupt the structure of a cell and kill or inhibit its growth.

The cell wall provides structural integrity and helps regulate the cell's internal environment. Disruption weakens the cell and can lead to lysis (bursting) or inability to control its internal environment.

The cell membrane controls the passage of molecules in and out of the cell. Disruption causes leakage of essential cellular contents, leading to cell death.

Denaturation of proteins inactivates enzymes and other essential proteins vital for cell function. This can be caused by heat or chemicals.

DNA and RNA are responsible for replication and transcription, which are essential for microbial growth and reproduction. Damage to these molecules halts these processes.

Moist heat uses steam or water vapor and is generally more effective at lower temperatures than dry heat because it transfers heat more efficiently.

Boiling water at 100°C can kill most bacteria, viruses, and fungi but not spores. Boiling for 10-30 minutes can kill most vegetative forms, but resistant spores may survive.

Autoclaving uses steam under pressure at high temperatures (121°C or higher) to kill all microorganisms, including spores. It's the most effective method for sterilization.

Pasteurization uses heat to kill pathogens and reduce spoilage microbes in liquids like milk and juice without affecting taste or quality. There are two types: High-Temperature Short Time (HTST) and Ultra-High Temperature (UHT).

Dry heat sterilization uses hot air at temperatures ranging from 160°C to 170°C for 2 to 3 hours. It kills microorganisms by oxidizing cellular components and dehydrating the cell. It requires higher temperatures and longer exposure times than moist heat.

Filtration physically removes microorganisms from liquids and air by passing them through a filter with pores small enough to trap microbes. It's used for sterilizing heat-sensitive liquids and purifying air.

Low temperatures slow down the growth and reproduction of microorganisms by reducing metabolic rate. While freezing may kill some, psychrophiles can still grow at low temperatures.

High pressure processing (HPP) uses pressures up to 1000 MPa to disrupt cellular structures like membranes and proteins. It's a non-heat method for killing microbes in food.

Desiccation removes water from cells, inhibiting microbial growth, as water is essential for metabolic processes. Freeze-drying (lyophilization) is used to preserve microorganisms.

Osmotic pressure creates a high concentration of solutes (e.g., salt or sugar) outside the cell, which draws water out of the cell, leading to plasmolysis and inhibiting growth.