Physical and Chemical Control Lecture Notes

Flashcards covering vocabulary for physical and chemical microbial control methods, including sterilization goals, thermal processes, radiation effects, and chemical categories.

Sterilization

The most intense strategy that eliminates all life from an environment, including bacteria, protists, viruses, and dormant endospores.

Disinfection

The destruction of vegetative (active) organisms from a non-biological surface, usually through a chemical process.

Decontamination/Sanitization

The removal of vegetative cells and hazardous materials from non-biological surfaces to create a safe environment, critical in food processing and clinical settings.

Antisepsis/Degermation

The reduction of microbial load on biological surfaces using less-hazardous chemicals or lower concentrations of chemicals.

Microbicidal (Bactericidal)

Methods of control that actually kill the targeted microbes.

Microbiostatic (Bacteriostatic)

Methods of control that stop microbes from functioning or growing (stasis) without killing them.

Dry Heat

A physical control method that dehydrates the cell, causing it to shrivel and lose enough moisture to die.

Incineration

A dry heat method where cells are exposed to temperatures high enough to completely oxidize them into ash, such as a Bunsen burner flame at $1,870^{\circ}C$.

Moist Heat

A control method that causes proteins to denature by changing the structure of the active site so it loses the ability to function.

Boiling

A moist heat method used for disinfecting water where $30$ minutes at $100^{\circ}C$ kills most vegetative cells, but not spores.

Pasteurization

The use of less-than-boiling heat to partially disinfect liquids like milk or juice to kill pathogens and spoilage organisms without ruining the product.

Autoclaving

A sterilization method using high pressure to raise the steam point of water to $121^{\circ}C$, which is capable of killing endospores.

Hot-air ovens

Devices that use gas or electrical coils to heat air to $150$-$200^{\circ}C$ to desiccate organisms.

Lyophilization

A process using cold temperatures and drying to 'freeze-dry' cells, which can be used to keep them alive long-term.

Ionizing radiation

A physical control method that uses electromagnetic waves to create charged particles in the cell, causing widespread damage.

Non-ionizing radiation

A method using electromagnetic waves that creates mutations in DNA, specifically Thymine Dimers where a covalent bond forms between adjacent thymine bases.

Halogens

Elements from Group 17, such as Chlorine and Iodine, that denature enzymes and disrupt cellular function or metabolism.

Hypochlorous Acid $HOCl$

The compound created when bleach reacts with water; it denatures enzymes and disrupts cellular function.

Oxidizing Agents

Highly electronegative chemical compounds, like Hydrogen Peroxide ($H_2O_2$), that steal electrons and can form free radicals ($OH^-$) to react with DNA and proteins.

Phenolic Compounds

Aromatic compounds containing a hydroxyl group, such as Triclosan and Triclocarban, which disrupt cell walls, membranes, and proteins.

Alcohols

Short carbon molecules with a hydroxyl ($OH$) group, like Ethanol or Isopropanol, which dissolve cell membranes at concentrations above $50\%$.

Detergents

Amphipathic molecules, such as Quaternary Ammonium compounds or Sodium lauryl sulfate, that act as surfactants to disrupt cell membrane surface tension.