bio 120 chapter 11

microorganism has permanently lost its ability to reproduce under suitable conditions

microbial death

Destroys or removes all forms of microbial life, including viruses and endospores

ex. Autoclaving surgical instruments

sterilization

Destroys most vegetative pathogens on inanimate objects or surfaces. Does not necessarily destroy bacterial endospores.

ex. disinfecting a countertop

disinfection

Physically removes microbes from a limited area.

ex. cleaning skin with an alcohol wipe

degerming

Reduces microbial numbers to levels considered safe by public health standards.

ex. sanitizing dishes

sanitization

Kills microorganisms.

ex. a treatment that kills bacteria

microbiocidal

An agent that kills microbes; the name may specify the target organism.

ex. a bactericide kills bacteria

germicide

Inhibits microbial growth without necessarily killing the organisms.

ex. bacteria stop multiplying while the agent is present

microbiostatic

Applying chemical agents called antiseptics to living tissues, wounds, or incisions to destroy or inhibit vegetative pathogens.

ex. antiseptic skin cleanser

antisepsis

microbial contamination or growth in tissues or the body, often associated with infection.

ex. infection involving tissues

sepsis

Absence of significant contamination by disease-causing microbes.

ex. maintaining sterile technique

asepsis

The shortest time required to kill all microbes in a sample at a specified temperature under defined conditions.

ex. determining how long heating must last

thermal death time

the lowest temperature that kills all microbes in a sample in 10 minutes under defined conditions.

ex. comparing heat resistance

thermal death point

what are the four categories/ targets for antimicrobials

cell wall, cell membrane/cytoplasm, DNA/RNA, proteins

how cell wall is affected by antimicrobials

Agents can block cell wall synthesis, digest the wall, or break down its surface. A damaged cell wall makes the cell fragile, so it can lyse (burst) easily

how cell membrane/cytoplasm is affected by antimicrobials

The membrane contains lipids and proteins.

the cell loses selective permeability, vital molecules leak out, and damaging chemicals can enter.

how proteins are affected by antimicrobials

Microbial cells depend on proteins to function. Agents can denature proteins or inhibit ribosomes, stopping protein synthesis.

how DNA/RNA is affected by microbials

Agents can interfere with DNA replication, DNA transcription, or change the genetic code. This disrupts normal cell functioning.

surface-active substances that reduce surface tension and help liquids spread across surfaces.

bind to the lipid layer of the membrane and penetrate its hydrophobic region. create leaky spots, allowing damaging chemicals to enter and ions to leave.

surfactants

These agents kill or inactivate microorganisms.

cidal

Germicide/microbicide: Kills microorganisms.

Bactericide: Kills bacteria, except those in the endospore stage.

Fungicide: Kills fungal spores, hyphae, and yeasts.

virucide: Inactivates viruses.

sporicidal: Capable of killing endospores.

These agents prevent microbes from multiplying but do not necessarily kill them.

static

Bacteriostatic: Prevents bacterial growth.

fungistatic: Inhibits fungal growth.

microbiostatic: Chemicals used to control microorganisms in the body, including antiseptics and drugs.

physical methods to control bacterial growth

heat, cold, filtration, radiation, and osmotic pressure, with heat divided into moist and dry methods

how moist heat (boiling water, pasteurization, and steam under pressure) controls growth

Uses hot water, boiling water, or steam. temperature range of approximately 60°C–135°C.

affects proteins.

Mechanism: Coagulation and denaturation of proteins

proteins lose their normal shape and function, stopping important cellular processes and potentially killing the cell.

what method of moist heat causes disinfection; kills vegetative cells and viruses, but not bacterial endospores.

boiling

what method of moist heat reduces spoilage organisms and pathogens in beverages while maintaining food quality

pasteurization

what method of moist heat uses steam under pressure to sterilize, targets proteins and essential components; kills microorganisms, including endospores.

autoclaving

how dry heat controls growth

Uses heated air or a flame, generally at temperatures above 160°C

affects the cellular materials are damaged through oxidation.

dehydrates and oxidizes cellular components.

the cell is damaged and killed- burning cells to ashes.

ex. bunsen burner, direct flame

how cold treatment can affect growth

low temperatures slow microbial activity.

affects cellular metabolism and the processes needed for growth.

slow metabolic reactions and microbial activity.

Microbial growth slows or stops temporarily. generally does not sterilize or kill all microorganisms.

mainly bacteriostatic — it stops or slows growth rather than reliably killing all microbes

gamma rays and X-rays.

high-energy waves that can be used for disinfection or sterilization, especially for materials that cannot tolerate heat.

affects nucleic acids, especially DNA; other cellular structures can also be damaged.

produces highly reactive ions, causing DNA mutations

causes DNA damage can prevent normal replication and cell function, leading to microbial death.

ionizing radiation

ultraviolet (UV) light.

used to reduce airborne microbes and sanitize surfaces, drinking water, pools, laboratories, and operating rooms.

affects DNA.

UV light causes abnormal bonds called pyrimidine dimers between adjacent DNA bases, including thymine and cytosine

DNA replication and transcription are disrupted, preventing normal cell function and potentially killing microbe.

non-ionizing radiation

membrane filters and HEPA filters.

air or liquid passes through a filter that captures microorganisms.

no specific cell structure is targeted; the microbes are physically trapped or removed.

physical separation rather than chemical damage.

the air or liquid is decontaminated because microorganisms have been removed from it.

used in hospitals, laboratories, and homes. filter bacteria, allergens, fungi, and some large viruses.

filtration

curing meat with salt and preserving jams or jellies with sugar.

large amounts of salt or sugar create a hypertonic environment around the bacteria.

affects the cell's water balance and the cell membrane.

water moves out of the bacterial cell into the surrounding environment.

cell shrinks away from its cell wall, a process called plasmolysis. The bacteria cannot multiply normally.

High salt or sugar → water leaves the cell → plasmolysis → growth is inhibited.

osmotic pressure

three conditions for autoclaving

15 psi (pounds per sq inch), 121 degrees, 15-20 mins