Session 9: Controlling Microbial Growth In Vitro

Vocabulary flashcards based on Session 9 notes on controlling microbial growth in vitro, covering environmental factors, specialized culture media, hemolysis, and physical and chemical control methods.

Desiccation

Complete drying in which certain microbial stages (such as bacterial endospores and protozoan cysts) survive in a dormant state and resume growth when returned to a moist environment.

Thermophiles

Microorganisms that thrive at high growth temperatures, such as those found in hot springs and hydrothermal vents.

Mesophiles

Microorganisms that grow best at moderate temperatures, including normal human body temperature ($37^\circ\text{C}$).

Psychrophiles

Microorganisms that thrive in cold environments, such as cold ocean water and snow.

Psychroduric Organisms

Microorganisms that prefer warmer temperatures but are capable of surviving and enduring extreme frozen states.

Acidophiles

Microorganisms that prefer acidic environments ($\text{pH } 2$ to $5$), thriving in stomach acid, pickled foods, hydrothermal vents, and coal mining debris.

Alkaliphiles

Microorganisms that thrive in alkaline environments ($\text{pH } 8.5$ or higher), such as the human intestine ($\text{pH } 9$), carbonate-laden soils, and soda lakes.

Crenation

The shrinkage of a human red blood cell caused by the loss of water when placed in a hypertonic solution.

Plasmolysis

The shrinkage of a bacterial cell's cytoplasm caused by water loss when placed in a hypertonic solution.

Hemolysis

The swelling and bursting of a human red blood cell caused by water flowing inward when placed in a hypotonic solution.

Plasmoptysis

The swelling and escape of cytoplasm from a bacterial cell caused by water flowing inward when placed in a hypotonic solution.

Halophilic Microbes

Microorganisms that actively thrive in high-salt environments.

Haloduric Organisms

Microorganisms that do not prefer salty environments but are fully capable of surviving and enduring in them.

Piezophiles

Microorganisms that thrive under very high atmospheric pressure, such as in deep ocean waters or oil wells.

Obligate Aerobes

Microorganisms that require an atmosphere similar to humans (approx. $20\%$–$21\%$ $O_2$ and $78\%$–$79\%$ $N_2$) to survive.

Microaerophiles

Microorganisms that require oxygen for growth, but in significantly reduced concentrations (around $5\%$ $O_2$).

Obligate Anaerobes

Microorganisms that are killed or completely inhibited by the presence of oxygen.

Capnophiles

Microorganisms that require increased concentrations of carbon dioxide for optimal growth (typically $5\%$–$10\%$ $CO_2$).

Bacterial Growth

The proliferation or multiplication of bacterial cells rather than an increase in the size of individual cells.

Binary Fission

The asexual reproduction process by which a single bacterial cell divides to form two cells.

Generation Time

The amount of time required for a particular bacterial species to undergo binary fission.

Fastidious Organisms

Microorganisms that are difficult to isolate or grow in laboratory settings because they require highly complex, specific nutrients.

Chemically Defined Medium

A culture medium in which all ingredients and their precise gram measurements are known.

Complex Medium

A culture medium with an undefined composition containing digested or ground-up extracts from animal organs, fish, yeasts, or plants.

Agar

A complex polysaccharide obtained from red marine algae used as a solidifying agent in culture media.

Enriched Medium

A broth or solid culture medium supplied with extra rich nutrients to support the growth of fastidious organisms.

Blood Agar

An enriched and differential growth medium consisting of nutrient agar plus $5\%$ sheep red blood cells.

Chocolate Agar

A rich brown growth medium containing nutrient agar and powdered hemoglobin, used to culture fastidious pathogens like Neisseria gonorrhoeae and Hemophilus influenzae.

Selective Medium

A culture medium formulated to discourage the growth of certain organisms without inhibiting the organism being sought.

Differential Medium

A culture medium used to visually distinguish between different types of microorganisms growing on the same plate.

MacConkey Agar

A culture medium that inhibits Gram-positive bacteria, selecting for Gram-negative bacteria, and differentiates lactose fermenters from non-lactose fermenters.

Alpha ($\alpha$) Hemolysis

Partial breakdown of red blood cells on blood agar, forming a green or brown ring around bacterial colonies due to hemoglobin leaking and converting to methemoglobin.

Beta ($\beta$) Hemolysis

Complete breakdown and destruction of red blood cells on blood agar, producing a clear zone around and under the colonies.

Gamma ($\gamma$) Hemolysis

The complete absence of red blood cell breakdown (non-hemolytic) around colonies growing on blood agar.

Mannitol Salt Agar (MSA)

A selective and differential medium containing high salt concentrations that screens for Staphylococcus aureus by turning from pink to yellow upon mannitol fermentation.

Thioglycollate Broth (THIO)

A liquid medium used in bacteriology that supports the growth of all bacterial categories, from obligate aerobes to obligate anaerobes.

Sabouraud Dextrose Agar (SDA)

A specialized growth medium used primarily to isolate and cultivate fungi, including yeasts, molds, and dermatophytes.

Aseptic Technique

Laboratory practices designed to prevent infection of personnel and avoid contamination of clinical specimens, culture media, and the work environment.

Sterilization

The complete destruction or elimination of all microbial life, including vegetative cells, endospores, and viruses.

Disinfection

The removal or destruction of most or all pathogens (excluding bacterial endospores) from nonliving objects.

Pasteurization

A process that disinfects liquids using heat to eliminate pathogens from beverages like milk.

Disinfectants

Chemical solutions applied to nonliving inanimate objects to kill pathogens; they are not sporicidal and are harmful to living tissue.

Antiseptics

Specialized chemical solutions safe for application to skin and living tissues to disinfect them.

Sanitization

The reduction of microbial populations on inanimate objects to levels deemed safe by public health standards.

Bactericidal Agent

A chemical or physical agent that directly kills bacteria, though not necessarily their endospores.

Sporicidal Agent

An agent specifically capable of killing bacterial endospores.

Microbiostatic Agent

An agent that inhibits the reproduction and growth of microorganisms without necessarily killing them.

Bacteriostatic Agent

An agent that specifically inhibits bacterial metabolism and cellular reproduction.

Lyophilization

A preservation procedure combining dehydration and freezing in a vacuum to keep microbes in an inactive state.

Sepsis

The presence of pathogenic microorganisms or their toxins in blood or living body tissues.

Asepsis

The complete absence of pathogenic microorganisms.

Thermal Death Point

The lowest temperature required to kill all organisms in a standard pure culture within a specified time period.

Thermal Death Time

The length of time required to completely sterilize a pure culture at a specified temperature.

Incineration

A dry heat sterilization method that uses burning to destroy contaminated disposable materials.

Autoclave

An apparatus resembling a large pressure cooker that uses steam under pressure to completely destroy all microbial life.