Microbiology: Control Methods, Growth Requirements, and Staining Techniques

Vocabulary flashcards covering microbial heat treatments, growth temperature classifications, oxygen requirement categories, endospore staining reagents, and acid-fast staining components.

Sterilization / commercial sterilization

Destroys all microorganisms on the surface of solid items or in fluid (ex: autoclaving).

Pasteurization

Heat-treatment process that destroys microorganisms in certain foods and beverages, treated with mild heat, usually to less than $100\,^{\circ}\text{C}$.

Tyndallization

Heating the substance to boiling point and holding it there for $15\,\text{minutes}$, three days in succession, where the resting period allows surviving spores to germinate into bacterial cells that are killed by the next day's heating.

Sanitization

Lowering the number of germs to a safe level (ex: sanitizing procedures for restaurants or dishwashers).

Minimum temperature

Minimum temperature below which enzymes will not function.

Optimal temperature

The temperature where the enzyme works best.

Maximum temperature

Maximum temperature where enzymes function.

Psychrophiles (psychrotrophs)

Organisms that can grow at low temperature ($5\,^{\circ}\text{C}$ or below).

Mesophiles

Organisms that can grow at mid-range temperature ($30\,^{\circ}\text{C}$ to $37\,^{\circ}\text{C}$).

Thermophiles

Organisms that can grow at high temperature (Above $50\,^{\circ}\text{C}$).

Prodigiosin pigment

Pigment whose synthesis involves enzymes affected by temperature; pigment production is activated at lower temperatures (temperature-regulated phenotype).

Obligate (strict) aerobes

Organisms that need $O_2$ to grow.

Obligate anaerobes

Organisms that cannot grow with $O_2$.

Facultative anaerobes

Organisms that can grow with or without $O_2$, but grow better with $O_2$.

Aerotolerant anaerobes

Organisms that do not require $O_2$ and have the same growth with or without $O_2$.

Microaerophiles

Organisms that require low $O_2$ to grow.

Fluid thioglycollate medium (FTM)

Culture medium that has a reducing agent which reduces oxygen to water to get rid of it.

Resazurin

An oxygen indicator that turns purple in the presence of oxygen.

Endospores

Specialized 'resting cells' that form during adverse conditions; present terminally, sub-terminally, or centrally, and are dormant and unable to reproduce.

Clostridium spp. & Bacillus spp.

Important genera that form endospores; Bacillus spp. is involved in the food industry (food spoilage), clinical settings (hard to kill endospores, requiring autoclaving), and contamination in microbiology labs.

Spore staining

A differential stain used to detect endospores; difficult due to the spore coat outside the cell.

Malachite green

Primary stain in endospore staining that stains endospores green when heat is applied to enter the endospores.

Water

Serves as the decolorizer for endospore staining.

Safranin

Counterstain for endospore staining that stains vegetative cells red.

Acid-fast organisms

Bacteria that resist decolorization by acids during staining because their cell walls contain a thick, waxy lipid called mycolic acid (ex: Mycobacterium tuberculosis, M. leprae, Mycobacterium smegmatis).

Mycolic acid

Thick, waxy lipid in the cell walls of acid-fast bacteria that refrains water-soluble stain from entering the cell and makes them resistant to desiccation, chemicals, and antibiotics.

Carbolfuchsin

Phenolic compound and lipid-soluble stain that can penetrate acid-fast stained cells like Mycobacterium red.

Acid-alcohol

Used as a decolorizer in acid-fast staining.

Methylene blue

Counterstain in acid-fast staining that can stain non-acid-fast stained cells like Staphylococcus blue.