Applied Microbiology SCH2235 Practical Skills Test Prep

A comprehensive set of vocabulary flashcards based on the Practical Skills lab content for applied microbiology, covering definitions of techniques, reagents, and organism classifications.

Aseptic technique

Procedures used in the laboratory to prevent contamination of cultures, samples, people, and the environment.

Sterilisation

The complete destruction of all microorganisms on an object or surface.

Smear

A thin film of bacterial cells spread on a microscope slide for staining and viewing.

Heat fixing

The process of passing a slide quickly through a flame to kill bacteria, attach them to the slide, and preserve cell shape.

Simple stain

A staining procedure that uses a single primary dye, such as methylene blue, to increase contrast and make bacteria visible.

Resolution

The ability of a microscope to distinguish detail or the ability to separate two close points.

Oil immersion

The use of a specific liquid with the $100\times$ objective lens to reduce light refraction and improve image clarity.

Motility

The ability of a microorganism to move independently using its own power.

Brownian motion

The random vibration of microscopic particles or cells caused by collisions with water molecules.

Gram-positive

Bacteria characterized by a thick peptidoglycan layer that retains crystal violet stain, appearing purple or violet.

Gram-negative

Bacteria characterized by a thin peptidoglycan layer and an outer membrane that lose crystal violet during decolourisation and take up safranin, appearing pink or red.

Mordant

A chemical, such as iodine, that fixes a dye in a cell by forming an insoluble complex.

Decolouriser

A substance like alcohol or acetone used in differential staining to remove the primary stain from certain cells.

Colony morphology

The physical appearance and characteristics of bacterial colonies on an agar plate, such as size, shape, margin, and elevation.

Pure culture

A laboratory culture containing only a single species of microorganism.

Isolated colony

A single, separated cluster of bacteria on an agar surface that originates from a single bacterial cell.

Haemolysis

The breakdown or destruction of red blood cells by bacterial enzymes.

Beta haemolysis

Complete destruction of red blood cells appearing as a clear zone around a bacterial colony on blood agar.

Alpha haemolysis

Partial breakdown of red blood cells appearing as a green or brown discolouration on blood agar.

Gamma haemolysis

A result on blood agar indicating no breakdown of red blood cells and no change in the media appearance.

Acid-fast bacteria

Organisms like Mycobacterium that contain waxy mycolic acid in their cell walls, resisting decolourisation by acid-alcohol.

Mycolic acid

A waxy lipid layer found in the cell walls of acid-fast bacteria that provides a hydrophobic barrier.

Capsule

A gel-like outer polysaccharide coating surrounding some bacteria that protects against phagocytosis and increases virulence.

Negative stain

A technique that stains the background rather than the bacterial cells, often used to visualize capsules as clear halos.

Obligate Aerobes

Microorganisms that require oxygen to grow.

Facultative Anaerobes

Microorganisms that can grow with or without oxygen, though they usually grow better in its presence.

Obligate Anaerobes

Organisms that cannot survive in the presence of oxygen because it is toxic to them.

Psychrophiles

Bacteria that grow best in cold temperatures.

Mesophiles

Bacteria that grow best at moderate temperatures, typically between $20\,^{\circ}C$ and $45\,^{\circ}C$, including most human pathogens.

Thermophiles

Bacteria that thrive at high temperatures.

Plasmolysis

The shrinking of bacterial cells caused by water leaving the cell via osmosis when placed in a high-salt environment.

Fastidious organism

An organism that has complex nutritional requirements and needs specifically enriched media to grow.

Selective media

Media designed to inhibit the growth of certain bacteria while allowing others to grow, such as MacConkey agar or Mannitol Salt Agar.

Differential media

Media that allows the distinction between different types of bacteria based on visible reactions, such as lactose fermentation or haemolysis.

API 20E

A standardized biochemical identification strip used to identify Gram-negative enteric bacteria.

Catalase

An enzyme that breaks down hydrogen peroxide into water and oxygen, causing bubbling during a positive test.

Coagulase

An enzyme that converts fibrinogen to fibrin, causing plasma to clot; used primarily to identify Staphylococcus aureus.

Oxidase

An enzyme involved in the electron transport chain of aerobic respiration; detected to help identify Pseudomonas and Neisseria species.

Quality Assurance (QA)

A system of procedures designed to prevent defects or problems in laboratory processes.

Quality Control (QC)

The active process of detecting defects or errors, such as using known control organisms to check stain performance.

Enterobacteriaceae

A large family of Gram-negative enteric bacilli that are typically oxidase negative.

Zone of inhibition

The clear area around an antimicrobial disc where bacterial growth has been prevented.

CLED agar

Cystine Lactose Electrolyte Deficient agar, a medium used for urine cultures to support pathogens and prevent the swarming of Proteus species.

Broad spectrum antibiotic

An antimicrobial medication effective against a wide range of both Gram-positive and Gram-negative bacteria.

Narrow spectrum antibiotic

An antimicrobial medication that targets only specific groups of bacteria.