CH 2 Test Review Flashcards
(13 cards)
Five I’s of Studying Microorganisms
Inoculation: Introducing microorganisms into a culture medium.
Incubation: Maintaining microorganisms at a suitable temperature for growth.
Isolation: Separating a single type of microorganism from others to obtain a pure culture.
Inspection: Observing the physical characteristics of the microorganisms (e.g., shape, color, size).
Identification: Determining the species of microorganisms using various techniques (e.g., biochemical tests, molecular methods).
Types of Cultures (Media)
Defined (Synthetic) Media: Media with known and precise chemical composition (e.g., glucose, nitrogen salts).
Complex Media: Media with components of unknown composition (e.g., beef extract, yeast extract).
Selective Media: Contains substances that inhibit the growth of certain microorganisms while encouraging the growth of others (e.g., MacConkey agar).
Differential Media: Contains substances that allow the identification of microorganisms based on their metabolic products (e.g., blood agar, which shows hemolysis).
Enriched Media: Media that contains additional nutrients to support the growth of fastidious organisms (e.g., chocolate agar).
Agar – What it Is & Why We Use It
What It Is: A gelatinous substance derived from red algae, commonly used as a solidifying agent in culture media.
Why We Use It: Agar does not melt at body temperature and remains solid at the temperatures used for culturing microorganisms, providing a stable medium for growing and isolating colonies.
Differential Media
Definition: Media, contains substances that allow the differentiation of microorganisms based on their appearance, due to metabolic activities.
Examples:
Blood Agar
MacConkey Agar
Parts of the Light Microscope
Eyepiece (Ocular Lens): Where you look through to view the sample; usually has a 10x magnification.
Objective Lenses: Lenses of varying magnifications (4x, 10x, 40x, 100x).
Stage: Platform where the slide is placed.
Condenser Lens: Focuses light onto the specimen.
Diaphragm: Adjusts the amount of light passing through the specimen.
Coarse and Fine Adjustment: Focus the image at different resolutions.
Arm and Base: Support the microscope.
Types of Microscopes
Brightfield Microscope: The most common type, using light to view specimens against a bright background. Limited resolution for smaller microorganisms.
Phase-Contrast Microscope: Enhances contrast without the need for staining, allowing visualization of live cells and their structures.
Fluorescence Microscope: Uses UV light to excite fluorescent dyes that bind to specific cellular structures.
Electron Microscope (EM): Uses electron beams instead of light for high magnification and resolution (scanning EM and transmission EM).
Resolution vs. Contrast
Resolution: The ability to distinguish two points as separate. Higher resolution means finer details are visible.
Contrast: The difference in light intensity between the object and the background. Good contrast helps distinguish details in a specimen.
Magnification
Enlarging the appearance of an object.
Total Magnification = Ocular Lens Magnification × Objective Lens Magnification.
Methods of Plating
Streak Plate: A method for isolating a pure culture by spreading a diluted sample over the surface of the agar plate.
Pour Plate: Dilute the sample in agar and pour it into a Petri dish, where colonies grow both on the surface and throughout the agar.
Spread Plate: The sample is spread over the surface of the agar using a sterile spreader to isolate colonies.
Inoculation Tools
Inoculating Loop: A small, wire loop used to transfer microorganisms to a culture medium.
Inoculating Needle: Similar to a loop, but used for stabbing into the agar to grow microorganisms under anaerobic conditions.
Sterile Swabs: Used for collecting samples from surfaces, bodies, or environments.
Pasteur Pipette: A tool for transferring liquids or small volumes of media.
Reasons for Staining
Improve Contrast: Staining enhances the visibility of cellular structures.
Identify Organisms: Certain stains can reveal specific features, such as Gram-positive vs. Gram-negative bacteria.
Highlight Structures: Staining allows for the observation of structures like cell walls, nuclei, and endospores.
Differentiate Cells: Some stains help identify different types of microorganisms or differentiate between pathogenic and non-pathogenic organisms.
Results of Plating & Incubation
Colony Morphology: After incubation, colonies may have specific characteristics like color, size, and shape, which help in identifying the microorganism.
Growth Patterns: Fast-growing organisms appear as large, dense colonies, while slower-growing or more fastidious organisms may require longer incubation.
Temperature & Oxygen Preferences: Some microorganisms need specific environmental conditions (e.g., anaerobes grow in oxygen-free environments).
Growth of Fastidious Bacteria
Definition: Fastidious bacteria are organisms that have complex nutritional requirements and are difficult to grow in standard laboratory conditions.
