Study Guide For MicroBio

Eyepiece (Ocular Lens)

The lens you look through, typically has a magnification of 10x.

Total Magnification Calculation

Total Magnification = Ocular Lens Magnification x Objective Lens Magnification.

Gram Staining

A method to classify bacteria as gram-positive or gram-negative based on their cell wall structure.

Cocci

Spherical bacteria that may appear as singles, pairs, or clusters.

Negative Staining

A technique to visualize the shape and size of bacteria by staining the background.

Anaerobic Jar

A tool used to create an oxygen-free environment for the growth of anaerobic bacteria.

Thioglycolate Tube

A complex broth that allows for growth of both aerobic and anaerobic organisms.

Selective Media

Media designed to inhibit the growth of some organisms while allowing others to grow.

Differential Media

Media that distinguishes between different types of organisms based on biochemical characteristics.

MacConkey Agar

A selective and differential medium for isolating enteric Gram-negative bacteria.

Mannitol Salt Agar (MSA)

A medium designed to isolate Staphylococcus species and differentiate mannitol fermenters.

Blood Agar

A nutrient-enriched medium that supports a wide variety of bacteria and shows hemolytic activity.

Facultative Anaerobes

Organisms that can grow in both aerobic and anaerobic conditions, like E. coli.

Obligate Anaerobes

Bacteria that thrive in environments without oxygen.

Resolution

The ability to distinguish two close points as separate; higher resolution means clearer images.

Fine Focus Knob

Allows for precise focusing of a specimen once it's in general focus.

Objective Lenses

Lenses found on a rotating nosepiece that are used to observe the specimen at various magnifications.

EMB Agar (Eosin Methylene Blue)

A selective and differential medium that inhibits Gram-positive bacteria and distinguishes between lactose fermenters and non-fermenters based on color changes.

PEA Agar (Phenylethyl Alcohol)

A selective medium that inhibits the growth of Gram-negative bacteria, allowing for the growth of Gram-positive organisms.

Cetrimide Agar

A selective medium for Pseudomonas aeruginosa, which allows for the differentiation of this organism based on its green pigmentation.

Observations on Blood Agar

Shows hemolytic activity; different types of hemolysis (alpha, beta, gamma) indicate different organisms' capabilities to lyse red blood cells.

Mannitol Salt Agar (MSA) Observations

Fermentation of mannitol leads to a color change to yellow, indicating growth of mannitol-fermenting Staphylococcus species.

MacConkey Agar Observations

Lactose fermenters produce pink colonies, while non-fermenters remain colorless, aiding in identification of enteric gram-negative bacteria.

Selective vs Differential Media

Selective media inhibit growth of certain bacteria while differential media indicate differences among organisms based on biochemical reactions.

Lactose Fermenters Examples

Organisms like E. coli and Enterobacter can grow on MacConkey agar, showing pink colonies due to lactose fermentation.

Hemolysis Types on Blood Agar

Alpha hemolysis (partial lysis, green), beta hemolysis (complete lysis, clear), and gamma hemolysis (no lysis).

Pseudomonas aeruginosa Characteristics

Identified on Cetrimide agar by green pigmentation and characteristic colony morphology.