Lab Fundamentals Skills 1 & 2, Ubiquity/Description, Staining

What is the definition of aseptic in laboratory setting?

without contamination of the culture, the sterile medium or surroundings.

What is the definition of aseptic in clinical setting?

Free of contamination from pathogens.

What is the purpose of a streak plate? (quadrant streak)

The bacterial cell density decreases, leading to growth of individual colonies. Each colony started as one cell.

What does CFU stand for?

Colony-forming unit

What is the purpose of a simple zigzag inoculation?

Same as quadrant streak.

Why is it good to have a control ?

To be able to compare to other results. Helps establish a baseline in experiments.

Coccus

Spherical

Bacillus

Straight rod

Coccobacillus

Oval

Spirillum

Long, wavy rod

Vibrios

Slightly curved rod

Spirochete

Spiral

Pleomorphic

Oddly shaped, not one shape.

Diplo-

Pairs

Strepto-

Chains

Staphylo-

Random clustering

Tetrad

2 × 2 square

Sarcina

2 × 2 × 2 cube

Staphylococcus epidermis

Crystal violet

Bacillus subtilis

Safranin

Micrococcus luteus

Methylene blue

Simple stain

Stain organism to increase contrast, background remains clear. Includes methylene blue, crystal violet, safranin.

Negative stain

Stains background leaving organism clear. “nigrosin”

Gram positive

About 90% peptidoglycan, stains purple or blue.

Gram negative

Cell wall contains about 10% peptidoglycan and 90% lipid polysaccharides. Stains pink or red.

Are eukaryotic cells Gram positive or Gram negative ?

Gram negative

How do you calculate total magnification?

Objective magnification x Ocular magnification

How do you calculate limit of resolution?

D= wavelength \ Na condenser + Na objective

Describe limit of resolution.

How close two objects in the field of view can get before they blur together.

How does Gram Staining work?

1. All cells initially stain purple because of crystal violet.

2. Adding iodine causes formation of crystal violet- iodine complexes. Cells are still purple.

3. Decolonization involves addition of an alcohol/acetone mix.

4. Counter staining with safranin will stain all decolorized cells pink.