LAB QUIZ 2 part 1

Colony Morphology

Only on isolated colonies [Physical appearance of colonies (shape, edge, elevation) on a plate]

Bacterial Cell Morphology

Microscope observations of individual cells or how those cells cluster together- Bacillus, Streptococcus, Coccus, etc

[Shape and arrangement of individual cells under a microscope (SIZE, TEXTURE]

Difference between colony vs cell morphology

Colony morphology refers to the physical appearance of bacterial colonies on a plate, including their shape, edge, and elevation, while cell morphology describes the shape and arrangement of individual bacterial cells observed under a microscope.

Coccus (Cocci)

Perfect Circle-shaped bacteria

Cocci/ Coccus

Bacilli/ Bacillus

Elongated rod (Also called Rods)

Bacilli/ Bacillus

prefixes

Diplo: groups of two

Strepto: cells in a chain

Staphylo: cells in a cluster (many togather)

diplococci

Streptococci

ci

Staphylococci

Gram stain

A staining method used to classify bacteria

Gram staining steps

1. Make smear

2. Stain with Crystal Violet: Stains Peptidoglycan

3. Iodine (mordant):Fixes stain to cells in a complex that cannot be removed

4. Alcohol (decolorization): removes non-binded crystal violet

5. Water rinse: remove alcohol

6. Stain with Safranin: Counter stain, stains everything:

7. Blot and observe:Phase contrast or Bright Field?

Mordant

A chemical that helps stain stick (iodine)

Counterstain

Second stain that colors remaining cells

Gram-positive

Purple (keeps crystal violet) because thick cell wall keeps stain

Gram-negative and why it color

Pink/red (loses purple, takes safranin) because thin cell wall loses stain

Bright Field Microscopy uses and best for

1.) uses

• Uses transmission (light passing THROUGH something) of light through the objective lens

• Image appears dark on a bright background

2.) best for:

• Non living (Inanimate) objects

• Stained or pigmented cells (mostly dead) Because staining adds contrast

• ⚠ Not good for live cells (they are too transparent)

Memory tip:

“Bright background → need stain to see things”

Bright Field Microscopy

Phase Contrast Microscopy uses and best for

1.) uses

Uses differences in refractive index

(how much light bends when it goes through something) between bacteria and environment

2.) best for

Living and Unstained cells

Shows internal details more clearly

Memory tip:

“No stain → still see live cells”

Phase Contrast Microscopy

Is colony morphology the same as cell morphology?

NO

Which step fixes stain to cells?1.)

1.)Iodine (mordant)

Which step removes stain

Alcohol

What does “staphylo” mean?

Clusters

What did the bacteria grow on? (plate, broth, slant)

Media

Which step acts as the mordant in Gram staining?” (Translation: Which step locks the stain?)

Iodine

What is the counterstain in Gram staining?

( Translation: What is the second stain?)

Safranin

The difference of Mordant vs Iodine AND Counterstain vs Safranin

Mordant And Counterstain → the job (Function: what it does)

Iodine And Safranin → the chemical (what it is, the actual substance)

What is the mordant in Gram staining?

Iodine

What is iodine’s role?

Mordant

What is the counterstain?

Safranin

What is the role of safranin?

Counterstain

coccus

Staphylococcus

Streptobacillus