microbio lab quiz 1

microscope transport

Cord wrapped, never dangling

Hand under base, one around the arm

microscope cleaning

Remove oil from lenses and stage

Use lens paper only

microscope storage

Dust cover on

Power on

Lowest setting of light

Go to correct cabinet

microscope components

structural, optical, focusing

structural microscope components

1. Arm

2. Base 

3. Stage

4. Light source

optical microscope components

1. Oculars (usually 10X)

2. Objectives (10X, 40X, 100X oil)

3. Nosepiece

4. Condenser

microscope focusing components

1. Coarse focus

2. Fine focus

total magnification

Ocular x Objective

resolution

Ability to distinguish two close objects as separate

Parfocal

Image stays centered and mostly in focus when switching objectives

Maximizing resolution

1. Use blue filter

2. Raise condenser

3. Open diaphragm

4. Use immersion oil (100X only)

Procedure highlights

1. Use prepared slide

2. Focus on oil immersion

3. Show instructor bacteria

4. Return slide and microscope properly

Troubleshooting checklist

1. Microscope plugged in and on

2. Nosepiece clicked into place

3. Slide specimen side up

4. Adjust light, condenser, diaphragm

5. Pencil wax for specimen

6. Clean oil off 10X and 40X if contaminated

7. Use oil only with 100X objective

fungi characteristics (nucleus, photosynthesis, tissue, cell walls, reproduction, motility)

1. Eukaryotic (true nucleus)

2. Non-photosynthetic

3. No tissue differentiation

4. Cell walls: chitin + polysaccharides

5. Reproduce by spores

6. Non-motile

Fungi forms

mold, yeast, dimorphic

mold descriptions

multicellular, filamentous

mold examples

Penicillium, Rhizopus, Aspergillus

yeast description

Unicellular, budding

yeast examples

Saccharomyces

dimorphic description

can switch between mold + yeast

mold structure

hyphae: mycelium

spore: sporangiospores, conidia

hyphae

Long filamentous strands of growth

Mycelium

A mass of hyphae

Spores

Asexual reproductive units

Sporangiospores

Spores formed inside a sporangium (sac)

Conidia

Free spores formed externally (not in a sac)

Penicillium microscopic ID

conidia in brush-like clusters, paintbrush, broom

Penicillium appearance on plate

 velvety or powdery, blue-green with white border

Rhizopus Microscopic ID

rhizoids (root-like), sporangium (round sac), sporangiospores inside sporangium

rhizopus appearance on plate

fast-growing, fluffy, white turning gray/black as sporangia mature

Aspergillus microscopic ID

conidia arranged around a round vesicle, dandelion puff or lollipop

Aspergillus appearance on plate

powdery, green, yellow, black

yeast structure (cells, reproduction, form…)

1. Unicellular

2. Reproduce by budding

3. May form pseudohyphae (chains of elongated buds)

Saccharomyces Microscopic ID

1. Round to oval budding cells

2. Bud scars may be visible

3. Pseudohyphae possible but not dominant

saccharomyces plate appearance

1. Creamy, smooth, bacteria-like colonies

2. Off-white to beige

Ubiquity definition + examples

1. Bacteria exist everywhere

2. Such as: thermal vents, gut flora, surrounding surfaces

bacteria key characteristics (nucleus, photosynthesis, size)

1. Prokaryotic (no nucleus)

2. Seldom photosynthetic

3. Very small: 0.5-2.0 µm

bacterial growth

1. increase in cell number, not cell size.

2. Exponential: 1 -> 2, 2 -> 4, 4 -> 8

broth growth media (medium, growth signs)

1. Liquid medium

2. Growth appears as turbidity

solid media growth (medium, growth signs)

1. Agar plates or slants

2. Appears as: 

   1. Colonies (individual clumps of cells)

   2. Film (thin layer on surface)

sepsis

presence of bacteria (contamination or infection)

asepsis

absence of bacteria (clean, controlled environment)

sterilization

complete destruction/removal of all microbes and spores

disinfection

eliminates most microorganisms, not necessarily spores

why aseptic technique matters in lab

1. Protects you from infection

2. Prevents contamination of cultures

3. Prevent microorganisms from leaving the classroom

why aseptic technique matters in healthcare

Required for injections, surgery, handling patient samples

flame technique

Heat until red, let cool before touching culture

tube handling (caps and tubes)

1. No caps on table, hold cap with pinky while holding tube, do not hold partners tubes or caps

2. Flame tube mouth before and after inserting loop

Lab rules

1. Each person uses their own burner

2. Incubate all cultures at 37 degrees celsius

3. Discard cultures at end of lab

plate to slant

1. Flame loop

2. Lift plate lid slightly

3. Touch loop to isolated colony

4. Streak slant surface

5. Flame loop

culture types

mixed and pure

mixed culture species + lab

1. 1+ microorganism species

2. In lab

   1. E. coli

   2. Serratia marcescens

   3. Micrococcus luteus

Pure culture reasons for study and composition

1. One species of microorganism

2. Needed to study morphology, metabolism, antibiotic susceptibility

Pure cultures matter b/c:

1. Prevents result misinterpretation

2. Ensures accurate biochemical testing

3. Allows you to link a phenotype to a single organism

4. Critical for clinical diagnostics and research

Streak plate (isolation streak) (technique, dilution, goal)

1. Most common technique

2. Physically dilutes bacteria across agar surface

3. Goal: isolated colonies in final quadrant

subculturing

1. Transfer a single isolated colony to fresh media

2. Purity and fresh growth for testing

isolation technique streak success

1. Incubated upside down

2. Early quadrants: heavy growth

3. Final quadrant: isolated, well-separated colonies

4. Each colony originates from a single cell -> genetically identical

Identifying contamination

1. Unexpected colony colors

2. Irregular shapes/texture

3. Growth in areas you didn’t streak

4. fuzzy/spreading colonies (often mold)

5. Colonies that differ from the known morphology of your organism

E. coli color

gray

Serratia marcescens color

red

Micrococcus luteus

yellow