Microlab Exam #1

(didn't finish pigments)

1 stage micrometer (SU) is equal to how many mm? um?

• 0.01 mm

• 10um

What color is Gram-positive bacteria?

Purple

What color is Gram-negative bacteria?

Pink

Is the peptidoglycan layer thicker in Gram-positive or Gram-negative bacteria?

Gram-positive

What does monotrichous mean?

Has a single flagellum

What does amphitrichous mean?

Has flagella at both ends

What does lophotrichous mean?

Has tuft of flagella at one or both ends

What does peritrichous mean?

Has flagella surrounding the cell

Can the capsule be stained?

No, not directly

What is an endospore?

• A dormant, extremely heat-resistant structure produced by only a few bacterial genera (ex: Bacillus, Clostridium)

• These structures found in cytoplasm

• Resistant to certain chemicals, making difficult to stain

  • Spores extremely dehydrated

  • Water-soluble dyes we use will not penetrate the spore

  • Will be clear areas in Gram stain

• Purpose: to protect cell’s genome from harsh condition

• Capable of being revived after long period of time

Identify the major parts of the compound light microscope & their function

• Eyepiece (ocular lens)

• Camera

• Objective lens

• Stage (slide) clips

• Stage

• Condenser/diaphragm — controls the amount of light that reaches condenser

• Light (source)

• Stage controls

• Course focus

• Fine focus

What is sanitization?

Reduces the number of microbes on a surface to a level that is considered safe according to public health standards

What is disinfection?

Aims to target all microbes on a surface (viruses & bacteria)

What is sterilization?

The complete elimination of all viable microorganisms, including highly resistant forms such as bacterial endospores & viruses

What is subculturing?

• Transferring bacteria from an old culture to fresh broth or agar

• Used to maintain pure stocks of bacteria over long periods of time

What is inoculation?

To transfer bacteria to fresh media

What should be included on your labels for plates & tubes?

• Your name

• Section number

• Date

• Organism name (or number)

• Temperature

What does it mean if a molecule is amphipathic? Is soap amphipathic?

• Each molecule has a hydrophilic polar head region & a hydrophobic nonpolar tail region

• Tail repelled by water but attracted to oils

• Soap is effective bc amphipathic

What are micelles?

• Spherical structures that trap oil, dirt, & microbes inside

• Created by soap molecules when in aqueous environment

• So, soap doesn’t lyse/kill bacteria but simply removes them from skin surface

Hand sanitizers with concentrations of alcohol higher than __ have decreased efficacy, but they must have at least __ alcohol to be effective.

• 90%

• 60%

What are fastidious bacteria?

Bacteria that require additional growth factors or specific nutrients to support growth & therefore require supplemented media

What is chemically defined media?

All chemical components & their exact concentrations are known

What is complex media?

• Some ingredients are naturally derived (ex: extracts & digests) & their precise chemical composition is unknown

• Ex: TSA, NA

What are the steps of Gram staining & what is used for each step?

• (1) Primary stain (crystal violet) — all cells look purple

• (2) Mordant (iodine) — all cells remain purple

• (3) Decolorizer (ethanol) — only Gram-positive cells remain purple; Gram-negative cells become colorless

• (4) Secondary stain (safranin) — Gram-positive remain purple; Gram-negative cells become pink

Crystal violet → iodine → ethanol → safranin (CIES)

What are the different forms for bacterial morphology?

• Punctiform

• Circular

• Rhizoid (root-like)

• Filamentous (thread-like)

• Irregular

• Spindle

What are the different margins for bacterial morphology?

• Entire

• Undulate (wavy)

• Lobate (finger-like)

• Curled (concentric circles)

• Filamentous (thread-like)

• Erose (serrated)

**if a colony’s margin does not fit into one of these classifications it can be considered irregular

What are the different elevations for bacterial morphology?

• Flat

• Raised

• Convex

• Umbonate

• Pulvinate

• Crateriform

Mesophiles grow best at temperatures between __ & __

20 degrees C & 45 degrees C

Psychrophiles cannot grow above __ but can survive in environments below __

• 20 degrees C

• 0 degrees C

Thermophiles grow best at temperatures between __ & __

45 degrees C & 80 degrees C

What is optical density?

The light waves are scattered as they pass through the culture sample, with more scattering as density increases

What bacteria is prodigiosin associated with & what are the characteristics of this pigment?

• Serratia marcescens

• Red in color

• Opt. temp: room temp. (30 degrees C)

• Has potential antibiotic & cancer-fighting properties

• Source of natural coloring for food industry

• Increases effectiveness of sunscreen

What bacteria is pyocyanin associated with & what are the characteristics of this pigment?

• Pseudomonas aeruginosa

• Responsible for chronic & persistent infections in cystic fibrosis & cancer patients, skin infections in burn patients, hot tub rash, & swimmer’s ear

• Blue-green phenazine pigment

• Below pH of 5 will turn red