Labs 9-12

Question 1

Spore Staining

Answer 1

Endospores are not easily penetrated by stains:

• Heat applied while staining with malachite green, not removed by subsequent washing with decolorizing agents or water
• Heat (mordant) helps pigment penetrate deeper inside of the cell

Question 2

Endospore Locations

Answer 2

• Central
• Terminal (either end)
• Lateral (side)
  Knowing if these are present helps in classifying and identifying certain types of bacteria (Bacillus, Clostridia)

Question 3

Wet Mount Preparation

Answer 3

• Place a drop of liquid, onto or containing specimen, onto microscope slide
• Touch the liquid with the edge of a coverslip, holding slip at a 45 degree angle
• Drop coverslip onto the slide
• Useful for viewing still-living organisms; easy to prepare

Question 4

Brownian Motion (Streaming)

Answer 4

Water molecules are colliding with another material or an organism, giving it the appearance of movement (shaking or vibrating due to water current)

Question 5

True Motility

Answer 5

• In microbes, due to flagella or cilia
• From a medical standpoint, knowing this tells the medical staff whether an infectious agent is localized or capable of spreading

Question 6

Presence of Flagella

Answer 6

This increases the ability of bacteria to cause disease because it allows them to go wherever they want, spreading the disease as they go

Question 7

Monotrichous

Answer 7

Single flagellum at one end

Question 8

Amphitrichous

Answer 8

Single flagellum at each end

Question 9

Lophotrichous

Answer 9

A tuft of many flagella at one end

Question 10

Peritrichous

Answer 10

Flagella located on many sides

Question 11

Arrangement of Flagella

Answer 11

This helps microbiologists characterize and classify bacteria

Question 12

Complex (nutrient) Medium

Answer 12

Contains rich extracts of meat or plants that supply amino acids, nucleotide bases, vitamins, and other growth factors; exact composition and amounts are not known; used to cultivate an organism with unknown nutritional requirements

Question 13

Defined Medium

Answer 13

Specific nutritional requirements for an organism to grow are known, so the specific chemical composition of this medium are also known; individual components are weighed out exactly

Question 14

Liquid (broth) Cultures

Answer 14

Used to grow large volumes of bacteria

Question 15

Agar

Answer 15

Used to isolate colonies on a solid medium:

• First used by Robert Koch
• Melts at 100’ C and solidifies at 45’ C
• Cannot be used as an energy source by most bacteria
• 1.5% concentrations to solidify (.4% for motility studies)
• Sterilized using an autoclave: media heated to 121’ C for at least 15 minutes at 15 psi of steam pressure

Question 16

Colony Characteristics

Answer 16

• Configurations
• Margins
• Elevations
• Color: S. marcescens - red; S. epidermidis - white