Micro Lab Exam 3

What is a bacteriophage?

Virus that infects bacterial cells. Core of nucleic acid surrounded by a protein coat

What do bacteriophages infect?

Bacterial cells

What are the life cycles of virulent and temperate phages?

• Lytic cycle (virulent)

  • Adsorption- attachment to the host cell

  • Penetration- transfer of genetic material to host cell

  • Synthesis- host cell synthesizes viral components

  • Maturation- assembly of new viral components

  • Release- host cel bursts and releases phages

• Lysogenic cycle (temperate)

  • Adsorption- “

  • Penetration- “

  • Prophage- host cell incorporates genetic material into chromosome

  • Synthesis and Maturation- assembly of the new viral components

  • Release- host cell bursts and releases phages

What are the steps of viral replication?

• Adsorption- attachment to the host cell

• Penetration- transfer of genetic material to host cell

• Synthesis- host cell synthesizes viral components

• Maturation- assembly of new viral components

• Release- host cel bursts and releases phages

What methods can be used to determine bacteriophage quantity?

Serial Dilutions

How did we quantify bacteriophage quantity in class?

Serial dilution and then poured out onto a plate to count

What are the 4 antibiotics we used in class?

• Penicillin

• Vancomycin

• Erythromycin

• Tetracycline

What method did we use to test antibiotic sensitivity in class?

Disk diffusion

What is the zone of inhibition?

Area around the antibiotic disk that no bacteria grow

How might an antibiotic for Gram-positive bacteria impact peptidoglycan formation?

Penicillin inhibits transpeptidation- formation of peptidoglycan cross-links

Vancomycin blocks construction of the cell wall by targeting where the enzyme binds

Where do nitrogen-fixing bacteria acquire nitrogen?

Air

What nitrogen source did we use in the class media for non-nitrogen fixing bacteria?

Mannitol

What temperature did we incubate the soil bacteria?

23* Fahrenheit (room temperature)

How did we isolate antibiotic-producing bacteria in class?

• Inoculation of nutrient agar plate with soil sample

• isolate antibiotic producing bacteria (streak TSA plate)

• Challenge antibiotic producing bacteria

What are the main bacteria used in yogurt production?

• Streptococcus thermophilus

• Lactobacillus bulgaricus

How does the pH of the milk change as it becomes yogurt?

Drops from 6-4 because it creates lactic acid (becomes more acidic)

What sugars is lactose comprised of?

Glucose and Galactose

What are Koch’s postulates?

1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms

2. The microorganism must be isolated from a disease organism and grown in pure culture

3. The culture microorganism should cause disease when introduced into a healthy organism

4. The microorganism must be reisolated form the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

What are the 3 steps/tests performed during the examination of water lab?

1. Presumptive test

   1. inoculation of lactose broth with a water sample

   2. relative abundance of coliforms

2. Confirmation test

   1. Streak positive lactose broth onto EMB plate

   2. Non-coliform species can also ferment lactose

3. Completed test

   1. inoculation of brilliant green broth from the EMB plate

   2. nutrient agar streak

   3. identifies if isolated colonies can grow in the presence of bile

4. Gram stain-positive brilliant green bile broth colonies

Coliforms ferment what sugar?

Lactose

What is the purpose of using a Durham tube during the water examination lab?

Capture any gas produced

What is MPN? How did we use it to quantify bacteria?

Most probable number. used to estimate concentration of bacteria in a sample

What is the purpose of using EMB agar and brilliant green bile broth?

EMB confirms that coliforms are responsible for fermentation

Green bile broth used to examine coliforms

What did we test using the Snyder agar?

The rate of acid production in our mouths

How can the results of the Snyder’s test determine your susceptibility to tooth decay?

Higher production of acid is related to more tooth decay and dental cavities.