Lab Exam 3

avatar
Created by
Keylie Moore

Cards (183)

  • Where must virus and eukaryotic virus work be conducted?
    Biosafety cabinets with high level of sterility
  • What is a bacteriophage?
    viruses that ONLY infect bacteria
  • What are the characteristics of Bacteriophage?
    -requires bacterial host to replicate
    -does NOT have enzymes or ribosomes
    -contains DNA
    -COMPLEX structure
  • What are the characteristics of Animal Viruses?
    -requires a eukaryotic cell host to replicate
    -does NOT have enzymes or ribosomes
    -contains either RNA or DNA (not both)
    -SIMPLE structure
  • What function do animal virus and bacteriophage share?
    they lyse the host cells (eukaryotic or bacteria)
  • What are the steps of the virus cycle?
    -Attachment
    -Penetration
    -synthesis
    -Assembly
    -Release
  • Why is soft agar used in Plaque Assay of Virus Titer?
    -consistency is firm enough that the bacteria can't move through it but NOT firm enough to let the bacteriophage move short distances so that the bacteriophage can infect neighboring bacterial cells
  • What is the definition of a formation of Plaque?

    the area of clearing on the bacterial lawn, is the result of a bacteriophage infecting and destroying bacterial cells
  • What happens in the tube with only bacteria in Plaque Assay of Viruses?
    -Plate is covered in lawn of bacteria
    -No phage so no bacteria destroyed
  • What happens in the tube with more phage than bacteria in Plaque Assay of Viruses?
    No lawn since all bacteria is destoryed
  • What happens in the tube with more bacteria than phage in Plaque Assay of Viruses?
    plaques are formed
  • When a phage that infected the bacterial cell lyses the cell and releases the phage, what is required for the new phages to infect other cells?
    cells with direct contact with the lysed cells
  • What is the concentration of a bacteriophage sample given in?
    Plaque-forming units per mL (PFU/mL)
  • What is the formula for calculating the PFU/mL?
    (# plaques)/(dilution factor)(mL of phage added to bacteria)
  • What causes a stippled effect and what does it mean?
    -Having more phage than bacteria
    -lysis of all bacteria
  • What causes a lawn of bacteria in Plaque Assay of Virus?
    no phage
  • What is Urea?

    the product of the decarboxylation of certain amino acids
  • What is Urease?

    an enzyme present in certain bacteria that can hyrolyze (break down) urea into ammonia (NH3) and CO2
  • What is the process of Urea hydrolysis?
    Urea + H2O --(urease)->2NH3 +CO2
    -alkaline compound produces a HIGH PH
  • What are the ingredients for Urea Broth?
    -TRACE amounts of yeast extract (nutrient)
    -Urea (substrate for enzyme)
    -Potassium phosphate buffer (strong enough to maintain neutral pH UNLESS large amounts of alkaline compounds are present)
    -Phenol Red indicator
  • What is the starting color of Urea broth and the pH level?
    Peach; roughly 6.8
  • What is a positive Urease result?
    media turns pink due to high pH
  • What is a negative Urease result?
    media remains peach or turns slightly yellow in color
  • What are the characteristics of coliforms?
    -gram negative rods
    -can FERMENT LACTOSE with GAS production within 48 hours of growth at 37C
    -generally associated with fecal material
    -most common coliform; E. coli
  • What is the coliform used to indicate in a water sample?
    Fecal contamination
  • What is the Multiple Tube Fermentation Method aka?
    Most Probable Number (MPN)
  • What are the two things MPN allows one to calculate?
    -TOTAL coliform counts in water sample
    -E.coli counts in water sample
  • What is the objective of the MPN experiment?
    To determine whether water from these 2 duck pond sites is contaminated with coliforms and specifically E. coli and if there are differences in the level of contamination between these 2 sites. All this will be done by calculating the MPN.
  • What is contained in Lauryl Tryptose Broth (LTB)?
    -Lauryl sulfate (inhibits growth of orgs. other than coliforms)
    -lactose (fermentation)
    -durham tube (gas)
  • What is LTB media selective for?
    coliforms and gives presumptive determination of presence of coliforms
  • After 48 hours of incubation, LTB broths are observed for?
    -Growth
    -presence of gas
  • Tubes that contain probable coliforms show what on day 3?
    growth and possible gas at top of durham tube
  • on day 3, if the LTB media produces growth, what are the two broths you inoculate 2 loops of media in?
    -Brilliant green lactose bile broth (37C for 48 hours)
    -e. coli broth (45C for 48 hours)
  • What is contained in Brilliant Green Lactose Bile Broth (BGLB)?
    -lactose (sugar source)
    -Durham tube (gas)
    -2% bile (inhibits non-coliforms)
  • BGLB is what type of media and what does it do?
    a selective media and confirms the presence of coliforms
  • On day 5 of MPN, what are the BGLB broths examined for?
    presence of gas
  • ON day five of MPN, tubes that contain coliforms will show what in the tube of BGLB media?
    gas (aka positive)
  • What are day 5 BGLB media tubes used to determine if they contain gas?
    total coliform counts
  • What are the ingredients in E.coli broth?
    -lactose
    -durham tube
    -bile salts
  • E. coli media is what type of media and what is it helping to produce when grown at 45C?
    selective; selective for E. coli