Lab 21
Viruses that infect bacterial cells
What are bacteriophages
A substance produced by a microorganism that is antagonistic to the growth of other microorganisms at a high concentration
What is antibiotic
Bacteria that grow on only mannitol plates in the absence of peptone
What are nitrogen-fixing bacteria
Diseases are caused by microorganisms
What is the germ theory
A coliform is used to detect whether water is suitable for drinking
What is Escherichia coli
Host cells are lysed rapidly after phage assembly.
What is the lytic cycle
An antibiotic produced by the fungus Penicillium notatum
What is penicillin
Bacteria in soil may produce antibiotics to do the following
What is competition for resources and nutrients
____________ formulated the germ theory of disease and ____________ provided concrete evidence.
What are Louis Pasteur and Robert Koch
Steps in coliform-based bacteriological test
What are presumptive test, confirmed test, and completed test
Techniques used for the assessment of bacteriophage-host interaction.
What are pour plate and serial dilution
An antibiotic that inhibits the binding of bacterial tRNA to the ribosome.
What is Tetracycline
As the bacteria in yogurt grow, they use the milk sugar lactose as an energy source and produce ________.
What is lactic acid
_________ is an example of a disease identified by Robert Koch to be caused by a pathogenic bacterium.
What is Anthrax or Tuberculosis or Cholera
Media used in confirmed test is _________. While that used in completed test is __________.
What are EMB plate and Bile medium
# of plaques/ Volume of bacteriophage transferred x Final dilution
What is PFU/mL
A clear circular area around the disc is impregnated with antibiotics in which the bacteria colonies do not grow.
What is zone of inhibition
In an MBRT milk quality test, _____ milk losses the blue color in less than 2 hours.
What is poor milk
Example of an exception for Koch's postulate
Some diseases (like pneumonia) may be caused by multiple types of bacteria (so it is impossible to fulfill the first postulate)
Some bacteria (like Streptococcus pyogenes) cause a variety of different diseases (may not cause the same disease when introduced to new host, so it is impossible to fulfill postulate 3)
Some diseases are in humans only (like HIV)(can’t feasibly fulfill postulate 3, as “introducing into a healthy organism”
The statistical method used to estimate the viable numbers of bacteria in a sample by inoculating broth in 10-fold dilutions is based on the principle of extinction dilution. It is often used in estimating bacterial cells in water and food.
What is the most probable number (MPN)
This form of bacteriophage is harmless to the host cell and is part of the lysogenic cycle.
What is prophage
A large zone of inhibition around an antibiotic disc means the bacterium is _________ to the antibiotic. While no zone of inhibition around the disc means the bacterium is __________ to the antibiotic.
What is susceptible
What is resistant
The process eliminates some milk contaminating bacteria and reduces the CFU/mL of milk.
What is pasteurization
The third Koch postulate
What is a microorganism isolated from a diseased host must cause the same disease symptom when introduced into a healthy host.
What is the MPN of this water sample?
Three out of five 0.1 mL water lactose tubes are positive
Two out of five 1 mL water lactose tubes are positive
One out of five 10 mL water lactose tubes is positive
What is 17