BMB241 Lab Exam 2
name one of the tests that we are doing that will determine glucose fermentation. What would indicate a positive result?
*Glucose fermentation test: + result= yellow color change *MRVP- MR+ red color change; VP+ red color change after reagent addition
Light is lethal to bacteria because it has an effect on the ____ of bacteria.
DNA
UV light is harmful to?
DNA
If you inoculated a mixture of S. aureus and E. coli onto an EMB plate, which would grow and why?
E. coli because it is a gram negative bactera
UV lab results on bacteria:
E. coli= not resistant to light damage 24 hr. B. subtilis= some resistance based on the exposure time 7 day B. subtilis= most resistant due to endospores (still dependent on exposure time)
EMB Agar Test Selective Ingredients
Eosin Y and methylene blue
What does a zone of inhibition indicate?
that the organism is susceptible to the active ingredients in the cleaner
Efficacy
the ability to produce a desired or intended result
Describe how vaccines work to make someone immune to a disease:
the antigens from the disease injected cause an immune response from the body (a small enough dose to not harm us). Antibodies and memory cells are produced by our bodies to recognize and destroy the virus in the future.
Nitrate Test Products
Gas (bubble) and/or blue/black color
Media of Gelatin Hydrolysis Test
Gelatin Agar Slant
What is herd immunity?
When a majority of a population are vaccinated against a disease. This means that even people who have not been vaccinated are less likely to get it because fewer people can catch it from.
Do you think there will be a difference in the effect of UV light on the 24 hour vs. 7 day B. subtilis, why?
Yes, 7 day will contain more endospores which are resistant to UV light (and other environmental stressors)
Starch Hydrolysis Test Enzyme
amylase
Attack Rate
an incidence rate calculated for a particular population for a single disease outbreak and expressed as a percentage
UV light is what type of mutation?
an induced mutation
Aldehyde Effects
attach to amino acids, disrupting protein synthesis
Why does S. aureus on a MSA plate turn yellow?
because it ferments mannitol and produces acid
What is the variable in today's lab with S. marsescens?
the type of DNA repair mechanism (light dependent repair vs. dark repair). Or simply the presence/absence of light during incubation.
Why is it recommended to get an annual flu vaccine?
the virus changing and mutating due to phenomenons like antigenic drift- new strains of the virus
Purpose of Gelatin Hydrolysis Test
to determine whether bacteria can hydrolyze gelatin; to see if it possesses gelatinase
Purpose of Methyl Red Test
to identify organism that are "mixed acid fermenters" and produce stable acid products
Sulfur Test Purpose
to see if cysteine desulfurase is present
Purpose of Nitrate Test
to see if enzyme nitrate reductase is present
Halogen Effects
denatures protein
Motility Test Purpose
determine whether or not an organism is motile
Purple Broth Fermentation Test
determines the fermentation reactions of pure cultures of microorganisms using purple broth. The action of an organism on a carbohydrate substrate results in acidification of the medium detected by a pH indicator dye. Carbohydrate fermentation is a way that some microogranisms produce energy; while some use alternate pathways.
what is one of the characteristics of a microbe that can be determined by the SIM test?
determines the presence of the enzyme thiosulfate reductase, tryptophanase, and motility
Starch Hydrolysis Test
differential test; detects the production of amylase
Influenza Structure
enveloped virus, encapsulated in a capsid, 8 RNA segments
Methyl Red Test Substrate
glucose
EF Agar Test Differential Ingredients
glucose (dextrose) and bromcresol purple
Methyl Red Test Enzyme
glucose metabolism
Disinfection
inactivates pathogens, not all microbes, and not endospores
Indole Test Purpose
indole formation from tryptophan
What is antigenic drift and how does it effect a vaccines efficacy?
it refers to the mutations that change the antibody-binding sites on the virus. Our bodies can no longer effectively recognize and destroy new strands of the disease. In terms of efficacy, it would only be effective if the vaccine were updated to fight off new mutations.
MacConkey Agar Differential Ingredients
lactose and neutral red
EMB Agar Test Differential Ingredients
lactose, eosin Y, methylene blue
Don't forget this step in Gelatin Hydrolysis:
make sure to flood plate with ammonium sulfate and let it sit for 5 minutes
MSA Agar Test Differential Ingredients
mannitol and phenol red
if a microbe has the ability to hydrolyze starch, it can break it down into:
monosaccharides and dissacharides
Nitrate Test Results
negative= clear gas positive= bubble nitrite positive= blue/black
Nitrate Test Media
nitrate broth
Nitrate Test Enzyme
nitrate reductase
MSA Agar Test Results
non-mannitol fermentor= pink mannitol fermentor= yellow
Fatality Rate
number of deaths from a disease per number of infected people
Urease Test Results
pH increase because of a release of ammonia; pH indicator changes from pale yellow to pink when pH increases, indicating a positive Urease test
Urease Test Indicator
phenol red
2 types of flu vaccines in the US
1) inactivated subunit influenza vaccine 2) live attenuated influenza vaccine (via nasal spray)
Effects of UV light on S. marsescens:
1) no effect- confluent pink colonies 2) cell death- fewer pink colonies; will see individual colonies 3) disruption in metabolic pathway- colonies will appear smaller and white because pigmentation (caused by prodigiosin) is disrupted 4) full photoreactivation- regains full red pigment
MSA Agar Test Selective Ingredient
7.5% NaCl
The influenza we used in the epidemiology simulation has a 50% attack rate. If 24 unvaccinated students are exposed how many will become infected?
12 students
The vaccine we used in the epidemiology simulation has a 90% efficacy rate. If 20 students are vaccinated how many will develop immunity?
18 students
When are we covering one of two plates with foil in today's lab?
In the S. marsescens experiment, the dark plate will be wrapped in foil after exposure to UV light.
Methyl Red Test Media
MR-VP broth
Name the selective/differential media we will be working with in today's lab:
MacConkey Agar, Mannitol Salt Agar, EF Media, EMB (eosin y, methylene blue)
Urease Test Product
NH3 (ammonia)
MacConkey Agar Test Results
Positive (ferments lactose)= Hot pink colonies Negative= Colorless Weak fermentor= colorless
Starch Hydrolysis Test Results
Positive: Dark agar with clear zone (zone of hydrolysis) around streak line Negative: Dark agar up to the streak line
Purple Broth Fermentation Test Results
Positive= development of yellow color means carbohydrate fermentation Negative= lack of yellow color, appears purple Gas formation is indicated by the appearance of gas bubbles in the test tube
what type of virus is influenza?
RNA virus (8 single strands); a respiratory virus
SIM Media Test
Sulfide Indole Motility
Photoreactivation
The enzyme photolyase binds to the pyrimidine dimer and cleaves the cyclobutane ring.
Prevalence
The number or proportion of cases of a particular disease or condition present in a population at a given time.
Incidence
The number or rate of new cases of a particular condition during a specific time.
Sterilization
The process that completely destroys all microbial life, including spores.
What must be added to the Nitrate Test to view the results?
Tromsdorff reagent and sulfuric acid in a 1:3 ratio
Urease Test Purpose
Used to differentiate organisms based on their ability to hydrolyze urea with the enzyme urease.
MacConkey Agar Selective Ingredients
bile salts and crystal violet
Sulfur Test positive result
black precipitate
Purple Broth Fermentation Test Media
bromcresol purple
Citrate Test Indicator
bromthymol blue
E. aerogenes gave the following results for the MRVP test- MR-VP+, what type of fermentor is it?
butylene glycol fermentor (turns glucose into pyruvate)
Indole test positive result
cherry red ring
Citrate Test Enzyme
citrate permease and citrase
Gelatin Hydrolysis Substrate
gelatin (protein)
Methyl Red Test Results
positive - red negative - yellow
Citrate Test Results
positive: blue negative: green
Motility Test results
positive: cloudy through out tube negative: cloudy on stab line
Gelatin Hydrolysis Test Results
positive= clear zone around growth negative= no clear area around growth
Nitrate Test Substrate
potassium nitrate
many of the tests we are doing determine the microbe's ability to ferment. What is the product of fermentation?
production of acid or gas
UV damage causes specific mutations in the DNA called?
pyrimidine dimers
UV Light causes
pyrimidine dimers which can kill affected cells
Antiseptic
same as disinfectant, except used on living tissue
EF Agar Test
selective for Enterococcus faecalis and aerotolerant anaerobes
EMB Agar Test
selective for gram negative bactera
MacConkey Agar Test
selective for gram negative enterics
MSA Agar Test
selective for staphylococci and halotolerant bacteria
EF Agar Test Selective Ingredient
sodium azide
Citrate Test Substrate
sodium citrate
Starch Hydrolysis Test Media
starch agar plate
Urease Test Media
urease test broth
Purpose of Citrate Test
used to determine the ability of an organism to use citrate as its sole carbon source
EMB Agar Test Results
weak lactose fermentor= pink strong lactose fermentor= metallic sheen green non-lactose fermenting= no color
What is antigenic shift and how does it relate to vaccine efficacy?
when 2 strains of a virus recombine inside a cell to form a new mutation that changes the antigenicity of the virus. This decreases the efficacy of a vaccine because these shifts in recombination resulting in antigenicity cannot be predicted, so it can lead to a widespread outbreak.
EF Agar Test Results
yellow= glucose fermentor purple= non-fermentor