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