Microbiology Lab final 2065, SLCC Microbiology Lab Final Review

selective media

isolate specific groups of bacteria, inhibit growth of one and permit growth of another

phenylethyl alcohol agar

isolates gram-positive organisms

crystal violet agar

selective for gram-negative microorganisms

7.5% sodium chloride agar

selective to halophilic microorganisms

detects member of Staphylococcus

differential/ selective media

distinguishes between morphological and biochemical groups of organisms

chemicals change how the growth or medium around growth appear

mannitol salt agar

7.5% of NaCl which inhibits most bacteria

mannitol which allows some staphylococci to ferment

(both permit staphylococci) yellow zone is present

MacConkey agar

crystal violet inhibits gram-positive

carbohydrate lactose tests enteric bacilli

coliform bacilli

produce acid due to lactose fermentation- red bacteria

lots of acid produced leads to pink halo

dysentery, typhoid, and paratyphoide bacilli

do not produce acid

tan colonies, sometimes transparent

eosin-methylene blue agar (Levine)

E. coli is blue/black with shiny green

enterobacter aerogenes make thick pink, mucoid colonies

inhibits gram-positive

non fermenting lactose appears purple

enriched media

media that is very nutritious with blood, serum, yeast extract

cultivates fastidious organisms

blood agar

5-10% sheep or horse blood

gamma hemolysis

no lysis of red blood cells

no significant change in medium around colonies

alpha hemolysis

incomplete lysis of red blood cells

results in green halo around bacterial growth

common with streptococci pneumoniae

beta hemolysis

lysis of red blood cells

clear halo around colonies

common with streptococcus pyogenes

Embden-Meyerhof (glycolytic) pathway

1 mole glucose to 2 moles of pyruvic acid

Krebs cycle

carbohydrate fermentation

Durham- tube nutrient broth, carbs as substrate to determine fermentative capabilities, pH indicator phenol red (acid turns it yellow)

detects gas production

glucose, pyruvic acid, acetyl-CoA, krebs cycle, citric acid and oxaloacetic acid and a-ketoglutaric acid, amino acids

aerobic pathway

oxygen is final electron acceptor

fermentation

used when electron transport chain is unusable, turns NADH and pyruvate into NAD+ and an organic molecule, not as efficient at producing ATP

anaerobic pathway

inorganic ions are final electron acceptor, no oxygen

catalase

enzyme that breaks hydrogen peroxide to water and oxygen

prevents oxidation

catalase test

positive when hydrogen peroxide on bacteria results in bubbles

this means there is catalase in the bacteria because oxygen is being released

IMViC

four tests of differentiation of enterobacteriaceae:

indole

methyl red

Voges-Proskauer

citrate utilization

superoxide dismutase

enzyme that changes the radical superoxide into either normal oxygen or hydrogen peroxide, used when catalase is not present

what gas can be produced in carbohydrate fermentation in Durham tube

CO2

2 possible fermentation results

C3 C3 lactic acid in animals

CO2 CO2 C2 C2 alcohol in plants and most organisms

Kovac's reagent

detects presence of indole

makes a cherry red layer if indole is present

tryptophan is converted to indole?

MR-VP broth

used in methyl red & Voges-Proskauer test

peptones, buffers, and glucose

methyl-red indicator

reagent that detects presence of large concentrations of acid end products

pH of 4 turns red: positive result, glucose is fermented

pH of 6 turns yellow: negative result

Barritt's reagent

in VP test, alcoholic a-naphthol and 40% potassium hydroxide solution

dark rose color is + result, acetylmethylcarbinol is present and glucose was fermented

Simmons Citrate agar

made of citrate, amonium ions, other ions

detects if microorganism can use citrate as an energy source

positive result is blue

negative result is green

enterobacteriaceae

in intestinal tract

gram-negative

non-spore-forming bacilli

pathogens in intestines

salmonella

shigella

occasional pathogens in intestines

proteus

klebsiella

normal intestinal flora

escherichia

enterobacter

SIM agar

contains substrate tryptophan

is used in Indole test of IMViC

Indole production test of IMViC

Kovac's reagent is added to SIM agar with tryptophan to see if red layer is produced.

If it does, there is indole present!

Methyl red test of IMViC

differentiates between E. coli & E. aerogenes

Voges-Proskauer test of IMViC

tests organisms' ability to produce neutral end products

uses Barritt's reagent

Citrate Utilization test of IMViC

some microorganisms use citrate for energy instead of glucose

uses Simmons citrate agar to detect presence of citrase

mycology

study of fungi

mycelium

vegetative part of a fungus or fungus-like bacterial colony, consisting of a mass of branching, thread-like hyphae.

vegetative mycelium

It is the portion which absorbs nutrients.Does not produce spores.

aerial mycelium

It is the portion connected with asexual reproduction.

Produces asexual spores.

hyphae

each of the branching filaments that make up the mycelium of a fungus

how are molds identified

mycelium, spores, species

size of yeast compared to bacteria

Larger

Blood agar

nutrient enriched media used to identify hemolytic enzymatic organisms

Blood agar

Streptococcus sanguis (sanguinis)

+ Growth, α -hemolysis

Blood agar

Staphylococcus aureus

+ Growth, ß -hemolysis

Blood agar

Staphylococcus epidermis

+ growth, gamma-hemolysis

Phenylethyl Alcohol (PEA)

This medium is used for the isolation of the most gram-positive organisms. It is partially inhibitory to gram-negative organisms which may form visible colonies whose side and number are much smaller then on other media

Phenyl ethyl Alcohol (PEA)

Escherichia coli

- (growth inhibited)

Phenyl ethyl Alcohol (PEA)

Staphylococcus

+ growth

Mannitol Salt Agar (MSA)

This medium is inhibitory to most organisms other then the halophilic (salt loving) microorganisms.

Mannitol Salt Agar (MSA)

Escherichia coli

+ growth, + fermenter

indicates a change of media color to yellow around colony growth

Mannitol Salt Agar (MSA)

Staphylococcus epidermis

+ growth, - fermenter

no change in media color

Mannitol Salt Agar (MSA)

Streptococcus

- (growth inhibited)

too high salt concentration

MacConkey Agar

Enterobacter aerogenes

+ growth, + fermenter

Media shows growth, lactose fermentation due to red/pink colorization on colony surface

MacConkey Agar

Escherichia coli

+ growth, + fermenter

Media shows growth, lactose fermentation due to red/pink colorization on colony surface

MacConkey Agar

Staphylococcus

- (growth inhibited)

Eosin-Methylene Blue Agar

Escherichia coli

+ growth, + rapid fermenter

colony is blue-purple-black with metallic green sheen

Eosin-Methylene Blue Agar

Enterobacter aerogenes

+ growth, + slow fermenter

colony is think, mucoid, pink-red colorization

Eosin-Methylene Blue Agar

Staphylococcus

- (growth inhibited)

Lactose Fermentation

Alcligenes faecalis

no fermentation

Lactose Fermentation

Escherichia coli

Acid with gas

Lactose Fermentation

Staphylococcus epidermidis

Acid

Dextrose (glucose) Fermentation

Alcligenes faecalis

No fermentation

Dextrose (glucose) Fermentation

Escherichia coli

Acid with gas

Dextrose (glucose) Fermentation

Staphylococcus epidermidis

Acid

Sucrose Fermentation

Alcligenes faecalis

No fermentation

Sucrose Fermentation

Escherichia coli

Acid with gas

Sucrose Fermentation

Staphylococcus epidermidis

Acid

Catalase Test

Staphylococcus aureus

+ bubbling on surface when add H₂O₂

Catalase Test

Staphylococcus epidermis

+ bubbling on surface when add H₂O₂

Catalase Test

Lactococcus lactis

- no bubbling on surface when add H₂O₂

Indole Production Test

Enterobacter aerogens

neg

Indole Production Test

Escherichia coli

positive

Indole Production Test

Klebsiella pneumoniae

neg

Methyl Red test

Enterobacter aerogenes

Neg

Methyl Red test

Escherichia coli

Positive

Methyl Red test

Klebsiella pneumoniae

neg

Voges-Proskauer test

Enterobacter aerogenes

positive

Voges-Proskauer test

Escherichia coli

neg

Voges-Proskauer test

Klebsiella pneumoniae

Positive

Citrate Utilization Test

Enterobacter aerogenes

Postive

Citrate Utilization Test

Escherichia coli

Neg

Citrate Utilization Test

Klebsiella pneumoniae

Positive