question

How can you improve a microscopes resolution

answer

by decreasing d (the resolution) by lowering the wavelength or increasing the numerical aperture.

question

Diplococci

answer

divide in one plane
(pairs)

question

Streptococci

answer

divide in one plane
(chains)

question

Tetracocci

answer

Divide in two planes
(Tetrads, square shape)

question

Staphylococci

answer

divides in 3 planes irregularly
(clusters)

question

Sarcinae

answer

divide in 3 planes regularly
(cuboidal packets, diamond shape.)

question

Gram -

answer

PINK

question

GRAM +

answer

PURPLE

question

Cationic dyes

answer

basic
+
methylene blue/crystal violet

question

anionic dyes

answer

acidic
-
acid fuschin/congo red/nigrosin

question

Fat Soluble dyes

answer

No charge
sudan black, stains granules of polyB-OH-butyric acid

question

Insoluble dyes

answer

Water insoluble
India Ink
colloid suspension of carbon particles

question

Negative staining

answer

stains back ground, not the cell.
uses nigrosin and india ink.
good for telling cell size

question

simple stain

answer

one dye stains all cells the same color
used to tell morphology or size.
(negative staining is better for finding size)
uses methylene blue OR crystal violet

question

Name the two types of differential staining

answer

Gram stain & Acid-fast stain

question

Gram stain

answer

Stains cells differently based on their cell wall.
Stain with crystal violet, fix with iodine, rinse with alcohol, and then counterstain with saffranin.

question

Acid fast stain

answer

stains based on characteristics of cell wall
Acid-fast cells have a high content of wax in their cell wall which requires us to use steam to penetrate them.
steamed while adding carbol fuschin, add acid alcohol to decolorize, then counter stain with methylene blue.
AF + = red
AF - = blue

question

Name the 2 genre of acid fast organisms

answer

Mycobacterium & Nocardia

question

Name the two important species of Mycobacterium

answer

Tuberculosis and Leprae

question

Natural Media

answer

media composed of raw materials whose chemical composition is unknown.
(nutrient agar)

question

Synthetic media

answer

Media whose exact chemical composition is known and in many instances is designed for isolation, selection or differentiation of specific types of microorganisms.

question

Name the two types of synthetic media

answer

Selective & differential

question

Selective media

answer

favors growth of one type of microorganism over another. (inhibits unwanted growth or enriches conditions preferred by the desired organism)

question

Differential media

answer

Distinguishes between types of microorganisms based on differences in appearance of growth or color changes.

question

(PEA) Phenylethyl Alcohol Agar

answer

Selects for growth of GRAM + microorganisms.
(Phenyl Alcohol inhibits growth of GRAM -)

question

(DES) Desoxycholate Agar

answer

Selects for GRAM -
Desoxycholate agar inhibits growth of GRAM +
Differentiates for lactose fermentors
Fermentors appear red
Non fermentors DO NOT appear RED

question

(EMB) Eosin Methylene Blue

answer

Selects for Gram -
Differentiates lactose +/- organisms
(lactose + have color change, lactose - do not)
differentiate between amounts of acid. (Mixed and butanediol)

question

Mixed Acid Fermenter

answer

product of (EMB)
These produce more acid and produce colonies with blue/black centers.(center is almost the size of the entire colony)
E. coli produces a metallic green "sheen" after this test.

question

Butanediol Fermentor

answer

Produce less acid so the colonies have pale pink to lavender centers. (center is very small, like a bullseye)
Does not have a metallic green sheen.
(enterobacter)

question

Blood Agar

answer

Differentiates based on reactions to blood.
Beta hemolysis - Complete blood hemolysis. (clearing around colony)
Alpha hemolysis - Partial blood hemolysis.
(partial clearing around colony, sometimes appears green due to partial reduction of hemoglobin in blood)
Gamma hemolysis - No blood hydrolysis
(no zone of clearing around colony)

question

Biochemical tests

answer

Tests used to determine physiological characteristics of microorganisms in terms of bacterial enzymes and the chemistry of biooxidation.

question

Starch Agar

answer

Tests for presence of Amylase.
(amylase hydrolyses starch into simple sugars)
Iodine is added to plate around colonies, and appears blue/black when reacting with starch. If amylase is present the starch will be hydrolyzed and blue/black color will not be seen around the amylase positive communities.
(+ result = NO blue/black color around colonies)

question

Milk Agar

answer

Tests for presence of Caseinase.
(Caseinase hydrolyses casein into amino acid products.)
(Casein is the predominant protein in milk)
(Casein also what gives milk its white color)
A breakdown of casein causes the milk plate to lose its white color and become clear around the caseinase positive colonies.
(+ result = clearing around colonies)

question

Lipase Plate

answer

Tests for the presence of lipase.
(lipase hydrolyses fat to for glycerol and fatty acids)
The production of the fatty acids lowers the pH enough to produce a dark blue precipitate when a microorganism is lipase +
(Clear ring around colony with a dark blue parcipitate around it.)
Soaks up the color.

question

Sugar Fermentation Tubes

answer

Used to determine if a microorganism can ferment particular sugars.
(The fermentation tubes contain the sugar of interest [GLYCEROL, LACTOSE, MANNITOL],pH indicator [phenol red], and a Durham tube)
If a microorganism can ferment the particular sugar, then it will produce an acid in doing so. This acid will then lower the ph of the solution causing the liquid in the tube to turn yellow. Some M.Organisms also produce gas during fermentation.
(gas is important when identifying unknown bacteria)
gas appears as a bubble in the Durham tube.
An alkaline reaction can also occur.
(seen by the darkening of the red pH indicator color due to the utilization of peptone [a protein] in the broth.)

Yellow = ACID
Yellow+gas = ACID, GAS
Red to DARK RED = Negative or Alkaline

question

(MR) Methyl Red

answer

HCOOH --> CO2 + H2
Tests for a MIXED ACID FERMENTER
MIXED ACID FERMENTERS produce drastic amounts of acid from the fermentation of sugars. This acid results in lowering the pH BELOW 5.1 so that when the indicator methyl red is added the culture remains red.
(E. coli = MR +)

question

(VP) Voges-Proskauer

answer

HCOOH --> (AMC) Acetyl Methyl Carbinol --> 2,3 butanediol.
Tests for 2,3 butanediol fermentor.
2,3 butanediol fermentors produce less acid and more neutral products than mixed acid fermentors.
BECAUSE acetyl Methyl Carbinol (acetoin) is easier to detect than 2,3 butanediol fermentors ACETOIN is tested for when determining if a microorganism is a 2,3 butanediol producer.
VP1(alpha-naphthol) and VP2 (KOH) [Barrit's reagents] are added to the test tubes. When oxygen is present the KOH reacts with the ACETOIN to produce a BRICK RED COLOR which indicates the micro organism IS a butanediol2,3 producer.
(alpha-naphthol is used to intensify the red color.)
Enterobacter aerogenes = VP +

question

Catalase

answer

2H2O2 --> 2H2O + O2
(Catalase is an enzyme that converts hydrogen peroxide to water and oxygen)
Hydrogen Peroxide is produced during oxygen utilization and must be eliminated since hydrogen peroxide is toxic.
Catalase can be tested for by adding H2O2 to the culture and look for the production of oxygen bubbles.
(bubbles = + reaction)
(Lactobacillus lactus [Ll] is the only - that we studied)

question

Oxidase

answer

an enzyme which can oxidize aromatic amines to form colored products.
The aromatic amine used to test for oxidase is DIMETHYL-P-PHENYLENEDIAMINE HYDROCHLORIDE which turns a dark blue/black color when oxidase is present.
(+ for oxidase = turns a dark blue/black color)

question

Nitrate

answer

(NO3-) + 2e + (2H+) --> NO2 + H2O
NO3 --> NO2 --> N2 + NH3 + other products
Tests for the ability of microorganisms to REDUCE nitrate.
Nitrate broth contains (NO3-). Nitrate 1 (Sulfanilic Acid) and Nitrate 2 (Dimethyl-alpha-naphthylamine) reagents are added to broth. IF (NO2-) a product of nitrate reduction the broth appears RED. If the broth is red at this point it is NITRATE +.If no red color is seen at this point then we add zinc. (zinc is a catalyst that will convert NO3 --> NO2)
If the solution DOES NOT TURN RED it is said to be nitrate + at this point.(After adding Nitrate 1 & 2 "Red Color is seen = Nitrate +)(After adding ZINC "No Red Color" = Nitrate +)this is because when the NIT.1 & 2 are added it is testing for presence of NO2-, however NO2- could have been broken down into ammonia or other products. so we then test for nitrate to see if there is any left. If nitrate has been broken down (none is left) then the reaction is positive and we will not see the dark red color.

question

what are the 3 genre of spore forming bacteria

answer

Bacillus
(Aerobic, GRAM +, ROD)
Clostridium
(Anaerobic, GRAM +, ROD)
Sporsarcinae
(Cocci)

question

Tryptophan
(indole)

answer

Tryptophan --> Pyruvic Acid and Indole
Tests for the enzyme tryptophanase which converts tryptophan to indole and pyruvic acid.
Indole is tested for by adding Kovacs Reagent
(DIMETHYLAMINOBENZALDEHYDE, AMYL or BUTYL ALCOHOL, and HCl) which appears red in the presence of Indole.
(+ test = red color)

question

Urea

answer

Urea --> 2NH3 + CO2
tests for enzyme Urease which converts Urea to ammonia and CO2.
(Urea broth contains the substrate urea and pH indicator Phenol Red)
When ammonia is released the pH increases and when its above 8.1 the phenol red will appear red.
(+ test for Urease = Red color remains red!)
Proteus = Urease +

question

Hydrogen Sulfide Production

answer

Cystein -->H2S+ Amino Acrylic Acid (AAA) --> Imino Acid --> Pyruvic Acid + NH3
Tests for the enzyme cystein desulfurase which removes sulfur side chain from cystein to produce H2S. When IRON SALS are resent the H2S forms a black precipitate.
(Black precipitate = + test)
Proteus = H2S +

question

SIM

answer

Tests for sulfur (production of H2S), Indole, and motility.
H2S + = Black Precipitate
Indole + = Kovacs reagent turns red after addition
Motile + = growth away from inoculation line. (cloudiness in tube)

question

Simmons Citrate

answer

Tests for ability of M.Organisms to utilize citrate as the SOLE CARBON SOURCE.
If a microorganism can use citrate as the sole carbon source then it will grow on the bacterial medium and the media will turn a deep prussian blue color.
Gorwth on medium AND/OR the appearance of the blue color are both indications of a citrate + Microorganism.

question

(PPA) Phenylalanine

answer

Phenylalanine --> Phenylpyruvic Acid (PPA) + NH3
Tests for the presence of the enzyme phenylalanase which converts phenylalanine to PPA + NH3.
To test for the presence of PPA ferric chloride is added to media.
Ferric chloride will appear deep green if there is phenylalanase present.
+ PPA = deep green color

question

Litmus Milk

answer

Tests for lactose fermentation, reduction of litmus, presence of caseinase, and the deamination of amino acids to produce NH3.Litmus milk=pH indicator Litmus&powdered milk.
Acid reaction = pink liquid due to drop in pH from fermentation of lactose.Acid Curd reaction = pink solid due to acid production an coagulation of proteins causing the solid formation.Reduction = Litmus is reduced and is caused to be colorless and the tube appears white because ONLY MILK REMAINS.Alkaline Reaction = blue liquid which is usually cased when protein breakdown produces amino acids that are deaminated and release ammonia.Peptonization/Proteolysis = Clearing of medium (may be brown or amber) caused by the enzyme caseinase which breaks down the white protein casein in milk.MORE REACTIONS COULD OCCUR COMBINING THESE REACTIONS.

question

IMViC

answer

set of four tests that are used to differentiate between E.coli and Enterobacter a.
stands for :Indole, Methyl Red, Voges-Proskauer, and Citrate.
Ecoli is positive for Indole/Methyl Red tests
Enterobacter is positive for Voges-Proskauer/Citrate

question

Total Mag of microscope =

answer

Mag of Objective X Mag of Ocular

question

As you CLOSE the Iris Diaphragm what happens?

answer

1. Light intensity decreases
2. Contrast improves
3. Depth of field increases
4. Limits resolution (With oil immersion)

Spring ’11 Microbiology lab midterm (UCF) – Flashcards

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