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Totora Microbiology Lab Final Worksheet


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What is the purpose and selective agent in m-Staphylococcus Broth
10% NaCL This broth is an example of a selective medium: only certain types of organisms (those that can tolerate high salt levels) can grow in it.
What are the components of Mannitol Salt Agar?
contains mannitol, 7.5% sodium chloride and phenol red
What are the components of Staphylococcus medium 110 (SM110)?
contains mannitol, 7.5% sodium chloride and does not contain phenol red
What is the advantage of Mannitol Salt Agar?
The phenol red indicator will indicate mannitol fermentation
What is the advantage of SM110?
Without the phenol red you can see colony pigmentation by different strains of S aureus
What toxin is responsible for Beta Hemolysis?
Alpha toxin
What is the basis and procedure for coagulase test, what does a (+) reaction look like
it is a definitive test for Staphylococci aureus, inoculate a small tube of plasma and incubate at 37 water bath for several hours if plasma coagulate the organism is coagulase positive. any degree of coagulation is positive up to 24 hours
What are the three types of hemolysin patterns on Blood Agar plates?
Gamma (no change), Alpha (Greenish to brown halo around the colony), Beta (a zone of clearing around the colony, complete breakdown of hemoglobin; associated with pathogenic streptococci)
What is the typical appearance of S. aureus on MSA and BA Plates
MSA-yellow for fermentation of mannitol and BA zones of clearing indicating alpha toxin
Which Biochemical test is used to differentiate between Strep and Staph?
Catalase Strep are (-)no bubbles and Staph are (+) vigious bubbling
What is the criteria for Brown's classification of the Streptococci?
Beta Hemolysis-zone of clearing
How is Lancefield used to differentiate Beta Hemolytic Streptococci?
Based on antigenic (immunologic) make up of the organism
Which Lancefield group is clinically significant?
Group A- beta hemolytic streptococci that are sensitive to the antibiotic bacitracin clinically significant (pathogenic)
Lancefield groups are designated by the letters A through O
A serologic classification of bacteria of hemolytic streptococci into groups based on their specific carbohydrate antigen. Groups A through O have been established. All strains pathogenic to man belong in group A.
What were the 3 selective and differential media we used for isolation of gram negative intestinal pathogens?
MacConkey Agar, Hektoen enteric (HE), and Xylose Lysine Desoxycholate (XLD) agar
What is contained in the selective and differential media we used for isolation of gram negative intestinal pathogens?
may contain bile salts, and/or sodium desoxycholate to inhibit gran-positive bacteria. To inhibit coliforms and other nonenterics, they may contain citrate. All of them contain lactose and a dye so that if an organism is a lactose fermenter, its colony will take on a color characteristic of the dye present
What are the components of Kligler's Iron Agar (KIA)?
phenol red (pH indicator), glucose (1 X concentration), lactose (10 X concentration), iron salts
What are the 3 reaction patterns of Kligler's Iron Agar (KIA)?
red/red or K/K - no acid, neither glucose nor lactose fermented

red/yellow or K/A - acid from glucose only; lactose not fermented

yellow/yellow or A/A - acid from both glucose and lactose
What is alkaline reversion?
a condition in which the medium turns yellow during the first part of the incubation period and then changes to red later due to increased alkalinity.
What is the role of CaCl2 in Bacterial Transformation?
to help lower negative charge of cell to allow (-) DNA to pass
What is special about the MM294 strain of E. coli used in Bacterial Transformation?
What is the source of DNA for Bacterial Transformation?
.005 ug/ul of pAMP
What is the purpose of the heat shock step in Bacterial Transformation?
Causes pores to expand in cells so DNA can get in
What enzyme provides resistance to ampicillin in Bacterial transformation?
What is the mode of action of B-lactanase?
catalyze the hydrolysis of B-lactam antibiotics
What is illustrated by each of the 3 control plates in bacterial transformation
-pAMP on LB-orginal culture was viable (+) control; -pAMP on LB/AMP-orginal culture was sensitive to aampicillin (did not have b-lactamase) (-) control; +pAMP on LB-transformation protocol did not kill cells (+) control
What is the purpose of adding lysozyme, SDS and Phenol/Chloroform during DNA isolation procedure?
lysozme-breaks down cell wall; SDS detergent to break down cell membrane; Phenol/Chloroform removes proteins from mixture
How do restriction endonucleases work?
Nuclear scissors, make double stranded cuts-staggered, made by bacteria, cut foreign DNA at specific "recognition sites"
What is the basis of electrophoresis
Separation based on charge, size and shape, -DNA will be forced to move to postive charge
What chemical is used to visualize DNA?
ethidium bromide
What are the advantages and disadvantages of using API20E system compared to convential tests?
advantages easy to inoculate and easy to read; disadvantages may be forced into a number that does not quite fit.

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