50 terms

Microbiology lab practical

microbial culture
One of the diagnostic methods of microbiology and it is used to determine the cause of an infectous disease by allowing the microorganism to multiply in certain specific media under controlled lab conditions.
contains nutrients for growth of microbes.
visible mass of microorganisms growing on a solid medium; in general it is formed from reproduction of a single cell so that all the members of a colony are desendant from that original cell
mixed culture
two or more kinds of microbial species are found
pure culture
one kind of microbial species is found
stock culture
a culture of a microorganism maintained solely for the purpose of keeping the organism in a viable condition by subculture into fresh medium
selective medium
allows the growth of certain kinds of bacteria while inhibiting the growth of others
differential medium
allows you to differentiate microbes based on thier metabolic activity
Types of differential Mediums
Blood Agar, gelatin, SIM Tubes, Simmons Citrate
Types of Selective Medium
Sabouraud Dextrose
Both Selective & Differential Medium
Kligler Iron Agar, Mac Conkey Agar, Mannitol Salt Agar
Neither Selective nor Differential
Mueller-Hinton Agar, Nutrient Agar
total Magnification
determined by multiplying the eye piece power (usually 10x) by the objective lens in place. EX. a 10x eyepiece and a 4x objective yields a total magnification of 40x
working distance
distance between the objective lens and the specimen. At low mag the working distance is longer
specimens that appear in focus or centered in the field of view at one magnification level will also appear centered when mag level is changed
cloudiness of broth
cottony or wooly masses floating in broth
"skin" that forms on the surface of a broth culture
primary stain
Stains what you want to see;crystal violet
sets dye; fixes crystal violet to cell wall;iodine
makes cells or structures more visible;safranin
Why is a dilution series often done before making colony counts?
By diluting it becomes easier to identify viabile colonies when using streak plate method.
Determining # of organisms in original culture
# if colonies x plating dilution factor x tube dilution factor
What is meant by "Zone of Inhibition"?
The area on an agar plate where growth of a control organism is prevented by an antibitic, usually placed on the agar surface. If the organism is suseptible to the abntibiotic there will not be growth where the anitibiotic is.
For what reasons might a chemical that is usually thought to be a good antimicrobial show no zone of inhibition?
• They have acquired antibiotic resistance
• The antibiotic disk isn't carefully pressed down enough into agar plate before being inverted and incubated
Why is it important for many of the media used this semester to set up a negative control tube?
For the comparison to see exactly what and how much growth.
How would you test for the ability of a microbe to produce catalase?
Use loop to transfer some growth from bacteria to a clean microscope slide. Use sterile dropper to apply several drops of hydrogen peroxide to bacteria. Bubbling indicates the release of oxygen gas and a positive reaction for the enzyme catalase
What medium is used to test for hemolysis?
Blood Agar
Hemolysis destroys red blood cells
What chemical is added to starch plates to test for reaction?
What is enzyme that breaks down starch?
Gram positive
Gram Negative
Basic Shape of bacteria
coocus, rod(bacillus), and spiral
Basic Shape of Endospore
Basic Shape of Algea on wet mount
Basic Shape of Aspergillus
Basic Shape of Penicillium
skeleton fingers
Basic Shape of Rhizopus
Tootsie Pop
Basic Shape of Plasmosium
circle, crescent, sausage shaped
Basic Shape of Trypanosoma
Basic Shape of Balantidium
Oval (kind of flask shaped)
Process used to grow lytic phages
Pour mixture of bacterial stock, viral dilution, and soft agar over agar plate. These mixtures solidify and are then incubated.
Voges-Proskauer Test
Mixes with reagants A & B after 4 days. After adding the reagants look closely for color change which indicates acetoin production.
Heat fix
Pass slide through flame 3 times.
obligate aerobes
Must have oxygen in order to breakdown organic molecules for energy
Microbes that can produce energy through both anaerobic and aerobic . Organisms remove electrons from organic fuels and pass these electrons to other organic compounds. Final product often includes some type of acid and gas.
Faculative anaerobes
Can survive with or without oxygen
Obligate anaerobes
Can only produce energy anaerobically and oxygen is toxic
What do you use to test for motility?
SIM tube (Sulfide, Indole, Motility)
hair like structures that allow bacterial cells to attach to each other.
What are Durham tubes used for?
To test for the ability of microbes to ferment a variety of different carbohydrates.