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.
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
a culture of a microorganism maintained solely for the purpose of keeping the organism in a viable condition by subculture into fresh medium
allows the growth of certain kinds of bacteria while inhibiting the growth of others
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
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
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
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.
Mixes with reagants A & B after 4 days. After adding the reagants look closely for color change which indicates acetoin production.
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.