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Review Pt. 1
Review Pt. 1
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Microbiology: A Human Perspective
Microbiology: A Human Perspective w/ARIS bind in card
A spectrophotometer is used to measure cell turbidity by measuring the absorbance or optical density of a culture t/f
Bacteria adap to the new environment in this phase
At least 10% broth displacement in the durham tube is considered a negative for gas production in the MPN presumptive test t/f
The pore size of the membrane filter used for microbial testing of water is ___
A microscope with an objective lens magnification of 10x will have a total magnification of
Gram-positive lose the purple crystal violet on washing with 3% alcohol
The primary stain in the endospore stain is
An example of coliform is
The mEndo broth MF plates inhibit the growth of gram-positive organisms t/f
Fomites are inanimate objects that can harbor microorganisms t/f
4 common colony shapes
punctiform, round, filamentous, irregular
5 common colony margins
smooth, curled, wavy, lobate, filamentous
4 common colony surface characteristics
smooth, concentric, wrinkled, contoured
species tested in bacterial motility - tube method
E. coli (motile) and K. pneumoniae (non-motile)
species tested in bacterial motility - plate method (swarming)
P. mirabilis (swarms) and E. coli (doesn't swarm)
example for flagella stain
Proteus vulgaris (shows peritrichous arrangement)
steps of Gram stain
1. crystal violet - primary stain
2. iodine - mordant
3. alcohol - decolorizer
4. safranin - counter stain
S. aureus morphology
E. coli morphology
B. megabacterium morphology
gram + rods
M. catarrhalis morphology
Acid-fast stain used to identify....
--have mycolic acid
Kinyoun acid-fast stain
doesn't use heat but requires long exposure to carbolfuschin
Ziehl-neelsen acid-fast stain
requires application of heat for the dye to penetrate the cell wall
Acid-fast stain steps
1. carbolfuschin - primary stain
2. 3% acid alcohol - decolorizer
3. methylene blue - counterstain
Mycobacterium smegmatis acid fast?
Staphylococcuss aureus acid-fast?
2 genera with endospore stage
Bacillus and Clostridium spp.
Schaeffer-Fulton quick spore stain steps
1. flame 10 times
2. malachite green - stains spores
3. safranin - stains vegetative cells
usual concentration of agar
examples of differential and selective media (Lab 4)
Mannitol Salt Agar (MSA) differentiates Staph sp. based on ability to ferment mannitol pink-->yellow
Eosin Methylene Blue Agar (EMB) differentiates G- rods based on fermentation of lactose: E. coli colonies w/ green metallic sheen, other G- dark
Complex medium, defined medium
15 psi at 121C for 15-20 min
Most Probable Number test steps
define Indicator organisms
associated with the intestinal tract
indicator that meets 4 criteria:
ferments lactose to acid and gas in 48 hrs at 37C
why is E. coli a good indicator for fecal contamination?
lives in intestines
not usually in soil or water
not as fastidious as others
MPN presumptive test steps
15 tubes: 5 of dbl strength LST or lactose broth, 10 mL
5 of 1x strength, 1 mL
5 of 1x strength, 0.1 mL
define membrane filter method
water filtered through a membrane with pore size 0.45 um
utilizes m Endo broth MF or EMP agar
ideal sample yields 20-80 coliform colonies
There must be a _____ displacement in Durham tube to be considered positive for gas production
define confirmed test
ensures G-neg rods!
inoculate EMB w/ gas positive tube
How many CFUs make a countable plate?
bacterial growth phases
With a spectrophotometer, the higher the absorbance...
the greater the concentration of bacterial cells
inoculate TSA plate and LST/lactose broth tube from growth on EMB plate.
Streak for isolation
how to calculate #CFU/mL or /g of food
#CFU counted on plate x reciprocal of dilution
-5 to 20C
20 to 50C
50 to 80C
capable of growth at temp higher or lower than their optimum
eg Pseudomonas fluorescens
Neutrophile, Acidophile, Alkaliphiles
Hypertonic, Hypotonic, Isotonic
defined in terms of the solution
require high concentrations of salt to grow
eg Halobacterim salinarium (25% salt)
capable of growth in moderate concentrations of salt
eg. S. aureus 10% salt
ex of obligate aerobe Lab 7
ex of obligate anaerobe Lab 7
ex of facultative anaerobe Lab 7
ex of microaerophile Lab 7
ex of aerotolerant organism Lab 7
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