Microbiological Theory &
Applications Laboratory
Manual MID-EXAM 2024/2025
Mannitol Salt poor growth - ANSWER>>>organism inhibited by NaCl, not staph
mannitol salt good growth - ANSWER>>>organism not inhibited by NaCl, staph
Macconkey poor growth - ANSWER>>>organism is inhibited by crystal violet and or bile, gram +
macconkey good growth - ANSWER>>>organism is not inhibited by crystal violet or bile, gram +
EMB poor growth - ANSWER>>>organism is inhibited by eosin and methylene blue, gram +
EMB good growth - ANSWER>>>organism is not inhibited by eosin and methylene blue, gram -
Phenol red broth yellow with bubble - ANSWER>>>fermentation with acid and gas end products, A/G
filiform - ANSWER>>>dark and opaque with smooth edge
simple stain - ANSWER>>>crystal violet, safranin, methylene blue
negative stain - ANSWER>>>determines morphology and cellular arrangement without heat fixing
(background is stained)
do you heat fix capsules - ANSWER>>>no
what color are endospores - ANSWER>>>green
gram - vs gram + - ANSWER>>>- ends red,
+ ends purple
gram stain based on cell wall - ANSWER>>>gram negative have higher lipid content and thinner
peptidoglycan layer. gram negative harder to retain crystal violet. the thick peptidoglycan layer traps the
crystal violet complex and makes it less susceptible to decolorization for gram +
gram + organisms - ANSWER>>>bacillus and staph lose their ability to retain the crystal violet iodine
complex in as little as 24 hours of incubation
acid fast stain used for - ANSWER>>>differential stain to detect cells capable of retaining a primary stain
when treated with an acid alcohol
capsule stain - ANSWER>>>stain around cell because capsules are composed of mucoid polysaccharides
that repel most stains, can increase virulence
, 3 words to describe colony shape - ANSWER>>>round, irregular, punctiform
punctiform - ANSWER>>>pinpoint, tiny; used to describe colony shape
Entire - ANSWER>>>word to describe a colony margin that is smooth with no irregularities
Undulate - ANSWER>>>word to describe a colony margin that is wavy
Lobate - ANSWER>>>word to describe a colony margin that is lobed
filamentous - ANSWER>>>word for a colony margin that appears to have filaments
rhizoid - ANSWER>>>word for a colony margin that is branched like roots
6 words that describe colony texture - ANSWER>>>moist, mucoid, dull, butyrous, dry, shiny
Polvinate - ANSWER>>>word for colony elevation that means very convex
umbonate - ANSWER>>>word for colony elevation that means raised center
words to describe colony elevation - ANSWER>>>flat, raised, convex, pulvinate, umbonate
words to describe colony surface - ANSWER>>>smooth, rough, wrinkled
trichomes - ANSWER>>>chains of cyanobacteria, visible without staining and with dry magnification.
they have a
Description of bacteria in microspopic viewing - ANSWER>>>transparent cells in shapes of rods (bacilli),
spheres (cocci), spirals (spirilla). Sometimes found in chains like cyanobacteria.
Description of chlorophytes (archaeplastida) - ANSWER>>>Distinctive by green chloroplasts, thick cell
walls, vacuoles and nuclei. May be seen as single cells, colonies, or branched or unbranched filaments.
Description of SAR supergroup - ANSWER>>>Golden brown in color, Can be round, or symmetrical and
elongated. Have two overlapping halves called a frustule.Includes ciliates.
Amoeba (unikonta) - ANSWER>>>blobby with flowing cytoplasm and constantly changing shape, visible
nucleus
cocci - ANSWER>>>spheres
bacilli - ANSWER>>>rods
spirilla - ANSWER>>>spirals
vibrios - ANSWER>>>slightly curved rods
coccibacilli - ANSWER>>>short rods
spirochetes - ANSWER>>>flexible spirals
simple stain - ANSWER>>>used to make cell morphology, size and arrangement more visible. Basic stains
are attracted to the negative charges on the surface of most bacterial cells
Chromagen - ANSWER>>>a colored molecule dissolved in a solven, used in staining
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