Exam 3 Flashcards
dormant cells when conditions (temp and nutrient depletion) are unsuitable
endospores
what are endospores highly resistant to
heat and chemicals
what is endospore resistance due to
keratin (outer covering resists staining), dehydrated state, DNA protective proteins
what do endospores have total absence of
ATP
these are metabolically active
endospores turn into this when conditions are suitable
vegetative cells
method of staining endospores
Schaeffer-Fulton
what is the primary stain of Schaeffer Fulton procedure
malachite green(forced into spore by steaming)
this is water soluble and has a low affinity for cellular material
malachite green
these are responsible for producing the endospore
spore mother cells
what are the three possible locations of endospores
central, terminal and subterminal
what are the two possible shapes of endospores
spherical and elliptical
what is the endospore stain used for
to detect presence, shape and location of endospores in bacterial cells
what are two common genra that carry endospores
Bacillus and Clostridum
what are the general steps of endospore staining
1)heat fix 2)steam with malachite green 3)rinse with DI water 3) counterstain with safrainin
what is the oxidase test designed to identify
the presence of cytochrome c oxidase
what converts enzymes back to their oxidized state
electron transport chain
what are the two mechanisms of ETC
1) transport electrons down chain to terminal electron acceptor
2) generate proton motive force by pumping H
what are unable to donate protons in ETC
flavoproteins, iron sulfur proteins, and cytochromes
tetramethyl p phenylenediamine
chemicals that develop color as oxidize
cheromogenic reducing agent
what does a dark blue/purple result after 20 sec of oxidase test mean
positive result, cytochrome c oxidase is present
what does no color change after 20 sec of oxidase test mean
negative result, cytochrome c oxidase is not present
these are natural antimicrobial agents produced by microbes
antibiotics
tool for establishing the effectiveness of antimicrobics against pathogenic microbes in clinical labs
Kirby-Bauer
what occurs as the drug moves through the agar in Kirby Bauer
concentration gradient is formed
forms if organism is susceptible to drug
area around disk where concentration is high enough to strop growth
zone of inhibition
junction where concentration of antimicrobic has become too low to stop growth
minimum inhibitory concentration (MIC)
does a clear zone mean the bacteria has been killed
no
drugs that kill the organism
bactericidal
drugs that stop bacteria from dividing (does NOT kill)
baceriostatic
zone diameter below which all resistant strains fall
resistance breakpoint
zone of diameter above which all susceptible strains fall
susceptibility breakpoint
what is the disk diffusion test a method to measure
the effectiveness of antibiotics and other chemotherapeutic agents on pathogenic microbes
what is MacConkey agar selective for
gram negative organisms
what do the indicators of MacConkey do
differentiate lactose fermenters from lactose non fermenters
what does MacConkey agar contain
bile salts, lactose, neutral red, and crystal violet
what do the bile salts and crystal violet of MacConkey do
inhibit growth of gram positive organisms
when is neutral red dye, red and colorless
colorless above pH 6.8 and red below
what is MacConkey agar used for
to differentiate members of Enterobacteriaceae based on the ability to ferment lactose
what does poor or no growth on MacConkey agar mean
inhibited by CV and or bile salts so gram positive
what does good growth on MacConkey agar mean
not inhibited by CV and or bile salts so gram negative
what does pink/red growth on MacConkey agar mean
produces acid from lactose fermentation so coliform
what does colorless growth on MacConkey agar mean
does NOT ferment lactose so noncoliform
what is the oxidation fermentation test designed for
to differentiate bacteria on the basis of fermentation or oxidative metabolism of carbohydrates
oxidative organisms oxidize
carbohydrate to CO2, H2O and energy
what is the process of oxidation and fermentation
glycolysis-oxidation of pyruvate-citric acid cycle-ETC
what is the significance of high sugar to peptone ratio in oxidation fermentation test
to reduce possibility that alkaline products from peptone utilization will neutralize weak acids
what are the pH results of bromothymol blue dye
yellow(6), green (7.1), blue (7.6)
what is the oxidation fermentation test medium composed of
glucose, lactose, sucrose, maltose, mannitol, or xylose
what is the significance of sealing a tube with sterile mineral oil
promote anaerobic growth and fermentation
creates environment unsuitable for oxidation
why is a tube left unsealed
to allow for aerobic growth and oxidation
sealed green or blue and unsealed yellow mean
oxidation
sealed yellow and unsealed yellow
oxidation and fermentation or just fermentation
slightly yellow at top both sealed and unsealed
oxidation and slow fermentation or just slow fermentation
green or blue both sealed and unsealed
no sugar metbaolism
semisolid medium designed to detect bacterial motility
motility test agar
what is the concentration of motility test agar
0.4% to maintain form but allow movement of motile bacteria
this is added to make interpretation of motility test easier
tetrazolium salt (TTC)
what is used as an electron acceptor
TTC
in its oxidized form TTC is
colorless and soluble
in its reduced form TTC is
red and insoluble
what does a positive motility test look like
red radiating outward from central stab
what is an important differential characteristic of Enterobacteriaceae
motility
