32 terms


Mannitol Salt Agar
Bacteria that tolerate 7.5% NaCl (Sodium Chloride) Aka (Salt) can be grown on MSA. Acid from fermentation of mannitol will turn the phenol red indicator yellow. (selective media)

(Special Media for Isolating Bacteria)
How do the results observed on the Mannitol Salt and EMB correlate to the Gram reaction of the bacteria?
Gram (-) only grows on the EMB Agar and Gram (+) grows only on the Mannitol Salt Agar.
How can you Identify the growth?
By comparing plates of unknown organism to the known organisms.
What is the purpose of peptone in the media?
The peptone is used as a nutrient souce of Carbon, Nitrogen, and Energy for growth
What is the purpose of Agar in the media?
Agar is used to solidify the bacteria in the media
Growth on EMB media
E. coli (green metallic) and P.aeruginosa (colorless)
Growth on MSA agar
S. aureus (yellow colonies) and M. letues (white colonies)
enrichment, selective, and differential media
Help isolate organisms found in the minority; either enhance the growth of some organisms or inhibit the growth of other organisms.
Selective Media (Mannitol Salt Agar)
Contains chemicals that prevent the growth of unwanted bacteria without inhibiting the growth of the desired organism.
Enrichment Media
Contains chemicals that enhance the growth of the desired bacteria. Other bacteria will grow, but the growth of the desired bacteria will be increased.
Differential Media(EMB media)
Contains various nutrients that allow the investigator to distinguish one bacterium from another by how they metabolize or change the media.
color change in the medium
Products of bacterial metabolism can react with the dyes (eosin and methylene blue) May inhibit the growth of some organisms.
What would be found in the clear area that would not be found in the blue area of a starch agar plate after the addition of iodine?
glucose & exoenzymes
What are exoenzymes?
mainly hydrolic enzymes that leave the cell and breakdown
What organism give a positive result for starch hydrolysis
Bacillus subtilis
What is amylase?
It hydrolyzes the polysacharide into smaller carbohydrates
How can you tell if an organism oxidizes glucose on an OF-glucosemedium?
The medium contains bromythmol blue,which turns yellow in the presence of acids,indicating catabolism of the carbohydrate.
How can you tell if an organism ferments glucose on an OF-glucosemedium?
If the carbohydrate is metabolized in both tubes fermentation has occurred
Organisms that do not use glucose oxidatetively or fermentatively can derive energy from where?
By oxidizing the peptone
What alkaline product is released from the breakdown of amino acids and can neutralize the acid?
What is catabolism?
Chemical reactions that release energy from the decomposition of complex organic molecules
What are carbohydrates?
organic molecules that contain carbon,hydrogen,and oxygen in the ration CH2O
What are exoenzymes?
mainly hydrolytic enzymes that leave the cell and breakdown ,by the addition of water,large substrates into smaller components,which can then be transported into the cell.
Fermentative catabolism does not require oxygen but may occur in its presence? True or False?
Most bacteria cannot ferment glucose without using oxygen? True or False?
What are the metabolic end-products of fermentation?
small organic molecules,usually organic acids
What is OF-Mediium?
a nutrient semisolid agar deep containing a high concentration of carbohydrate and a low concentration of peptone.
What will the peptone support on the OF-Medium?
the growth of nonoxidative ,nonfermentative bacteria.
Why are fermentation tubes evaluated at 24 & 48 hrs?
Fermintation occurs with or without oxygen present however during prolonged incubation periods many bacteria will begin growing oxidatively on the peptone
What would happen if an organism used up all the carbohydrate in the fermentation tube?
It would cause neutralization of the indicator turning it red
What would the organism use for energy?
How could you determine whether a bacterium fermented the following carbohydrates, mannitol,sorbitol,adonitol,or arbinose?
color change and form of gasses