lab study guide 3

selective medium for fungi, inhibits most bacteria with low pH.Used to grow mold and yeasts and inhibits the growth of bacteria

allows only one type of organism to grow, selective of one characteristic

Lactobacillus acidophilus

Rogosa SL

Lactic acid

The higher the incidence of lactobacilli in the mouth, the higher the incidence of dental caries (cavities).

Colonies on plate x dilution factor = bacteria/ml in saliva

Tryptocase soy agar with sheep blood added, about 5%. The nutrient in the medium is enriched by the blood which is required by the more fastidious organisms. Blood also serves as the indicator of hemolysis.

Selective and differential medium for the growth of staphylococci. The high salt concentration of this medium inhibits the growth of most bacteria, while staphlococcus grows uninhibited. As mannitol is fermented, the pH of the medium drops and the pH indicator in the medium turns yellow.

Media allows one to distinguish specific characteristics of different organisms.

To cultivate again on a new medium

Used as a simple test for lactobacilli. A change in color (yellow) indicates acid (lactic acid)

Uses glacial acetic acid and other agents to inhibit the growth of other oral flora, but does not affect the growth of lactobacilli.

Trypticase soy agar/general purpose agar. Is not specific for the growth of cocci, but does serve as an enrichment culture

Isolates Gram-positive bacteria (particularly cocci). Gram-negative will not grow on this medium.

- Selective medium for Gram-negative bacteria (particularly rods). Negative rods that do not ferment lactose will appear clear or milky. Lactose fermenters will appear dark and large. Some lactose fermenters will have a green metallic sheen.

Used to identify enteric (intestinal) cocci. The enteric cocci turn the agar black, which signifies the hydrolyzing of esculin. Other organisms will grow, but will not change the color of the medium.

- Slant tube medium. Contains three sugars: glucose, lactose, and sucrose. Only used for Gram-negative organisms. The butt will turn yellow if glucose is fermented and the slant will remain red. If two sugars are fermented, the entire tube will turn yellow. Aerogenic bacteris will produce gas and push the agar away from the bottom of the tube. If protein fermentation is present, the butt will turn black. If none of the sugars are fermented, the butt will not change color and the slant will turn red. This red slant indicates the fermentation of glucose and lactose or glucose and sucrose.

Slant tube medium. Used to differentiate between bacteria that uses citrate and those that do not. A blue slant indicates the utilization of citrate. Only used for aerogenic organisms that ferment both glucose and lactose.

Differential/slant tube medium. Used for Gram-negative bacteria. If it decomposes urea, the agar will turn a very vivid pink. If not, it will remain its original pale orange color.

Method for characterizing unknown species using the given choices and various test results.

a regular slip-cap culture tube with a small serological tube inverted inside to capture any gas bubble generated during fermentation. Media containing different sugars are used to determine the ability of organisms to ferment those sugars.

The EMB agar should have had small to medium sized, green metallic colonies, which is indicative of Escherichia coli in the water. Other types and colors of colonies may have been present. The Endo agar should have had a diverse array of colonies

Total Bacteria Count (TBC), Coliform Count, Somatic Cell Count

20,000/ml pasteurized grade A milk, 30,000/ml raw milk.

Proprionibacteria freudenreichii - gas produced on LB in Dunham tube, catalase positive.
Lactobacillus lactis - growth on Rogosa SL medium, negative catalase.
Streptococcus thermophilus - growth at 45C on blood agar; alpha-hemolytic, or growth on PEA at 45C, negative catalase test.

microbes that are deeply entrenched in the skin, difficult, if not impossible, to remove, and likely part of the normal microflora.

microbes found on the outer layers of the skin that are relatively easy to remove.

a growth medium that supports the growth of most aerobic and facultatively anaerobic bacteria

a panel of biochemical tests mostly used to distinguish between Escherichia coli and Enterobacter aerogenes

the conversion of ammonia to ammonium.

the removal of an amine group from a molecule; the enzymes that catalyse this reaction are called deaminases

a process in which nitrogen (N2) in the atmosphere is converted into ammonium (NH4+) or nitrogen dioxide (NO2).

a microbially facilitated process of nitrate reduction (performed by a large group of heterotrophic facultative anaerobic bacteria) that may ultimately produce molecular nitrogen (N2) through a series of intermediate gaseous nitrogen oxide products.

is a chemoautotrophic bacteria that oxidizes ammonia into nitrite as a metabolic process

plays an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil.

a soil bacteria that fix nitrogen when in an endosymbiotic association with roots of legumes

free-living, aerobic, capsule-forming, Gram-negative, nitrogen-fixing bacteria that may produce large quantities of capsular slime.

free-living, anaerobic, endospores-forming, Gram-positive bacilli that can fix nitrogen