LAB 8 Flashcards
Zone of inhibition
the area around the disk in which no bacteria grows and determines the susceptibility rating of bacterium to a specific antibiotic
Sensitive
if a bacterium is susceptible to the effect if an antibiotic (kills or inhibits growth)
Resistant
not susceptible to an antibiotic
Intermediate
Some bacteria may be gaining resistance to the antibiotic
*Another concentrations or multiple antibiotics are needed
Another form of horizontal gene transfer, Cells pick up free DNA from the environment
Transformation
Cells will secrete exoenzymes into the environment and digest large molecules, like DNA, into its base components and then bring it into the cell
Endocytosis
Cells that expressed a protein system on their surface which allows them to move intact ssDNA into the cells
Competent
What is the process of transformation
- Competent cells express DNA binding protein
- Once bound, a nuclease domain on the complex will digest one of the strands of DNA bound to the complex
- The undigested ssDNA will then be transported into the cell intact
- Once in the cell, it undergoes homologous recombination, delivering novel traits into the host cell
- If its a plasmid, DNA can circularize and synthesize its complementary strand and exist extra chromosomally
The family are gram-negative rods that ferment glucose
Can be normal gastrointestinal microbiota, opportunists, and pathogens
Salmonella, E coli
Enterobacteriaceae
Allows us to determine their presence of enzymatic activity because some enzymes cause changes in the pH of the media
Differential media
Combined media that tests for motility, sulfur reduction to hydrogen sulfide, indole production from amino acid tryptophan
SIM MEDIA
the enzyme that hydrolyzes the amino acid tryptophan to produce indole and pyruvate
trytophanase
Glucose, sucrose, lactose
Triple sugars
tests for the ability to use citric acid utilization
Media contains sodium citrate as the sole carbon source
Simmons citrate agar
Differentiates bacteria based on sugar fermentation and sulfur reduction
Differentiates bacteria on fermentation of glucose, sucrose, and lactose or not
How to tell is positive?
Triple sugar iron (TSI) agar
Positive - yellow
If the entire tube is yellow - bacteria fermented the glucose and at least 1 other
GAS - observed by breaks in the agar
