1. The Effects of Antibiotics on Yeast Survivorship
Chawrley Curr
Grade 10
Pittsburgh Central Catholic High School

2. Candidiasis Commonly known as yeast infections
Caused by uncontrolled multiplication of yeast cell Candida albicans in body
Candida albicans can live in human mouths and in the gastrointestinal tract without causing harm
Antibiotics and steroids use are most common reason for yeast infections
Oral Yeast Infection

3. Nystatin Antifungal drug
Used for treatment of yeast infections of the stomach, mouth, intestine and mucus membranes
Attaches to ergosterol which is a major component of cell membrane
Ergosterol is unique to fungi so nystatin does not have a catastrophic impact on animals

4. Saccharomyces cerevisiae
Eukaryotic
Reproduces by budding
Most commonly studied eukaryotic model organism
Top-fermented yeast

5. Ampicillin Penicillin antibiotic
Used in treatment of bacterial and fungal infections
Acts as competitive inhibitor of an enzyme and inhibits the final stage of cell wall synthesis and causes cell lysis

6. Materials: 60 YEPD agar plates ( Klett spectrophotometer
Sterile pipette tubes
Micropipettes
4 one liter beakers
Vortex
Incubator
Sidearm flask
Spreading platform
Spreader bar
Ethanol
20 mL Sterile capped test tubes with sterile dilution fluid (SDF)
Ampicillin
Nystatin Suspension

7. Procedure: Yeast was grown overnight in sterile YEPD agar media
A sample of the overnight culture was added to fresh media in a sterile sidearm flask.
The culture was placed in a shaking water bath (30°C) until a density of 50 Klett spectrophotometer units was reached. This represents a cell density of approximately 107 cells/ml
The culture was diluted in sterile dilution fluid to a concentration of approximately 107 cells/ml
The selected experimental variables were diluted with sterile dilution fluid to the chosen concentrations to a total of 9.9mL
0.1 mL of cell culture was then added to the test tubes, yielding a final volume of 10 mL. and a cell density of approximately 103 cells/mL
The solution was mixed by vortexing and allowed to sit at room temperature for 15 minutes
After vortexing to evenly suspend cells, 0.1 mL aliquots were removed from the tubes and spread on 60 plates
The plates were incubated at 30°C for 12 hours.
The resulting colonies were counted. Each colony is assumed to have arisen from one cell.

8. Purpose: Hypothesis: Null Hypothesis:
To determine how various concentrations of antibiotics and antifungals affect yeast survivorship
Hypothesis:
Increasing concentrations of antibiotics and antifungals will result in the decrease of yeast survivorship
Null Hypothesis:
There will be no significant variation in yeast survivorship at all concentrations