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The Effects of Antibiotics on Yeast
Survivorship
Chawrley Curr
Grade 10
Pittsburgh Central Catholic High School
Candidiasis
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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
Nystatin
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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
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Ergosterol is unique to fungi so nystatin does not have
a catastrophic impact on animals
Saccharomyces cerevisiae
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Eukaryotic
Reproduces by budding
Most commonly studied
eukaryotic model
organism
Top-fermented yeast
Ampicillin
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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
Materials:
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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
Procedure:
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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.
Purpose:
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To determine how various concentrations of
antibiotics and antifungals affect yeast survivorship
Hypothesis:
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Increasing concentrations of antibiotics and
antifungals will result in the decrease of yeast
survivorship
Null Hypothesis:
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There will be no significant variation in yeast
survivorship at all concentrations