Effects of Road Salt Deicers on Yeast Survivorship James Brunner Pittsburgh Central Catholic High School Grade 9

Introduction  In this experiment, a yeast culture was tested under the effects of various chloride salts  Model- yeast, Variable- chloride salts, Interaction- yeast survivorship  Idea arose from wondering what happens to ecosystems in winter with road salt

Yeast  Eukaryotic organism used in foods and drinks  Most commonly studied organism in labs  Easy to use- grows quickly, easy to count colonies, and nonpathogenic (safe to use)  Less tolerable to extreme conditions- achieves better data

Sodium Chloride  Standard salt used to de-ice roads  Known damages- harmful to water, plants, metals, and even the roads it’s used on  One of the cheapest salts to melt ice  Past studies- as salt content increased, yeast survivorship decreased  Chemical Symbol: NaCl

Magnesium Chloride  Also used as road salt de-icer  Less harmful then Sodium Chloride  Known to damage metal and concrete, but still known as best for metal and concrete  Contains 17-56% more chloride ion than other salts  Melts ice at slower rate than other chloride salts  Chemical Symbol: MgCl 2

Potassium Chloride  Another salt used as de-icer  Thought to be one of the “safer” salts to melt ice with  Used as sodium-free substance for table salt  Known as best for use with vegetation  Chemical Symbol: KCl

Purpose & Hypotheses  Purpose- to determine the effects of various chloride salts on a yeast culture  Null Hypothesis- The survivorship of the yeast cells will not be affected by any of the three chloride salts  Alternative Hypothesis- all three chloride salts will be more harmful to yeast then if the yeast cells were left alone; Sodium Chloride will be the most harmful and Potassium Chloride will be the least harmful

Methods and Materials Materials:  60 agar plates  Yeast Culture  NaCl  KCl  MgCl 2  Pipette  10 test tubes  Water  Ethanol  Ethanol Spreader  Burner  Weigh boat  Scale  Incubator  Vortex Genie  3 mixers

Methods and Materials (continued) 1..1%,.5%, and 1% concentrations of NaCl, KCl, and MgCl 2 were created in test tubes 2. 1 test tube without any salt for control 3. Yeast was added to test tubes 4. 1 ml from each test tube was pipetted onto 6 agar plates, resulting in a total of 60 plates 5. Colonies counted after 2 days

Data Analysis  The data was analyzed using ANOVA Charts  9 ANOVA charts were created-  1 for all data  1 for each concentration of salt with the control (no.5% KCl)  The Dunnett Test was used on all ANOVA charts for stronger data

ANOVA Chart

Results  All salts affected the yeast; yeast survivorship declined as salt concentration rose  NaCl was the least harmful, while MgCl 2 was the most harmful  All plates grew yeast well; except for the plates containing.5% KCl, which was contaminated and did not grow any yeast  The results in this experiment pertained to those of past studies of this nature

Effects of Salt on Yeast Survivorship #ofcolonies#ofcolonies Type of Salt Salt Concentration

Pictures NaCl 1%KCl.1%

Pictures (continued) MgCl 2.5%No Salt Added

Final Interpretations  After the data was collected, the alternative hypothesis was overall correct  All colonies affected negatively by the salts  Some of alternative hypothesis incorrect- Sodium chloride least instead of most harmful, MgCl 2 most harmful, KCl in middle  According to data, road salt de-icers inhibit the growth of yeast colonies

Final Interpretations (continued)  After ANOVA and Dunnett tests, null hypothesis rejected  Most ANOVA tests showed null hypothesis accepted (most p values over.05), but Dunnett test showed that it was rejected (most t values less than t critical)  Dunnett test more powerful than ANOVA- compares better over two groups of data  ANOVA tests may have shown that null was accepted as decreases in yeast survival not very large, but clearly exist

Limitations and Extensions Possible flaws of experiment:  Only complete set of data-NaCl  All 5% KCl contaminated-data could not be obtained; 1 plate in 5% MgCl 2 contaminated  After removal from incubator, lids from 3 plates broken when placed in stacks  May have caused colonies to be smudged around, resulting in incorrect data

Limitations and Extensions (continued) Extensions:  More concentrations and salts added  More plates used for each concentration of salt  Another model, such as bacteria, added to achieve better data

References  “Rock Salt (NaCl) Sodium Chloride.” Peterschemical.com Dec. 21, <  “Potassium Chloride and Urea.” Peterschemical.com Dec. 21, <  “Magnesium Chloride.” Peterschemical.com Dec 21, <  “Yeast.” Wikipedia.org Dec. 21, <  “Sodium Chloride.” Wikipedia.org Dec. 21, <  “Magnesium Chloride.” Wikipedia.org Dec. 21, 2007 <

References (continued)  “Potassium Chloride.” Wikipedia.org Dec. 21, 2007 <  “Road Salt and Water Quality.” Des.state.nh.us Dec. 21, 2007 <  “Field and laboratory investigations on the effects of road salt (NaCl) on stream macroinvertebrate communities.” Sciencedirect.com Dec. 21, 2007 < di=B6VB5- 455VM763&_user=10&_rdoc=1&_fmt=&_orig=search&_sort =d&view=c&_acct=C &_version=1&_urlVersion= 0&_userid=10&md5=c9d9b919f172d211bbad1839fd5d0afe  “Effect of Sodium Chloride on Bakers' Yeast Growing in Gelatin.” Aem.asm.org Dec. 21,