Effects of Road Salt Deicers on Yeast Survivorship

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

2. 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

3. 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 Yeast

4. 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 Sodium Chloride

5. 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: MgCl2 Magnesium Chloride

6. 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 Potassium Chloride

7. 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

8. Materials: 60 agar plates Yeast Culture NaCl KCl MgCl2 Pipette 10 test tubes Water Ethanol Ethanol Spreader Burner Weigh boat Scale Incubator Vortex Genie 3 mixers Methods and Materials

9. Methods and Materials (continued) • .1%, .5%, and 1% concentrations of NaCl, KCl, and MgCl2 were created in test tubes • 1 test tube without any salt for control • Yeast was added to test tubes • 1 ml from each test tube was pipetted onto 6 agar plates, resulting in a total of 60 plates • Colonies counted after 2 days

10. 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

11. ANOVA Chart

12. Results • All salts affected the yeast; yeast survivorship declined as salt concentration rose • NaCl was the least harmful, while MgCl2 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

13. Effects of Salt on Yeast Survivorship # o f colonies Salt Concentration Type of Salt

14. Pictures NaCl 1% KCl .1%

15. Pictures (continued) MgCl2 .5% No Salt Added

16. 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, MgCl2 most harmful, KCl in middle • According to data, road salt de-icers inhibit the growth of yeast colonies

17. 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

18. 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% MgCl2 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

19. 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

20. References • “Rock Salt (NaCl) Sodium Chloride.” Peterschemical.com Dec. 21, 2007. <http://www.peterschemical.com/sodium-chloride/ • “Potassium Chloride and Urea.” Peterschemical.com Dec. 21, 2007. <http://www.peterschemical.com/potassium-chloride/ • “Magnesium Chloride.” Peterschemical.com Dec 21, 2007. <http://www.peterschemical.com/magnesium-chloride/ • “Yeast.” Wikipedia.org Dec. 21, 2007. <http://en.wikipedia.org/wiki/Yeast • “Sodium Chloride.” Wikipedia.org Dec. 21, 2007. <http://en.wikipedia.org/wiki/Sodium_chloride • “Magnesium Chloride.” Wikipedia.org Dec. 21, 2007 <http://en.wikipedia.org/wiki/Magnesium_chloride

21. References (continued) • “Potassium Chloride.” Wikipedia.org Dec. 21, 2007 <http://en.wikipedia.org/wiki/Potassium_chloride • “Road Salt and Water Quality.” Des.state.nh.us Dec. 21, 2007 <http://www.des.state.nh.us/factsheets/wmb/wmb-4.htm • “Field and laboratory investigations on the effects of road salt (NaCl) on stream macroinvertebrate communities.” Sciencedirect.com Dec. 21, 2007 <http://www.sciencedirect.com/science?_ob=ArticleURL&_u di=B6VB5- 455VM763&_user=10&_rdoc=1&_fmt=&_orig=search&_sort =d&view=c&_acct=C000050221&_version=1&_urlVersion= 0&_userid=10&md5=c9d9b919f172d211bbad1839fd5d0afe • “Effect of Sodium Chloride on Bakers' Yeast Growing in Gelatin.” Aem.asm.org Dec. 21, 2007 http://aem.asm.org/cgi/content/abstract/43/4/757