It was observed by many employees at a local supermarket that their hands were commonly dirty after handling money. A question arose in that is the money really dirty and contaminated with bacteria. While other research has been done on other fomites transferring bacteria to other surfaces, little research has been done in investigating the microbiology of money. The use of money to pass pathogenic bacteria could be a way for bacteria to infect the general population. One study done on dollar bills showed that 94% of dollar bills were contaminated with bacteria (Pope, et. al. 2002). No current research can be found on the microbiology of coins. American coins are made of three basic metals. Those metals are copper, zinc and nickel. Metal has been shown to inhibit bacterial growth in solution (Andrade et. al. 2004, Makarov et. al. 2004). Quarters and Dimes have the same inner core of zinc and the same outer layer composed of 75 copper 25 nickel alloy, but are different sizes. Nickels are made entirely of the outer core alloy that quarters and dimes are made of. Pennies are made of zinc plated copper. These varying compositions of metal may affect the amount of bacteria present. The presence of metal around bacterial cells can be a toxic situation for the organisms. This research examines if microbes are found contaminating coins, what common subgroups of organisms are found, and if there is a significant difference between the four coins. Based on observations and past research, the coins will contain microbial organisms and there will be a difference between the number of coins contaminated. Are Microorganisms Present on Commonly used Coin Currency? Results Material and Methods Collection of Samples 40 petri dishes (10 each coin) used to collect samples Sterile forceps used to hold coin Cotton swab was dipped in nutrient broth and then swabbed covering entire area of coin Cotton swab placed back into broth and incubated Streak Plating Observations Based on cell shape, size, and color; if plate had growth a smear was made Discussion The proportion of coins that had microbes present varied among the four coins. Nickels had the most coins with contamination present on 6 of the 10. The four types of classes of organisms found were G+ cocci, G+ rod, G-rod and Yeast. Most of the organisms found were Gram positive cocci and Yeasts. These two organisms are common skin resident and transient organisms. The Gram positive cocci organisms are probably some species of Staphylococcus based on their cluster formation seen in the Gram stain. These organisms have been known to cause infections in susceptible people (Solberg 2000). A difference in each coin’s ability to provide host for bacteria depend upon the metals each contains. Quarters and dimes are made of the same material. Because of the size difference it was expected that quarters would have greater contamination, however the inhibiting effects were greater in quarters leading to less contamination. Metals such as zinc have been shown to inhibit growth of bacterial organisms in past research (Andrade 2004, Makarov 2004). All coins except for nickel have zinc in them. This may be why nickel has the greatest contamination. Conclusions- Each type of coin did contain microbes and nickels had the most contamination. The four types of microbes found were G+ cocci, G+rod, G- rod, and Yeast. Introduction Purpose To determine if microbes are present on quarters, dimes, nickels and pennies. To identify classes of organisms on each contaminated coin. To test null hypothesis that there is no difference between 0/10 and the coin samples. There were 16 coins that had contamination on the 40 coin samples. Using a measure of proportions using the z-statistic (Triola 2001) it was found that quarters and pennies were found to have a significance level of.02 suggesting there is no difference between null hypothesis and coin contamination. Dimes were found to be significant at the.01 level. Nickels were highly significant at the.001 level. Dimes and nickels reject null hypothesis. Laura Bednar Department of Biological Sciences York College of Pennsylvania Literature Cited Andrade LR, et. al. Effects of copper on Enteromorpha flexuosa (Chlorophyta) in vitro. Ecotoxicology Environmental Safety. May Makarov AA, et. al. Zinc (II)-mediated inhibition of ribonuclease Sa by an N- hydroxyurea nucleotide and its basis. Biochem Biophys Resource Communication. June Pope, Theodore W. et. al. Bacterial Contamination of Paper Currency. Southern Medical Journal. December Solburg, Claus. Spread of Staphylococcus aureus in Hospitals: Causes and Prevention. Scandinavian Journal of Infectious Diseases. March Triola, Mario F. Measure of proportions using the Z-statistic. Elementary Statisitic 8 th edition Acknowledgements Dr. Mathur, Mentor Mrs. Taylor A loopful of broth was taken and a streak plate was made Gram Staining Once smear was made Gram stain was done following Standard procedure