battle of the sexes: dorm life bacteria

This topic submitted by gretchen culbertson, jamie lipps, leslie marticke, britni rex ( rexbn@muohio.edu ) on 12/9/04 .

Natural Systems 1 Syllabus---Western Program---Miami University

Battle of the sexes:
Dorm life bacteria
Gretchen Culbertson
Jamie Lipps
Leslie Marticke
Britni Rex
9 December 2004

Abstract

Many scientific researchers have studied the growth and effects of bacteria in order to provide individuals with important knowledge. In our lab, we studied bacteria in one of the most commonly used areas on a college campus, dorm rooms. We collected samples from both male and female door room door handles in hopes of finding a difference in the amount of bacteria between the two genders. To complete our experiment, we did a preliminary test to determine the most efficient way to sample bacteria. After one week, we analyzed the results of the preliminary samples, and decided to swab the entire surface of the door handle and opposed to a single, specified area. For the final sample collection, we swabbed 15 door handles for each gender, adding 1mm of the solution to each of two Petri dishes from each sample. Lastly, we added 5mm of the same solution from the final sampling to new Petri dishes in order to achieve better results. By comparing the data from each of the samples, we were not able to reject our null hypothesis. The results of our experiment showed there was not a significant difference in the amount of bacteria present on male dorm room handles compared to a female doors.

Introduction

The purpose of this lab is to discover the amount of bacteria present on college campus dorm room handles, and if there is a difference in the amount of bacteria present between male and female rooms. Our null hypothesis is that we expect to find the same amount of bacteria present on both male and female room handles. Some questions we will be asking throughout this experiment are: what amounts of bacteria are present on college dormitory room handles? Does the difference in personal hygiene among male and females result in a larger amount of bacteria? We hypothesize that since we will be collecting samples from the roomsÕ outside handles, there will be a difference in the amount of bacteria present on male handles as opposed to female handles, because we feel females have a greater sense of hygiene.

Our interest in this topic derived from our change of personal rooms to multiple occupancy rooms. As college students, we are susceptible to various forms of bacteria, which put us at risk for infection. We want others to be aware of any potentially harmful types of bacteria, if any exist.

Background Information

Bacteria are among the earliest life forms, and are thought to have appeared billions of years ago. ÒAs do other organisms, all bacteria require nutrients for growth and multiplication. The supply of nutrients is essential and is a prerequisite for the synthesis of cell material and the generation of energyÓ (Balows 1981, p. 138). They are single celled microorganisms that eat anything from sugar and starch, to sunlight, sulfur and iron. Bacteria create atmospheric oxygen that enables other forms to develop, such as mitochondria, which are responsible for creating energy for body cells. Most bacteria are moderately harmless, in that they make medicine, break down oil from oil spills, make about half the oxygen we breathe, and they are the main foundation of the food chain that feeds all life on earth. Bacteria form in 1 out of 3 shapes from rod or stick-shaped bacilli, to little balls called cocci (Cullimore 2000, p. 13). They live in or on every part of Earth from the soil, to the water and the air.

Temperature, hydrogen ion concentration, carbon dioxide, light, and hydrostatic pressure influence the growth and development of bacteria. The nutritional and environmental conditions selectively favor the development of those organismsÕ best adapted to the given conditions. So, unless one knows what bacteria are present, it is difficult to grow them under specific conditions (Balows 1981, p. 145). One of the most important conditions is temperature. There are three cardinal temperatures for every type of bacteria, the minimum growth temperature, optimum growth temperature, and maximum growth temperature. At the optimum temperature, growth occurs at the maximum rate (Balows 1981, p. 145). Difficulties in growing bacteria in isolation are encountered whenever the conditions for growth are unknown. If we are more intellectually attuned to the amount of bacteria our bodies encounter on a daily basis, we may be able to protect ourselves against unwanted infections. We may also be more likely to partake in precautionary measures against bacterial infections such as hand-washing and healthy eating habits.

Research Design

First, we met with Dr. Hooke, the head of the microbiology department, to obtain the materials we needed throughout our experiment. Once we had all of the materials we need to successfully carry out our experiment, we began collecting our data. We collected our first six samples on Tuesday, October 19. The purpose of these preliminary samples was to discover the best way to ensure good results. We took three samples from both boyÕs and girlÕs dormitory rooms, totaling six samples. We also made sure that each room only occupied two residents. The samples measured 1 cm, 1 inch and the entire outside dorm handle.

To collect the data we used a sterile cotton swab. First we dampened the swab in distilled water and squeezed the excess out along the inside of the appropriately labeled test tube. Then we gently brushed the door handle, making sure to cover the entire desired area. The swab was then put back in the same test tube and stirred around vigorously. The swab could then be disposed and the tube secured with cap. Once all test tubes were filled, we transferred half of the solution into a clean Petri dish that was correspondently labeled to match the tube it came from. After allowing these samples to grow for one week in a dark warm environment, we analyzed the results by rating them based on a 1 to 10 scale and took pictures. Based on our results we determined that swabbing the entire doorknob would be best.

Next, we again met with Dr. Hooke and gathered more materials. On Thursday October 28 we began collecting new data in Peabody Hall, again making sure only two people occupied the rooms. We collected a total of 30 samples, 15 boyÕs and 15 girlÕs rooms (each room had two dishes assigned to it equaling 60 dishes). We used the same technique of swabbing, doing the entire handle only this time. After advice from Dr. Hooke we also only used 1 milliliter of the solution in the Petri dishes. These were allowed to grow for one week as well.
Unfortunately these samples did not produce the results we had hoped for. So we then decided to start over. Due to lack of time and material we collected only 10 samples from both boys and girls and used only one Petri dish, totaling 20 dishes. We also put them in a warmer darker place and used 5 milliliters of solution in the dishes. These were grown for a week and more pictures were taken using the rating scale. We then further allowed them to grow for yet another week and took more data.

Methods

In order to achieve success in our lab experiment, we met with Dr. Hooke, head of the microbiology department, to discuss the procedure for cultivating, identifying, and comparing various forms of bacteria and to obtain materials for testing purposes.

SWABBING TECHNIQUE: First we rinsed the sterile swab in distilled water and squeezed the excess out along the inside of the appropriately labeled test tube. Then we gently brushed the door handle, making sure to cover the entire desired area. The swab was then put back in the same test tube and stirred around vigorously. The swab could then be disposed and the tube cap secured. Once all test tubes were filled, we transferred the appropriate amount of solution into a clean Petri dish that was correspondently labeled to match the tube it came from. Then they were allowed to grow for a week.

Materials

-Latex Gloves
-Masking Tape
-sterile swabs (40) (4 of these are extra just incase a few are dropped)
- sterile test tubes w/ 10 mL of sterile solution in each (40) (4 of these are extra)
-Petri dishes w/ agar gel prepared in each (90) (4 of these are extra)
-Pipette-man
-sterile pipette tips (100)
-Jump Software
-recording sheets

Research Time-line

Tues Oct. 12- Collect materials for lab experiment from microbiology department
Tues Oct. 19- took 6 samples (3 of each gender) and put in Petri dishes
Thurs Oct. 21- let bacteria grow
Tues. Oct. 24- took pictures
Tues Oct. 26- collected more materials for rest of experiment
Thurs Oct. 28- collected new samples
Nov. 1- Nov 7- start 15 samples/ 2 Petri dishes for each sample
Nov. 8- Nov. 14- started over with 10 samples per gender/ I Petri dish per sample
Nov. 14- Nov. 28- Let samples grow and analyzed Petri dishes
Nov. 29- Dec. 5- Analyze data and begin writing results and conclusion
Dec. 6- Dec. 12- Prepare final lab for submission

Results

The following is a sample data table from the two observation dates.
Number of Petri Dish/ Bacteria Count 11-23-04/ Bacteria Count 11-30-04
1 8 9
2 3 3
3 5 8
4 3 3
5 1 1.5
6 4 7
7 7 8
8 0 2
9 1 1
10 2 2
16 .5 .5
17 1 1
18 .5 7
19 4 5
20 5 7
21 5 6
22 7 8
23 0 .5
24 5 8
25 6 6.5

To determine the amount of bacteria present in each of the Petri dishes, we used a rating scale from one to ten, one representing the smallest amount of bacteria and ten being the most. The bacteria amounts were rated on two different dates: November 23rd and then on November 30th. The following graphs represent the change in amount of bacteria observed on each date, for both girls and boys.

The next graph depicts the comparison of bacteria amounts for females and males found on each observation date.

Using Jump Software, we compared the data from each of the given observation dates to determine if there is a significant difference in the amount of bacteria present on female dorm room door handles compared to males.

Sources

www.microbes.info
-Introduction to microbes.
www.cellsalive.com
- Descriptions, pictures, and definitions.
www.microbe.org/microbes/bacterium1.asp
-Background information and definitions.
www.ucmp.berkeley.edu/bacteria/bacterialh.html
-Additional links and resources.
www.earthlife.net/prokaryotes/bacteria.html
-Pictures, "friends and enemies," and diseases.
Bakalar, Nicholas. Where the Germs are: a scientific safari. Hoboken, N.J.:Wiley, 2003
-Microorganisms, bacteria, and germ theory of disease.
Berg, Howard C. E.Coli in Motion. New York: Springer, 2004
-Microogransims, motility, and e.coli
Balows, A., Schlegel, H., Starr., Stolp, H., Truper, H. The Prokaryotes: A handbook on Habitats,
Isolation, and Identification of Bacteria. Springer-Verlag Berlin Heidelberg, 1981.
-bacteria identification
Cossart, Pascale. Cellular Microbiology. Washington, D.C. : ASM Press, 2000
-Cell biology: An overview, bacterial adherence to surfaces, bacterial toxins, and infection.
Cullimore, Roy. Practical Atlas For Bacteria Identification. CRC Press. 2000.
-bacteria identification
Dyer, Betsey Dextes. A Field Guide to Bacteria. Ithaca, N.Y. : Cornell University Press, 2003
-Bacteriodes, gliders, and their relatives.
Godish, That. Indoor Environmental Quality. Boca Raton, Fl. : Lewis Publishers, 2001
-Indoor air pollution, housing and health, and industrial hygiene.
Krasher, Robert I. The Microbial Challenge: Human Microbe Interactions. Washington, D.C. :
ASM Press, 2002
-The beneficial aspects of microbes, bacterial diseases, and the immune response.
Majerus, Michael E.N. Sex Wars: Genes, Bacteria, and Biased Sex Ratios. Princeton, N.J. :
Princeton Univeristy Press, 2003
-Sex ratio, and host bacteria relationships
Mulchandani, A., O. Sadik. Chemical and Biological Sensors for Environmental Monitoring.
Washington, D.C. : American Chemical Society, 2000
-Chemical detectors and environmental monitoring.
Ofek, I., D. Hasty, R. Doyle. Bacterial Adhesion to Animal Cells and Tissues. Washington, D.C.
: ASM Press, 2003
-Basic concepts in bacterial adhesions.
Raineri, Deanna. Introduction to Molecular Biology. Malden, MA.: Blackwell Science, 2001.
-Illustrations, questions, and answers.
Reeve, Eric. Encyclopedia of Gentics. London: Fitzroy Dearborn, 2001
-Genetics of bacteria and viruses.
Walters, Mark Jerome. Six Modern Plagues and Now We Are Causing Them. Washington:
Island Press/Shearwater Books, 2003
-Salmonella, the travels of antibiotic resistance, and environmental health.
Wilson, M., R. McNab, B. Henderson. Bacterial Disease Mechanisms: An Introduction to
Cellular Microbiology. Cambridge, N.Y. : Cambridge University Press, 2002
-An introduction to bacterial diseases, immune defenses against bacteria, and bacteria in human health and disease