Bacterial Growth on Different Types of Doorknobs

Morgan Crouch

Biology-Health Science Major
Department of Biology
Tennessee Technological University
Cookeville, TN 38505
 

Table of Contents

1.) Title (pg. 1)
2.) Table of Contents (pg. 2)
3.) Project Summary (pg. 3)
4.) Key Words (pg. 4)
5.) Introduction (pg. 5)
6.) Methods and Materials (pg. 6-8)
7.) Expected Results and Benefits (pg. 9)
8.) Project Timeline (pg. 10)
9.) Literature Cited Page (pg. 11)
10.) Budget (pg. 12)
 

Project Summary

          With an increase in contact, it is likely that there will be an increase of infections and disease. Bacteria can live in many different areas. The main question in this experiment that arises does the type of different metals effect the growth of bacteria on the metal doorknob. The objective is to better understand the growth of bacteria around the different types of metal doorknobs. This is done by taking samples from a control and others from the doorknobs used everyday, then the bacteria will be cultures on a trypticase soy agar (TSA) medium to test if there is any growth of bacteria and if it differs between the different types of metal. The goal of this experiment is to show how the type of metal effects bacterial growth on the doorknobs.

Keywords

• Bacteria
• Growth
• Doorknob
• Culturing Bacteria
• TSA Medium
 

Introduction

In today’s society, many diseases arise from bacteria that grow everywhere. Research is constantly done to try to fight the disease-causing bacteria. Through new research, scientists have shown though that the bacteria can grow on different types of metal. It also can prevent corrosion of metals in specific conditions (Mansfield 2007).
Since it is known that bacteria can grow on metal surfaces, can different types of metals affect the amount or the rate in which the bacteria grown. If stainless steel produces less bacteria than say brass, it would make more sense to use this metal where people are in danger of catching different diseases, for example a hospital or a doctor’s office.
I will disprove the Null hypothesis by proving that different types of metals can indeed affect the growth of bacteria on that metal. Doorknobs will be tested and compared on Tryptic Soy Agar (TSA) plates, this will show that bacteria does live on the doorknobs we use everyday. The objective of my research is to show the effect that the type of metal has on the amount of bacterial growth on that metal doorknob.

Methods and Materials

The experiment will be done taking samples from around six different door knobs of Pennebaker hall and by also taking six control samples.  The control of the experiment is taking samples from door knobs that have been covered so they will not be contaminated, but the same doorknob none the less.  Also in the experiment samples will be taken from doorknobs that have been sanitized at the beginning of the experiment and then the samples will be taken a few days later.  The experiment design/scientific method matrix of the project is shown in Table 1.  The materials that are needed for this experiment are 6 Petri dishes, 6 Tryptic soy agar (TSA) plates, 6 Sterile Cotton Swab, Vespene, 3 plastic door knob covers,  1 Inoculating Loop, and an Incubator. 

Scientific Method Matrix

Figure 1

The process behind this experimental method is relatively simple.  First label a sterile TSA plate with a sample number.  Once the plates are labeled correctly the proper way to handle the agar plate must be learned.  The correct way to handle an agar plate is to pick up the bottom of the plate with the agar leaving the lid on the counter.  The plate should be held vertically while you streak it, to inhibit airborne contaminants.  Do not open the plate until you are ready to streak the first section and set it back down in its lid immediately after finishing.  Next, take one sterile cotton swab and moisten the swab with distilled water.  Then take the cotton swab and swab around the doorknob or control doorknob.  Rub the swab over the area to be sampled, turning the swab so that all sides contact the surface.  After your sample is taken inoculate a small section of the TSA with your sample.  Again rotate the swab so organisms from all sides get onto the plate, but be careful not to dig into the agar.  Discard the cotton swab into the jar of Vespene.  Then take your inoculating loop, sterilize it by placing the loop into a flame and then allow the loop cool.  Once the loop is cooled streak the next section of the plate.  You will pick up bacteria from the first section with your first few streak lines, and then dilute them by making a zigzag streak line without going back into the first section again.  Flame your loop again and streak the rest of the plate as in the step directly above.  Each time you start a new streak line, be sure to go over the previous streak two of three times to pick up bacteria, then dilute the bacteria by finishing the streak without crossing previous lines.  Make sure that your plates are labeled properly and place them in the incubator for a few days.  Place the plates in the incubator with the agar side up to prevent condensation on the surface⁶. Each sample must be cultured in separate TSA plates. 

All data from the samples are recorded on the data sheet and then analyzed them further.  The data from the samples were taken and then the mean was found from the control doorknobs and the samples around the contaminated doorknob.  Then the standard deviation is taken and then the t test is done.

Data Form

Bacterial Growth on Different Types of Doorknobs

Sample: _______________________________________________________________

(Contaminated or Control Doorknobs)

Sample Taken By: ____________________________________________________

                              (Name)                                 (Position)

Remarks: ____________________________________________________________

Signature: __________________________________________________   

Date: ________________________

Expected Results and Benefits

The expected results of this experiment are that I hope to find that there will be bacteria growth on the contaminated doorknobs.  I also hope to find that there is a significant difference in the growth of bacteria from samples taken from the contaminated and the control doorknobs. I also hope to find that the amount of bacterial growth is different for each type of metal doorknob. This project is very beneficial because it will help people decide which type of metal will help control the growth of bacteria and that could help hospitals, doctor offices, and even schools control different diseases.

Personnel

Dr. Susan Goss and Morgan Crouch

Resume will be inserted after midterm.

Ethics Statement

Ethics statement will be inserted after midterm.

Timeline

Literature Cited

1.) Mansfield, Florian. The Interaction of Bacteria and Metal Surfaces. Electrochimica Acta: 52(27): 7670-7680.

 2.) Goss, Susan. Health Science Microbiology Laboratory Manual. Exercise 4: Isolating and Growing Microorganisms in the Laboratory Fall 2005.

Budget

                                       HΦΜE                                                                    Biology 3920