Science Buddies: "Ask an Expert"

Hi, I purchased liquid E coli 12 from Carolina along with Nutrient rich agar plates. I swabbed in a Y shape on each of 9 plates. I wanted to test the antibacterial effects of cinnamon and honey. I placed a disk coated in cinnamon in each quadrant of two plates. I placed a disk coated of honey in each quadrant of two other plates. I placed a sterile disk in each quadrant of two control plates.

I can see the Y where the e coli was streaked on each plate. I kept the plates at room temperature. I know that was my mistake. I should have incubated them at 98.6F (body temperature). I was hoping the e coli would still grow eventually at room temp. It's been 22 days and I don't think the e coli "grew". I was expecting the Y to expand like a "lawn'" and it didn't on any of the 6 plates.

I am really not a science person so I don't really know what I am seeing.

This is what happened -
1) The control plates as well as one of the cinnamon plates are exactly as they looked 3 weeks ago. Comment? Nothing's growing because it's not hot enough and so sterile there is no other accidental bacteria contamination to grow?

2) The other cinnamon plate has a white circle in one quadrant and two white circles in another quadrant which are slowly growing. They are 6mm in diameter now. Cool that they are in almost perfect circles. Is this bacteria? Is this e coli? It is bright white not the foggy clear of the e coli Y that I streaked. Could this be something that accidentally got on the plate when I was streaking e coli? The white circles are nowhere near the Y or the cinnamon disks.

3) The honey plates look vastly different. On the first honey plate around the honey disks is a cloudy film growing around the honey disks, not in an exact circle just a blob. They are separate from the Y. The e coli Y remains the same as from the start.

4) The second honey plate is very interesting. It has the same blobs of foggy film around the honey disks and the Y is not expanding but the dish also has a lot of black to grey mold growing in it. The mold is avoiding the foggy film areas.

5) Do you think the e coli is dead now or do you think it still has a chance to grow? Should I try to incubate it now? I am assuming it is dead. I do notice tiny white lines sprouting off the Y lines in the control dishes but I think they were there from the beginning.

6) Although they look very clear in my picture the cinnamon and honey dishes are tinting tan while the control are still very clear. Is the cinnamon/honey diffusing into the agar?

I know, I know I should have heated the plates. But, could you comment on what I can say about what I see? I do not have the time, money or energy to redo my experiment and I have to draw conclusions. I will have to take a 0 for the data/graph part of my grade but I need some analysis. Please help.
I have desperately tried to attach a picture but I just can't. First attempts error message said file to big. Next attempts it won't accept jpg or png. I opened a pic in Word and saved as a Word doc. When I tried to attach it said "Sorry, the board attachment quota has been reached." But I hope I gave you enough detail to help me out.
Thank you, Timbio

Hi Timbo,

Sounds like you put a lot of work into this experiment - good job! Also, you have thought it out pretty well - I can make some comment sofr you to help you along.

1) I agree with what you wrote, the colonies don't seem to be expanding.
1) The control plates as well as one of the cinnamon plates are exactly as they looked 3 weeks ago. Comment? Nothing's growing because it's not hot enough and so sterile there is no other accidental bacteria contamination to grow?

2) This sounds like mold to me - it could have landed there from the air while you were working.
2) The other cinnamon plate has a white circle in one quadrant and two white circles in another quadrant which are slowly growing. They are 6mm in diameter now. Cool that they are in almost perfect circles. Is this bacteria? Is this e coli? It is bright white not the foggy clear of the e coli Y that I streaked. Could this be something that accidentally got on the plate when I was streaking e coli? The white circles are nowhere near the Y or the cinnamon disks.

3) This also sounds like a microbe contaminant. The e. coli colonies you are looking for a little tan-colored domes.
3) The honey plates look vastly different. On the first honey plate around the honey disks is a cloudy film growing around the honey disks, not in an exact circle just a blob. They are separate from the Y. The e coli Y remains the same as from the start.

4) 4) definately mold if black. It sounds like the honey also has anti-fungal properties - can you confirm that with a google search?
4) The second honey plate is very interesting. It has the same blobs of foggy film around the honey disks and the Y is not expanding but the dish also has a lot of black to grey mold growing in it. The mold is avoiding the foggy film areas.

5) The colonies are likely dormant - if you scrape them off and into a liquid medium, with some shaking at body temp, they will grow againa nd you could re=plate it. I don't think I would try to continue with this experiement since you have mold contamination and the e.coli have been dormant for a while.
5) Do you think the e coli is dead now or do you think it still has a chance to grow? Should I try to incubate it now? I am assuming it is dead. I do notice tiny white lines sprouting off the Y lines in the control dishes but I think they were there from the beginning.

6) They could be diffusing into the agar and changing it's color.
6) Although they look very clear in my picture the cinnamon and honey dishes are tinting tan while the control are still very clear. Is the cinnamon/honey diffusing into the agar?

I feel what you can say in the experiment is that the control didn't work and you have mold contamination, so need to do it again to have good data. But you can still show your project and the results you got since you learn a lot from doing this - but you weren't able to prove or disprove your hypothesis based on this one experiment.

Also - you might want to read through this post, as Donna gives some great advice: https://www.sciencebuddies.org/science- ... php?t=5309

Let me know if you have further questions.
Tonya

Hello Timbio,
I agree with the previous expert that you have done a very good job of summarizing your experiment and results. I would hope that you might get some credit for the data/graph portion of your report if you made a graph showing time on the horizontal axis and show the zero growth on the vertical axis! Results like yours happen all the time in science in the real world. You've demonstrated how much one can learn even when things go wrong! Best wishes!