Last week's biofilm tests had invalid (and unreadable) data due to the agar plates evaporating, but I re-did the 24-hour biofilm tests for e.coli and a solution of 10 mg/mL Dawn and now we have numbers! Woot! The only big difference between last week's biofilm tests and those for this week was that rather than letting the plates sit in the hood for the weekend, we just put them in the incubator overnight to keep the pesky agar form going awry. Below are some pictures of the plates after counting colonies:
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| My beautiful plates! |
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| E.coli Dawn challenge plates |
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| E.coli control plates |
The Dawn had a HUGE effect on the quantity of e.coli biofilms.
For example, a plate count we used for the 1st control group was 3.9E7 CFU/mL.
The corresponding Dawn challenge enumeration was 4.8E4 CFU/mL.
The CFUs/mL for the 2nd group control and Dawn, respectively, were 1.8E7 and 4.62E5.
And for the 3rd group: 5.9E6 and 2.26E5.
This means that the Dawn detergent is greatly decreasing the quantity of plated colonies. However, we do not know whether this concentration of detergent is killing the bacteria in the biofilms or if it is just sweeping them away. I will probably not have time to perform that kind of test, but based on the MICs, we are fairly sure that the detergent is sweeping the bacteria away. It's interesting to see that the Dawn is actually having an effect on the e.coli biofilms, as this was fairly unexpected. But don't make any assumptions yet! I will probably decrease the concentration of detergent to a more realistic figure, like 5 or 3mg/mL in coming weeks.There is also a pretty good chance I will do this exact thing again with this different concentration.
I haven't really had many obstacles except for getting used to the procedures, and everything seems pretty smooth.This kind of procedure is probably what you guys will be seeing for the remainder of my project. But don't worry! I will test different types of bacteria with different types of detergent, so hopefully, you'll have an update on that every week.
до четверга (until Thursday),
Mackenzie
Hi Mackenzie,
ReplyDeleteResults!! How exciting!
What do you mean by "sweeping" the colonies away?
:) Instead of penetrating the biofilms, the detergent might just pick it from its surface (like tearing a snail off a rock)and let it float away somewhere else.
ReplyDeleteI think in the coming weeks, I am going to perform separate dilution and enumeration tests to figure out if that is what's really happening.
So the problem with your plates before had to do with it being in the hood?
ReplyDeleteAnd what is enumeration?
Pretty much. In Arizona, you have to take extra measures to keep bacteria and agar from drying up because the air is so dry. Also, the hood includes a kind of fan to keep from contaminating the entire lab, and that fan makes things in the hood more prone to evaporation.
ReplyDeleteEnumeration is just diluting the bacteria, placing it on agar plates, and then in the morning when the bacteria have grown, counting the colonies.