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Bacterial growth
Moderators: AmyCowen, kgudger, MadelineB, Moderators
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itsalexaa
- Posts: 4
- Joined: Mon Feb 23, 2015 3:29 pm
- Occupation: Student: 10th grade
- Project Question: My science fair is about testing for antibiotics in organic and nonorganic meat products by observing bacterial growth over a period of time (7 days). I have prepared 10 petri dishes for each trial (I am doing 3 trials each with 10 petri dishes) with agar, and used cotton swabs to obtain bacteria from my mouth. However, my only concern is counting the bacteria. Because I am not using an incubator, bacterial growth is very slow. How could I estimate my bacterial growth?
- Project Due Date: March 2, 2015
- Project Status: I am finished with my experiment and analyzing the data
Bacterial growth
How do you know how many bacteria you started with prior to the experiment? For example, if I started with an empty sterile agar filled petri dish and just swabbed it with bacteria using a cotton swab, would it just be zero?
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skuzniewski
- Posts: 14
- Joined: Fri Feb 13, 2015 5:53 pm
- Occupation: scientist
- Project Question: to help answer science questions
- Project Due Date: n/a
- Project Status: Not applicable
Re: Bacterial growth
If the petri dish has sterile agar, then it will not contain any bacteria. The sterilization process will normally kill off any microorganisms. You might want to keep a negative control, i.e. the petri dish with the sterile agar and unswabbed. Over time, this should not show any bacterial growth. If it does, then that means that there is contamination or the sterilization process was not effective.
There are many ways to find out how many bacteria you start with. The simplest way is to use the spectrophotometer at wavelength 600 nm for the suspended bacterial inoculum. Another way is to do protein assay such as the BioRad®protein assay.
There are many ways to find out how many bacteria you start with. The simplest way is to use the spectrophotometer at wavelength 600 nm for the suspended bacterial inoculum. Another way is to do protein assay such as the BioRad®protein assay.
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deleted-132180
- Former Expert
- Posts: 302
- Joined: Thu Apr 04, 2013 12:27 pm
- Occupation: Graduate Student
- Project Question: I am volunteering for the "Ask an Expert" program.
- Project Due Date: I am volunteering for the "Ask an Expert" program.
- Project Status: Not applicable
Re: Bacterial growth
Hi there,
I'm slightly confused by your question. What is your question and hypothesis, and what is the experiment you're doing to address it? Like the previous expert mentioned, if you start with an empty sterile agar plate, there should be no bacteria on that plate unless it was contaminated. What do you mean by swabbing the plate with bacteria using a cotton swab and that it would be zero? If you streak bacteria onto the plate, then the plate will no longer be sterile and there will be bacteria on it. You just have to wait a day or two before colonies show up so you can count how many are on the plate. Why do you need to know how many bacteria you have before your experiment? If you give us more details about your experiment, we can provide you with more helpful advice.
Connie
I'm slightly confused by your question. What is your question and hypothesis, and what is the experiment you're doing to address it? Like the previous expert mentioned, if you start with an empty sterile agar plate, there should be no bacteria on that plate unless it was contaminated. What do you mean by swabbing the plate with bacteria using a cotton swab and that it would be zero? If you streak bacteria onto the plate, then the plate will no longer be sterile and there will be bacteria on it. You just have to wait a day or two before colonies show up so you can count how many are on the plate. Why do you need to know how many bacteria you have before your experiment? If you give us more details about your experiment, we can provide you with more helpful advice.
Connie