Lactobacillus Acidophilus

[deleted-300536]

Hello. For my science fair project I am working with Lactobacillus. My experiment is to record how long does it take for the "good" bacteria in your body to die off using antibiotics. The question I have is how would I be able to grow Lactobacillus on an agar petri dish and which antibiotics would I be able to experiment with? Also, would this be considered antibiotic resistance?

[deleted-294464]

Very interesting idea for a project that is very testable.

With regards to your questions, yes, you will be able to grow Lactobacillus on a petri dish with MRS agar. I would suggest approaching a biology teacher at your school to help you order the agar.

As for which antibiotic to use, a common one that is readily available and works well with Lactobacillus. which you could start with, is penicillin. Studies going back to the 1940s have looked at how penicillin can inhibit Lactobacillus. The following paper, from 1957, looks at the disk method and how penicillin affects Lactobacillus:

http://www.ncbi.nlm.nih.gov/pmc/article ... 0-0024.pdf

The disk method would be an excellent way to run your experiment as it is easy to measure without expensive instrumentation.

[deleted-300536]

Thank you so much for your reply. I was also informed by my teacher that a common antibiotic I would be able to use would be one that comes from an aquarium. Which antibiotic do you believe would be it? And if I were to use penicillin, would I easily be able to purchase it or would I need to have a prescription with the help of a mentor?

[deleted-300536]

As a part of my science project, I am going to change the temperature in which lactobacillus will be incubated. Will this affect how effective penicillin will kill the bacteria? In normal conditions, meaning the average human body temperature (37 degrees Celcius) it takes about 2 weeks to kill the bacteria in the body. Will increasing the temperature make the bacteria more vulnerable and be easily killed or more stronger and harder for the antibiotic to kill?

[deleted-288920]

Hi There!

Sounds like you have been doing a lot of thinking about your project, that is awesome! You have asked some great questions. What is the hypothesis of your project? Is there anyway to incorporate the questions you have below into your hypothesis? For example, you could try growing the lactobacillus at different temperatures and seeing how well the penicillin works or if visually you can see any changes in how the bacteria is growing.

Do you have a procedure or project you are following? Are you testing using the Kirby Bauer method? Please let us know a little more about your project and procedure and we can give you additional guidance if needed.

Nikki

[deleted-300536]

For my science fair project, I am going to grow Lactobacillus Acidophilus. I plan to purchase the agar plates already made. I am having some trouble finding a place where I can purchase this agar. Is there any recommendations? Thank you

[deleted-288920]

Hi there!

Carolina Biologics is a great resource for students to buy things like agar for their projects, http://www.carolina.com/ however I checked and it doesn't appear they have MRS agar. I found some however on Hardy Diagnostics here https://catalog.hardydiagnostics.com/cp ... SAgar.html.

Since you are working with microorganisms, please check outhttps://www.sciencebuddies.org/science- ... ques.shtml. And if you have specific questions as you are growing your cultures, please check in with your science teacher.

I hope this helps! Please let us know if you need additional resources or have questions.

Nikki

[deleted-300536]

Thank you for the resources! I have already purchases the MRS Agar, but now I am having trouble with another order. I am going to also have to purchase penicillin powder and liquid, but there is Penicillin G and Penicillin Streptomycin Powder available. What is the difference between both? Which type do you recommend? I am going to add it to the agar plates and observe how long it takes to terminate all bacteria.

[deleted-288920]

What kind of experiment are you running? Are you doing the kirby bauer experiment? If so, I might suggest the premade penicillin discs found here http://www.carolina.com/microbiology-su ... nomy+discs. If you are trying to decide between the liquid or powder, liquid is probably going to be better since it is already prepared. I would also suggest going with Penicillin G. Penicillin streptomycin is a combination of 2 antiobiotics, one being penicillin and the other being streptomycin.

Hope this helps! Please let us know if you need more help.

Nikki

[deleted-71603]

Hello. Please keep all questions for your project in our thread so our experts can best help you based on what has already been discussed. Good luck, and thanks for using Science Buddies!

[deleted-300536]

I am beginning to work on incubating the lactobacillus with commercial yogurt. I believed that diluting the yogurt would be more helpful to spread it around the MRS agar with sterile beads. How much should the yogurt be diluted? Or would just the yogurt be just enough to spread it around?

[deleted-288920]

Since yogurt is pretty thick, I agree diluting it is best. Here are some things to consider when deciding how much to dilute.
1-what amount of bacteria are you adding to your yogurt culture? When you plate bacteria on agar, they grow in colonies, the more colonies on a plate, the more bacteria you have in your sample. I work with bacteria everyday and when I count colonies on plates I like to count 10-100 colonies, also known as colony forming units (CFU) and this is usually described as CFU/mL aka milliliter. This is easy to do without your eyes going crazy. I then keep in mind what my dilution was so I can calculate how much bacteria was in my original sample.
2-how long will the bacteria be in the yogurt before you dilute and plate it? Consider this when you dilute and how much it may have grown.

I hope this make sense as far as the math and calculations go. Please let us know if you have additional questions! Good luck, sounds like you are doing great.

Nikki

[deleted-300536]

Thank you for your help/advice! I found a step by step procedure on a part of my procedure. I will definitely have more questions to ask when I reach more into my experiment, your replies have really helped me! Thank you once again.

[deleted-300536]

I am now at the place in my project where I have added the diluted yogurt onto MRS agar at the serial dilution of 1:10000 and began to incubate them. The next step to my project is to add ampicillin. My first option was Penicillin G, but now I am working with ampicillin. I added 0.1ml of the dilution onto the plate, what is a recommendation of the amount of antibiotic I should add?

[deleted-288920]

Sounds like you are making progress! How are you adding the ampicillin? Are you adding liquid directly to the plate or using ampicillin discs? If you are using the disc method (Kirby Bauer) they come premeasured with a concentration of antibiotic. If you are adding liquid directly to the plate, you could consider trying different concentrations of antibiotic to see if there is a difference in the amount needed to kill the bacteria.

[deleted-300536]

How long do petri dishes last in the incubator? Is there anything I can do to help them last longer? I am asking this because I am detecting how long it takes for ampicillin to terminate lactobacillus. I know it generally takes more than 1 week and I was notified that agar plates begin to dry out after one week in the incubator.

[deleted-288920]

Agar plates will usually only last a few days in the incubator. The heat causes them to dry out. Over time, the bacteria you are putting on your plates will also utilize all the nutrients too.