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MaryM
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hands?
mouth?
toilets?
kitchen sinks?
We are going to be doing the "grow bacteria in petri dish" experiment in our co-op and I want to maximize the probability of good bacterial growth. I've had it not grow that well before when I did it way back years ago.
So help me find the most bacteria laden sources.
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Mary M. in Denver
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kristacecilia
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I have read that your kitchen sink has the most. :O
Public washrooms are good. When I took microbiology we got the women's public washroom in our building for sampling. Gag.
Mouths are are always a bacterial hotbed.
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kristinannie
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The showers at the frat house across the street from my sorority beat all the bacteria infested locations we tried on our campus.  I would go into a gas station bathroom. Nasty!
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Mackfam
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Do you have access to an incubator? That could explain why you might not have had good bacteria colonization. If you don't have an incubator, it will take longer for the bacteria to colonize...so maybe just be prepared to wait a little longer to observe and examine?
I'd definitely culture the mouth!! But I'd swab some other sources, too - like the doorknob, keyboard, their cellphone, toilet, the handle on a bathroom stall (  ).
An extension of this is to mark the bottom (outside) of the petri dish in a small area with a 1/2" diameter circle (using a sharpie), and after swabbing, use a sterile Qtip dipped in alcohol and just dab within that circle. It's REALLY fun to draw a few circles, and with separate Qtips, and after swabbing the entire petri dish with bacteria source, dab with hydrogen peroxide, alchohol, popular hand sanitizer within the circles. There is one source that DEFINITELY kills more bacteria!
We didn't culture bacteria in a petri dish, but we had great success with the mouth for a source of DNA when we recently did a DNA Extraction Lab.
There is this Bacteria science guide from homeschool science.
And...surely you've already seen this....but there's a neat and helpful Steve Spangler guide to growing bacteria in a petri dish.
Take pics and let us know how it turns out!  Or am I the only person that would be thrilled to see colonies of bacteria growing??????
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Mackfam
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More....
Swab in the nose with a moist sterile Qtip for a good sample of bacteria/flora. Best sources are going to be moist because they'll be most likely to transfer bacteria more readily.
You might get more bacteria colonization on the plate if you allow the bacteria to really get rolling in a sterile broth first. This site has a good explanation for culturing bacteria using sterile broth as a step. I know they talk about use of a wire loupe, but you can still use the sterile Qtip. Luria broth would be an option. Swab like normal, allow bacteria to grow for a few days/week within the vial of broth....then swab from Luria broth onto petri dish. You might have more colonization with this head start. The drawback is that you'd need a single vial of Luria broth for each bacteria source you swab, and that could get $$....and I'm not sure how many you're going to try to work with. But, it might be worth it to at least try to get a head start on growth this way. In the end, it could yield more results. I haven't tried it yet though...so I reserve the right to be wrong! 
Also, if you don't have access to an incubator, place petri dishes in sealed ziploc bags on top of the fridge (consistent warm temp)....or on top of a your water heater if yours is INSIDE (ours is in the garage so this doesn't work for us.) This should bump and hold temps to encourage bacteria growth. No matter what, the growth wil be much slower than if an incubator is used. Do you have any contacts at the local university Biology lab to ask if you could borrow space in their incubators for a week?
You may already be mapping the petri dish, but a numbered sharpie grid on the bottom of the petri dish can then be duplicated in a lab book, and gives a good map for recording results.
Mackfam wrote:
| An extension of this is to mark the bottom (outside) of the petri dish in a small area with a 1/2" diameter circle (using a sharpie), and after swabbing, use a sterile Qtip dipped in alcohol and just dab within that circle. |
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Goodness, there are so many fun directions to go with this. Another idea would be to use a hole punch and punch some small paper disks (scientific filter paper works, but so do coffee filters) and then moisten/soak them in different solutions (liquids work better than gels for this):
** vinegar (is NOT a good killer of bacteria)
** hydrogen peroxide (very effective)
** alcohol
** iodine
** soap and water solution (actually NOT effective at all for killing normal flora  )
Drop the soaked paper disk in the petri dish. Either draw a circle and label, or note the mapped area for the disk soaked in a particular fluid. There should be visible results of bacteria inhibition in the areas of some of the paper circles (peroxide and alcohol)...while not in others (soap and vinegar).
This will only work well if you get good bacteria colonization on your petri dishes, but if you do, you should REALLY be able to see some significant results from this and it's an easy and inexpensive way to extend this lab into two - bacteria colonization & evaluating bacteria growth inhibitors.
Ok. I'm done serial posting about bacteria growth.
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cvbmom
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TV remote or telephone are my guess. Maybe doorknob?
Christine
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Mackfam wrote:
More....
You may already be mapping the petri dish, but a numbered sharpie grid on the bottom of the petri dish can then be duplicated in a lab book, and gives a good map for recording results.
Mackfam wrote:
| An extension of this is to mark the bottom (outside) of the petri dish in a small area with a 1/2" diameter circle (using a sharpie), and after swabbing, use a sterile Qtip dipped in alcohol and just dab within that circle. |
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Goodness, there are so many fun directions to go with this. Another idea would be to use a hole punch and punch some small paper disks (scientific filter paper works, but so do coffee filters) and then moisten/soak them in different solutions (liquids work better than gels for this):
** vinegar (is NOT a good killer of bacteria)
** hydrogen peroxide (very effective)
** alcohol
** iodine
** soap and water solution (actually NOT effective at all for killing normal flora )
Ok. I'm done serial posting about bacteria growth. |
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Jen! How do you learn SO much about all of this? Are you a serious homeschooler or what?! 
I really want to be Jen when I grow up... 
I so need a kick in the right direction for being more serious with science...there is so much! Where do you find your focus for science??
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guitarnan
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Catholic grade school bathroom. Wish I were kidding!
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lapazfarm
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Soil is usually a great source. Get some good, rich soil, add it to some water, shake well, and then filter.Use the filtrate as your sample.
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MaryM
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Thanks for all the ideas, ladies. We will give several a try and hope for good growth!
Jen, I never knew you were such a bacteriaphile - who would have guessed.... 
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lapazfarm
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btw, do you have prepared petri dishes? If so, what is the substrate? I find nutrient agar works best for home experimentation.
Also, a word of caution. If you swab bathrooms or mouths, etc, please make sure you seal the petri dishes tightly with tape, and don't open them during the experiment. Dispose of used dishes properly--add bleach to each dish to kill bacteria, and seal in plastic bag.
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MaryM
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I'm preparing the petri dishes - it is nutrient agar - got it from The Science Company, here in town. Thanks for the caution info - I had heard in general they should be taped and not opened, so will be very careful with any mouth or bathroom swabs.
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AtHomeScience
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I just have to comment on Jen's fabulous post, especially the chemical-soaked discs placed on the colonies. It brought me back to my medical technologist days! The loupes streak the culture material on the plate, but they are mostly convenient because you could just stick them into an open flame to quickly sterilize them between plates. I am going to have to do this in co-op later this year!
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Mackfam
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MaryM wrote:
| Jen, I never knew you were such a bacteriaphile - who would have guessed.... |
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I don't know HOW you picked up on that? I'll have to be sure to remember this for one of those, "tell me 7 random things about yourself" memes that occasionally cruise around the internet. Hi, I'm Jen. I like tape, labels, post its, baskets, playing in the dirt, and culturing bacteria.
AtHomeScience wrote:
| It brought me back to my medical technologist days! |
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I didn't know you were a med tech! My mom was a med tech so it holds such a special little place in my heart!
Donna Marie wrote:
| Jen! How do you learn SO much about all of this? |
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I LOVE science!!! It's true! I probably got my love of science from both my parents, who both really enjoy the sciences! As I mentioned, mom was a med tech and my dad is a microbiologist/immunologist who has always done medical research and taught med students/now teaches nursing students (at Aquinas College in Nashville ). So, I essentially grew up in a lab. When other kids were playing with Barbie I was washing beakers, sorting magnetic spinners, brushing Barbie's hair in the fume hood, and cleaning her with alcohol and Kimwipes. While I certainly had the benefit of growing up with labs, lab equipment and a house that was imbued with scientific knowledge, it was my dad's ever-present sense of wonder and awe at God's creation that always inspired me. My dad's childlike sense of wonder: probably one of the most formational influences in my childhood!
Donna Marie wrote:
| Where do you find your focus for science?? |
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I'm not sure what you mean by focus, Donna Marie. But if you need help with direction: what to do, how to do it, where to get the stuff....I really, really recommend Home Science Tools. I reviewed the enormous resources (many free) they offer here. Hope that's what you meant.
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OHmomof2
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Not to gross anyone out, but...my dd just did this experiment about a month ago. The two "places" that had the most (colorful and amount) bacteria growth were a library book and the bottom of a shoe.
Blessings,
Pam
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MaryM
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OHmomof2 wrote:
Not to gross anyone out, but...my dd just did this experiment about a month ago. The two "places" that had the most (colorful and amount) bacteria growth were a library book and the bottom of a shoe.
Blessings,
Pam
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Thank you, Pam. Just what I wanted to hear - someone who has done it recently and had success!
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MaryM
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Mackfam wrote:
Take pics and let us know how it turns out! Or am I the only person that would be thrilled to see colonies of bacteria growing?????? |
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Hoping to thrill you this afternoon...
From earlier this week, this was dd's - source of swab for growth - the doorknob of the classroom at our co-op site. That one and the drinking fountain someone did had the most. Now no one is drinking from the drinking fountain . Those who did body swabs (mouth, nose, hands) did not have as much bacteria.
I don't have pics of the ones with the antibacterial disks but the worst inhibitor was hand sanitizer - did not seem to work at all...
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Mackfam
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Oh, I love it!!! I'm so glad you had good growth! 
MaryM wrote:
| I don't have pics of the ones with the antibacterial disks but the worst inhibitor was hand sanitizer - did not seem to work at all... |
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I know. Eye opening, isn't it?!
What fun!!!!!! Nothing makes me happier than a little snapshot of bacteria before I head off to pour myself a nice red while I make the lasagna!
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Jen Mackintosh
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Betsy
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I am totally thrilled!
I remember doing this in High School Biology class. So much fun!!!!!!!
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AtHomeScience
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Great plate picture? Did you try looking at the bacteria under a microscope?
I just happened to catch on Beakman's World that he made agar from gelatin and sugar that he poured into a narrow-mouthed jar lying on its side. So I did a quick Internet search: Homemade Petri Dishes jars can be sterilized in the dish washer.
Lots of related articles on eHow!
If you don't have sterile petri dishes, and you do have a pressure cooker, you could sterilize aluminum foil lined custard dishes filled with the homemade agar. See here.
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4Real Forums : Exploring God's Creation in Nature and Science
Topic: Where is the best bacteria?
