Bacteria Science Fair Questions - A few basic and complex questions about bacteria (Nov/04/2005 )
For my freshman science fair project, my topic is: How effective are different antibacterials and disinfectants on bacteria. I will measure how effective they are by putting the antibacterial/disinfectant in the middle of the petri dish while the bacteria are growing, and see if they spread away from the centerpiece. The more effective the antibacterial/disinfectant is, the further the bacteria will back away. However, I have some questions. 1.) Does this have any glitches/major or minor problems? 2.) How should I go about staining, is Methylene Blue fine? 3.) is 1 oz of this stain enough for 15 full Petri dishes full of bacteria? 4.)My major question is, what bacteria should I use? I thought of E. coli, but the local public Health Center says it could become hazardous and dangerous. Which bacteria would be the best? I great list of pure types of bacteria I could get is at
http://www.enasco.com/Search.do?searchTerm...acteria+Culture . Please respond and give your advice, and tell me which bacteria would be the best for my project, bt please look into it, don't randomly guess! 
Thanks!
P.S. Will these MicroLIVE Bacteria Cultures work well? The ones sold at the website I listed above. Thanks! -crossbow1313@hotmail.com
hi
i looked into the site which u have given and i think E coli would be the best 4 ur project as it can b easily cultivated and there are many media 4 its growth,it can b easily differentiated 4m other bacteria(enterococcus) and it multiplies within 20 minutes.
staining:
why dont you do gram staining.i think that would be better than methylene blue,coz gram staining helps u differentiate gram positive bacteria from gram negative bacteria(as u r using E.coli which is also a gram negative bacteria).pick up 1 colony 4m each plate and do gram staining to confirm tat only gram negative org(may be E coli)has grown in ur plate and also c the morphology of the colonies in each plates if u find any difference do gram staining and find out whether they are gram positive or negative organisms.to confirm that u have got only E coli in ur plates u have to do biochemical test.
GUD LUCK
Any lab strain of E. coli is perfectly safe. That is not to say all strains of E. coli are safe -- don't play around with E. coli 0157:H7, for example, but any lab strain you can buy is quite safe.
Also, I'd just lke to point out that your statement "...while the bacteria are growing, and see if they spread away from the centerpiece. The more effective the antibacterial/disinfectant is, the further the bacteria will back away..." is incorrect.
The clear zone that appears around the chemical in question is due to the action of the chemical on the bacteria near it -- it either kills them (a bactericidal chemical) or stops them from growing (a bacteriostatic chemical). As the chemical on the plate diffuses out into the media, a concentration gradient is formed -- as the circle of diffussion gets wider, the concentration of chemical at the edge of the circle decreases. Thus, a very effective agent (one that is bactericidal or bacteriostatic at very low concentrations) will produce a larger circle of clearing than will one that only acts effectively at relatively higher concentraions.
Thanks for the advice that measuring the cleared zone won't work, but how then do you think I should measure effectiveness of different antibacterials/disinfectants on bacteria? Thanks - crossbow1313@hotmail.com
Also - The public lab said that swabbing my mouth would work instead of using E. Coli, what do you think? E. coli or mouth-swabbing? Mouth-swabbing would be easier, but there'd be no way to tell which type of bacteria it is, and there might be several different types. 
Also - The public lab said that swabbing my mouth would work instead of using E. Coli, what do you think? E. coli or mouth-swabbing? Mouth-swabbing would be easier, but there'd be no way to tell which type of bacteria it is, and there might be several different types.
I didn't say measuring the cleared zone won't work -- it will -- I was just saying that your understanding of how the zone came about was incorrect.
I don't think that swabbing your mouth will work as well as a lawn of pure bacteria, because it will be a mixed population (as you noted) and if some of the bacteria are resistant to (not affected by) the chemical, they will grow right up to the edge and there will be no zone to measure.
It's the difference between asking "Does this chemical kill or stop the growth of E. coli?" and asking "Does this chemical kill or stop the growth of all bacteria in my mouth?".
another possible source of free and harmless bacteria is your local university, if you have one close by?
my U had a teaching lab full of bugs; the e coli was bona fide and would react in predictable ways during testing, but not likely to hurt you unless you ate a bunch of it
homebrew's totally right, your mouth bugs are not such a great experiment because of all the unknowns. a good experiment keeps all things the same, except one variable...in your case, the disinfectant...or otherwise any data you generate is meaningless, although the plates might grow up some good icky stuff
Yes, I haved contacted the local University, but they have no bacteria I could use. Do you think the MicroLIVE Bacteria Cultures will work? There is E. coli and other bacteria cultures at http://www.enasco.com/Search.do?searchTerm...acteria+Culture , but I'm not sure if they'll work, haave you heard of them before? Thanks again -- crossbow1313@hotmail.com
I would also like to suggest, once you get the bugs in, don't start them until you are prepared to propagate the cultures until you are done...do you have a 37OC incubator to grow them in? I'm guessing you have access in your science labs? there should be instructions on propagation and the appropriate ways to store cultures so they don't die on you
I don't know about the laws in your state, but you may want to have your teacher/mentor do the actual ordering? Can you order them yourself without getting in trouble?
No, I think someone else will have to do the ordering, but I have some questions to your response. I'm new to growing bacteria, and so I don't know some of the obvious terms most people might know. For example, what is propagation? Sorry to ask, but also when you say 370C incubator, do you mean heating an incubator to 370 degrees Celsius or is that a model number? Thanks, and also, when I grow my bacteria, do you think a standard incubator will have room to fit 15-20 Petri dishes in it at once, and for 2-4 days?
The MicroLIVE Bacteria kit from eNasco will work fine. The bacteria should be grown on L-agar plates at 37°C (98.6°F).
Are you being supported by a science teacher? Do you have any equipment available to you at all?
Are you being supported by a science teacher? Do you have any equipment available to you at all?
Is an L-Agar plate just a normal sized petri dish with agar? And also, the equipment I have available to me is an incubator, petri dishes, agar, I can order the bacteria, and other basic things such as gloves, goggles, etc., but I don't have access to an autoclave, so will sterilizing the materials in boiling water for about 5-10 minutes work? Also, what other materials do I need that you know of? Thanks -- crossbow1313@hotmail.com