Bacteria Science Fair Questions - A few basic and complex questions about bacteria (Nov/04/2005 )
My teacher suggested that I did a little more scientific-based experiment, the topic on osmosis in bacteria, watching how they swell and shrink when in different agars. The site in which the site is at is https://www2.carolina.com/webapp/wcs/stores...6%7C1737%7C1744 , I'm not sure whether to pursue my first experiment or to continue on with this new onw. I'm more knowledgeable of the antibacterial/disinfectant experiment, but this new one sounds more interesting and fun, and perhaps more in depth with bacteria. I knwo that osmosis has to do with molecules going in and out of a bacteria's(in this case) pores in its membrane, but I'm no proffessor in the subject. If any one could give me advice or knowledge on osmosis.
the bacteria that will be used is food spoilage bacteria:
Bacillus cereus Plate Culture
Penicillium chrysogenum Plate Culture
Pseudomonas fluorescens Plate Culture
Saccharomyces cerevisiae Plate Culture
Serratia marcescens Plate Culture
and the agars are:
Control Agar
Sucrose Agar (0.5%)
Sucrose Agar (30%)
Sucrose Agar (60%)
Sodium Chloride Agar (0.5%)
Sodium Chloride Agar (15%)
Sodium Chloride Agar (30%)
Will this experiment be fine? (Kit at https://www2.carolina.com/webapp/wcs/stores...96%7C17377C1744 ) Thanks for your advice!
I have only read part of the posts but would just like to say that this statement and other like this in this topic is not true, im not having a go at you Homebrew as most of the advice you have given is well thought out. All bacterial strains should be considered as potentially harmful regardless of where you get them from and should only be use in a laboratory environment and disposed of correctly, if handled in the correct way they are perfectly safe to use but you should not assume that as you have bought it you can handle it any way you please.
Sorry that’s my rant over now, I’m a Microbiologist and I wouldn’t let any of my staff work in the laboratory without taking proper precautions. If you treat it as potentially harmful it is best practice as well as safe for yourself.
If you need any help or advice setting up an experiment let me know and I’ll help if I can. 
No problem, Redwalar -- I actually agree with you. But, that said, it would take a pretty big screw up for him to be shipped some pathogenic E. coli by mistake, especially from a company that very likely doesn't even have any pathogenic strains. I agree it's theoretically possible for such an event to occur, and thus agree that all bacterial cultures should be handled as if they were potentially pathogenic, but the real world chance of this occurring is pretty slim...
Thanks HomeBrew im glad you agree with me, I didn’t want to get off on the wrong foot seeing as I’m new here.
Yes I’d agree with you as well, if you treat all the cultures as potentially harmful and handle them in the correct safe manner you are also potentially avoiding cross contamination. I am used to handling wild type cultures of unknown origin and so tend to treat everything with a lot of caution.
The kit at https://www2.carolina.com/webapp/wcs/stores...6%7C1737%7C1744 , Does anyone think it would work for me to watch and observe the cultures under a microscope and record their (individual bacterium)length in microns(millionth of a meter)? The length would vary because of osmotic pressure. If I could, I would most likely measure 25 bacterium in each Petri dish to get an average, and their are 30 Petri dishes, so I'd measure 750 individual bacterium total. What do you think of this? Will it work? Thanks
How will you prepare your slides for the microscope? Do you have a micrometer eyepiece and slide (see here)?
I'm sure Bowdoin College does, and the advisor that's willing to help me will help me with that, but Redwallar said that it would be hard to catch the length of a bacterium in the sucrose agar before it swelled too much and popped, do you think I could just measure ones close to popping?
You may not be able to get any in the 60% sucrose agar, but as I said to you before this kit is designed to show why high concentrations of sucrose and saline are used as preservatives of food, at the high concentrations the bacterium will be killed off and only inhibited at the lower levels. You may want to have a look and see if its possible to do what you want it to do as its not designed for this, its just my opinion but this kit is trying to show the macroscopic effects of food preservatives hence the no experience required, to show the microscopic effects you will need to adapt or come up with a completely new experiment and have an experienced helper to guide you.