Mini-Organisms

[Sciencehelp]

Can someone assist me with a hypothesis regarding the effect preservatives on bacterial growth? the test consisted of vinegar+water, salt+ water, chicken bouillon cube+water, and tried vinegar+water+bouillion just to manipulate the effects to see what happens. The bouillion cube+water resulted with bacteria, salt water was cloudy and the vinegar was very clear. Can someone please explain this to me. I'm not a very good science student at all.
Thanks

[donnahardy2]

Dear parent,

I'm not sure what your hypothesis should be, but here is an explanation of the results.

Bacteria require a source of carbon and nitrogen in an aqueous(water) environment, as well as an optimum pH, salt concentration, and temperature to grow. In this experiment, the bouillon cube provided carbon, nitrogen, and salt at a particular pH (probably neutral or slightly acidic), and the vinegar is a potential carbon source and has a pH of about 3.5 to 4, depending on the concentration. Salt water would not contain a significant carbon or nitrogen source and the pH would be slightly acidic.

From the results, it sounds like the bacteria grew in the samples with the bouillon cube, so were probably supported by the extra carbon and nitrogen in the growth medium. The salt water and vinegar samples were missing the extra carbon and nitrogen, so bacteria were slower to grow. In addition, the vinegar has a low pH and this inhibits the growth of many microorganisms. I don't know what concentration of salt you used, but many bacteria are inhibited by high salt concentrations. Do you think the salt sample was cloudy because of bacterial growth, or because of undissolved salt?


Generally in a science fair project you want to have an experiment where results can be measured. Your hypothesis should be your guess of what the results will be based on background research. Do you need to help your child write up these results to turn in? If so, we can give you some more suggestions. However, if there were time to repeat the experiment, perhaps it would be good to redesign the experiment slightly and do it over again. If this is a possibility, let me know what grade your student is in.

Donna Hardy

[Sciencehelp]

I need help to write up the results for this project so she can fully understand what has taken place. Can you provide assistance.
Thank you[/code]

[donnahardy2]

Hi Parent,

I think we can help. But first, what grade is your daughter in? How did you tell if bacteria grew in the sample? Did you add bacteria from a known source, or did you wait for the samples to turn cloudy? How long did you incubate the sample? What was the salt and vinegar concentration?

Donna Hardy

[Sciencehelp]

my daughter is in the 6th grade, i waited for the bacteria to form until it got cloudy from the source, i waited for 2.5 days. 1 spoon of salt 250 ml of water to each solution. Can a graph be created for this project as well. This is my last straw my deadline is at 4:30 today eastern time zone.

[donnahardy2]

Here are my suggestions:

Make a bar graph with each solution on the x (horizontal axis). You will have 4 bars (one for each solution). On the y (vertical axis), put time. The range for the y axis will be 0 to 3 days. Mark the bar graph at the time the solutions turned cloudy. The vinegar solution remained clear, so it will remain at zero.

This will give you a graph that will satisfy the requirements of the project.


Donna Hardy

[cutie_gabby]

thanks for your help. do you know what the colors stand for? i really need help on this project and how to do it can you please get back to me with advice. i would really appreciate it. and can you tell me where to get the iodine and starch here in fresno ca? thank you.

[cutie_gabby]

thank you for the advice and uuuum... well what info should i use for my review of literature?????? Can you explain more to me about what iodine has in it to make the vitamin c or the juice change colors. thank you