How to do this experiment? - (Nov/18/2014 )
I am doing an experiment where I am testing home-cultured kefir vs. store-bought. I want to see which has more bacteria- I understand I can estimate by simply looking at it, but is there a more accurate way that does not require expensive equipment? How would I be able to more accurately tell which kefir has more bacteria? thank you.
The microbiological way to do this would be to plate out a range of dilutions made from suspensions of the kefir, and then count how many colonies grow on the plate... however, kefir is a mix of several different types of yeast and bacteria, which means that some might not grow in culture, or some might out-compete others, giving you inaccurate results.
There is no really easy way to count bacteria in suspension, but the best you could do is find a hemocytometer and attempt to use that
However, I suspect that you will find that there isn't much difference between the two types of kefir - in both situations, the bacteria and yeast will grow to use the available nutrient supply. What differences you might find are more likely to be down to the range of types of bacteria and yeast present in each.
well to count the bacteria- I could just take photos of each slide, then import it into ImageJ, which will count the bacteria in the photo. The part I am having trouble with is that kefir is mostly milk protein, what I mean is on the slide you mostly see the milk, and there are 'rivers' of the bacteria. this would make it very hard to get equal results. Is there a way to "dissolve" the milk protein, so its a bit more simple?
My advice would be to take some kefir and grind it as fine as you can, then count. Your images on ImageJ should work OK.
Another possibility would be to filter the milk, if a suitable filter is available, to remove solid matters.
The problem with photos is that you don't have a defined volume, but just an area (where you might need a size indicator too). A counting chamber has a defined distance between cover slip and chamber grids on the ground, so that you have a known volume.
And they're not that expensive, see here (though compared to a professional one these ones suck, but for home use might be sufficient).
hobglobin on Wed Nov 19 17:42:54 2014 said:
Another possibility would be to filter the milk, if a suitable filter is available, to remove solid matters.
The problem with photos is that you don't have a defined volume, but just an area (where you might need a size indicator too). A counting chamber has a defined distance between cover slip and chamber grids on the ground, so that you have a known volume.
And they're not that expensive, see here (though compared to a professional one these ones suck, but for home use might be sufficient).
Yes, that was the main problem- Getting a defined volume and area. How fine of a filter would I need to filter out the milk solids? would http://www.amazon.com/Whatman-1440-110-Quantitative-Circles-Diameter/dp/B007FXLCXY/ref=sr_1_2?s=industrial&ie=UTF8&qid=1416429259&sr=1-2&keywords=milk+filter work? Or could I use something cheaper such as a coffee filter? I don't see how a size indicator would really help, I could just use the same magnification which would mean the same viewing size.