What is a good way to measure the growth of bacteria?

Question

I don't have a huge amount of money and I have access to the equipment in a high school chemistry lab

Answer 1

From my experience in college microbiology we counted bacteria by doing serial dilution followed by plating, along with this we did uv absorbance tests on the serial diluted samples so that a popultion count vs uv abs curve could be made. This made future plating unnecessary.

The most accurate way is using serial dilution. That is you take a sample, say a 1 ml sample, place in a test tube that has 9 ml of water (isotonic ok), now the sample is 1/10 the original concentration, you do this several times, making a 1/100, 1/1000,
1/10,000, ect. Then you add 1/2 ml or so to a growth plate,
the idea is to get such a dilute solution that each colony that grows is considered to have come from a single microorganism.

If you see a lawn of growth appear rather than individual colonies that grow into a lawn then your dilution was not enough for that particular dilution.

So, when you see these individual colonies appear, you can back track on your dilutions to figure out the original concentration of bacteria.

Now, that is alot of work, but you can shortcut this in future procedures, those tubes that I mentioned above that were diluted,use a uv spectrophotometer to measure the absorption compared to your diluting fluid (I recommend sterile 0.9% NaCl)

Some of those readings will be off the chart (frequency 580nm from memory, look up max abs freq for DNA, that would be best I gguess, but 580nm seems to stick in my memory)

Anyway, when you get the data from your plate, you can compare that with the uv abs, and will be able to make a curve that will approximate the bacterial counts base on uv abs alone.

Answer 2

Do you have access to petri dishes and growth media? The viable plate count is the standar way to determine the number of bacteria in a culture. However, if you need several measurements over time to determine growth, it will be very labor intensive.

The viable plate count involves growing the culture overnight in broth. The next day, serial 10-fold dilutions are made in sterile saline (1:10 to 1:100,000,000). Then, 0.1ml from the 1:100,000,000 the 10,000,000 and 1:1,000,000 dilutions are plated onto separate petri dishes with sterile nutrient agar. The plates must be incubated overnight at 37 degrees centigrade or at room temp for 2-3 days. After bacteria have grown, then number of colonies are counted and multiplied by the final dilution factor to determine viable bacteria/mL.

Answer 3

take a sample at certain time intervals and dilute it in powers of 10. THen take a sample of that mixture and grow it on a petree dish.

Count the number of colonies formed and then backtrack the calculations to the original sample.

The technique is called Counting Bacteria by Dilution and Plating. Google it if you want exact procedures. You only need food for the bacteria to grow on.

Answer 4

decrease than is the link for a fast communication btw Johannes Rouska, , and Nalini M. Nadkarnib from Lund college in case you click on source decrease than you will discover each and every of the appropriate tables and formullas ;) solid success aDepartment of Microbial Ecology, Lund college, Ecology construction, Solvegatan 37, SE-223 sixty two Lund, Sweden bThe Evergreen State college, 2700 Evergreen freeway, Olympia, WA 98505, united states of america gained 24 November 2008; revised 25 January 2009; conventional 6 February 2009. accessible on line 26 February 2009.

Answer 5

My teacher once told me to try to count the amount of bacteria i could see with a microscope and then multiply it with the area of the petri dish or something like sorry i'm not very useful.

Answer 6

Area covered on a culture dish.

Answer 7

a petree dish