How to Perform Serial Dilutions in Microbiology 

Gloves are dangerious if you use a burner for sterile conditions.

plates that have the number of colonies within 30-300 based on what I've learned... more than 300 is too numerous too count while less than 30 is too few to count

Thank you for your comment! Aseptically removing the cap and holding in your hand is one technique to minimize contamination during a serial dilution alongside inversion on the bench. If inverting onto a bench, make sure this is sterile or perform the dilution series in a biosafety cabinet or laminar flow hood.

There are many resources online that can help you determine the correct amount of powdered sample to add to create a stock solution. In general, a stock solution is made by weighing out an amount of the solid (powder) and dissolving it in an amount of solvent to get the desired concentration, or Molarity, of the stock solution. Dissolving 1gm of powdered sample into 10ml of water would yield a 1:10 dilution of the powdered sample.

Do it 4 times. Don't thank me.

Really i need the answer!,,

We used 9.0 mL tubes of 7.2 pH Phosphate Buffer

This is up to the SOP guidelines you follow. At our facility, we do not use a hood when performing dilutions.

Sarah - To know how much to dilute your sample in order to get a reasonable number of colonies to count, you must know what your CFU concentration is to begin with and what you want to end up with. If you are using Microbiologics products, it is easy to know what your original CFU concentration is because we tell you. For example, Microbiologics Epower™ E3 product is equal to 1,000 to 9,9999 CFU per pellet. If you are not using a quantitative product, you will need to make a suspension of the microorganisms, measure the concentration using a spectrophotometer or turbidimeter, and then dilute the suspension until you get within countable range. To calculate the CFU concentration of your original sample, you will need to work backwards. Count the number of colonies on your plate and then multiply this number times the dilution factor. Check out the Microbiologics Dilutions Guide to learn more: www.microbiologics.com/Microbiologics-Dilutions-Guide

@@Microbiologics thank you very much!

You cannot reuse them, they're no longer sterile. They must be thrown out properly

Yhaa

That is the bacteria in dried up form. In this form they can be kept for a long time and they came alive when placed in the buffer

Incinerator.

If using a 1.0 mL inoculum size, we suggest dividing the inoculum onto several agar plates.

Each dilution is plated on the video as a teaching tool so the viewers will understand what the recovery will be for each dilution. If you do not feel that plating each dilution is necessary, you can adjust your procedure accordingly.

After spreading the inoculum on the surface of the agar plate, make sure it has been absorbed into the agar before inverting the agar plates during incubation. The length of time this will take depends on the volume used to inoculate the plate and the depth of the agar. Visually check the agar prior to inverting the plate. If the inoculum has not absorbed into the agar, it can drip onto the lid of the Petridish while inverted.

Inverting the plate prevents condensation kn the lid and dripping water on the colonies

@@Microbiologics ❤

yeah you can..but...the reason you dilute 1ml into 9ml to get a total of 10ml is for simple mathematics calculation...your case would be an mathematic nuisance.

Maybe 37°C because E.Coli can be found in human body and doing just fine

You can do that. It is just important to make sure that you are measuring your small sample volume accurately. As the volume of a measurement decreases (1 µl vs. 1 ml), accuracy of the measurement also decreases. So if you need to dilute from 10^7 to 10^2, you either need to do serial dilutions, or you need to work with a large enough volume to ensure that the dilution is as accurate as possible.

hi, on my view the reason we do serial dilution its because we need to know the amount of bacteria present in the original sample by decreasing their volume

Its a standrad process for dilution gives accurate measurment.Here we add a small sample to a measured volume of the dilution solution. We can't think like mixing a smal drop in an unknown quantity of the dilution solution.

Calculating the concentration of your stock solution will depend on how you manipulated the stock solution to get a readable plate. For example, if you removed 1ml from your stock solution, plated it, and counted 10 CFU on this plate, your concentration would be 10 CFU/ml. If you removed 1ml of stock solution, diluted 1:10, plated 1ml, and counted 10 CFU, then you would need to factor in the dilution for your calculation. If you have specific questions based on your protocol, please feel free to reach out to our Technical Support Team at techsupport@microbioloigcs.com.

Technically, 10 colonies is too low to use for CFU/mL. The standard is to use a plate with 30-300 colonies.

It is not advisable to determine an average from plates prepared from 2 different dilutions unless both are in your designated ‘countable’ range. This is because counting plates with high counts can lead to inaccuracy. (It is widely accepted that the range for countable colonies on a standard agar plate is between 25 and 250 for most bacteria). However if both are in your countable range, you would perform the calculation and then determine the mean. For example: If the 10^5 plate count was 240 CFU, the final count, after multiplying by 100,000 (or 10^5), would be 24,000,000 CFU/ML If the 10^6 plate count was 28 CFU, the final count, after multiplying by 1,000,000 (or 10^6), would be 28,000,000 CFU/ML The average of these 2 is 26,000,000 CFU/ML (or 2.6 X 10^7)

We used E. coli for this demonstration: www.microbiologics.com/0483E7

okay ,thank you can you show me how isolate xanthomonas vesicatoria from tomato plant properly?

and what does it mean by 5x10 to pwr 6?

5x10 to the pwr 6 is 5x10^6 or 5,000,000 colony forming units (CFU).

If I get 35 colonies on serial dilution of 10^-6 then how I ll write it??

John Simple your welcome

Yeah, use a flow hood lol

I think the producers are aware of this fact, but recording is more easy this way.

Because concentration of sample is different in every test tube.

You have whats app

You have wats app

Same 😭

May God bless you 🙏