mcfarland standard and spectrophotometry give you a rough estimate of the concentration (as they use optical measures, they do not exclude dead cells debris - which depending on what your sample is, it may account for most of its content). Are you working with an easy-to-cultivate microorganism? I'm not sure what you want to do, but I believe a serial dilution followed by a spread plate would probably be the easiest way to give you a close estimation of CFU/mL.

Here, there is an easy explanation: http://www2.hendrix.edu/biology/CellWeb/Techniques/microspread.html

Find Mcfarland standard that may help you to calculate the conc. of CFU

Calculation of cfu/ml ..can be done by spectrophotometry

Preparation of cfu/ml can be done easily by Mcfarland Standard

mcfarland standard and spectrophotometry give you a rough estimate of the concentration (as they use optical measures, they do not exclude dead cells debris - which depending on what your sample is, it may account for most of its content). Are you working with an easy-to-cultivate microorganism? I'm not sure what you want to do, but I believe a serial dilution followed by a spread plate would probably be the easiest way to give you a close estimation of CFU/mL.

Here, there is an easy explanation: http://www2.hendrix.edu/biology/CellWeb/Techniques/microspread.html

serial dilution of culture and finally plating on agar plate can also give good reproducible cfu/mL count. This can be used in alternative to spectrophotometer and Mcfarland standard....its very simple..if you need more help plz feel free to ask ..

Good Luck :)

If you are dealing with a pure culture and would like to standardize the concentration in cfu/mL it would be important to standardize the hours of incubation (18h) using standard loop (1mm). Take 1mm loop and transfer to a fresh broth then do serial dilution and plate. If you can compare your sample with different dilutions of mcFarland, the better.

http://microbesunlimited,blogspot.com

1- Please find suitable medium for growth of your bacterium. LB agar or BHI agar are common media for growth of heterotrophic bacteria. But, if you want to need to produce high amount of biomass, you have to the growth requirements of your bacterium, carefully and select appropriate medium.

2- Now, you can use pour plate method or spread plate method for measuring the biomass as CFU/ml. This methods re common in the literature and I am sure you can find the method, easily in the texts and web.

3- It is better to use same media in biomass preparation and measuring the CFU sections. only difference is adding agar at later stage.

I really do not understand your problem: the number says how many colony forming cells you have in a ml. So if you plate a µl, you count the colonies, multiply that number with the dilution factor (here you used a 1000th of a ml) and you have it. for example if you find 43 colonies on the plate where you plated 1 µl, you have a titre of 4,3x10´`4 as cfu is always given as a number with one digit before the comma. Was this really your question?......

Do one thing, serially dilute the given sample either in sterile saline solution or in Ringer's solution and spread certain dilutions (0.1 ml) on agar medium plates. Count the number of colonies, it will be per 0.1ml, multiply it by 10 which will give you CFU/ml. Finally multiply it by the dilution factor, which will give you CFU/ml in the parent suspension.

Make serial dilutions and do pouring then place those test tubes at 40C, after growth determine CFU if your required CFU is found you can use specific test tube for your purpose or make slight changes accordingly..

What  optical density reading at 600nm can be equated to 0.5 McFarland standard  

Please I need help. when an author in a paper says that the number of bacteria is 7.1 of log (cfu) how can i calculate the real number of bacteria?

Dear Raman

Here you can have more explanation : http://technologyinscience.blogspot.com/2011/11/cfu-colony-forming-unit-calculation.html#.Wi62lNjI7IU

No idea pls