Dear Clare, firstly you should plot OD600 nm vs time graph for your bacteria. Then in log phase of growth the slope of linear part can be calculated. The details were described by Friedrich Widdel in the attached file.

Best regards.

Dear Clare, firstly you should plot OD600 nm vs time graph for your bacteria. Then in log phase of growth the slope of linear part can be calculated. The details were described by Friedrich Widdel in the attached file.

Best regards.

Prepare the curve with time in hours and optical density at 600nm

Hi 

The optical method for count bacteria is  not accurate because it calculated the living and dead cells.

You can used total count of bacteria in solid media ache hour.

This is method used in generation time of microbial.

3/16/17

Dear Clare,

The information and attachment provided by Dr. Sudagidan are very good and should work for you.  I have attached another file that you can also use. It came from a microbiology lab procedure for calculating microbial growth rates + generation times. 

I hope this information helps you. If you have other questions, feel free to contact me at your convenience.

Bill Colonna, Center for Crops Utilization Research, Iowa State University, Ames, IA, USA   [email protected]

Obtain the growth curve of the bacterium under study and draw the time on horizontal column and CFU/ mL on vertical column and look to the linear part and obtain the generation time by Frederich Fiddel equation and calculate growth rate mathematically

Measuring OD600 at regular intervals (eg. every hour) is the most common and easiest way of monitoring bacterial growth. There will be very few dead cells until stationary phase is reached so it is not necessary to determine the actual cell count (this has its own drawbacks eg. agregated cells growing as a single colony leading to underestimates). As the OD of the culture increases you will need to dilute culture samples before measuring the OD as the relationship between cell number and OD is only linear over a certain range (the document provided by Mert suggests up to 0.4). Plot time (h) against LnOD600 which should give a straight line for the exponential phase from which you can calculate the specific growth rate (slope of line) and doubling time. One important point when comparing different strains - make sure culture conditions are identiclal i.e. same batch and volume of medium, same size culture vessel, same incubator/shaking etc.

Mert Sudagidan, PANKAJ BHATT, Alaa Kareem Niamah, W.J. Colonna, Gamal Enan and Mark D Farrar.

Thank you for your help.

Have a good day!!

Clare, OD600 does not scale linearly with cell density, so you will need to either calibrate (plot OD600 vs cell/CFU number) for every strain you use, or do a colony counting assay/count cells directly with a hemacytometer or other method.

OD600 can be influenced by factors such as cell shape and cell arrangement that do not reflect changes in cell number, so I would not rely solely on measuring optical density.

Goodluck

https://github.com/ashrafashhab/Bacterial-Growth-Curve-Plot-OD-Vs-Time-h-