# Is the relation between OD reading and cell concentration (cells/mL) of bacteria different in various culture media?

For instance, assume that the cell concentration of S.pasteurii cultivated in an Ammonium YE medium is estimated by the expression 8.59* 10^7(Z^1.363) where Z is the reading at OD600. Now, if I cultivate the S.pasteurii in an Acetate YE medium, is it possible to use the same equation to estimate the number of cells according to the OD readings?

## Popular Answers

DeletedDefinitely, you cannot use your equation with both media. As of matter of facts, even you cannot use your equation using the same media if you change the conditions in which you obtained your equation. As you know, an equation is to predict the behavior of the microorganism under the conditions you selected and tested. Therefore, if only one of the parameters used to obtain the equation changes, then your equation is not valid anymore. At least you can demonstrate that the microorganism has the same pattern of growing even changing the conditions. In the case to change the media from ammonia + YE to Acetate +Ye, I am pretty sure that the light adsorption of the media (OD) will not change, but this is completely different history about the effect of acetate on the growing of the microorganism. Perhaps acetate stimulates or not the growing in which case you will have a different pattern of growing. Surely, this pattern will not fit in your equation, so that your equation is again not valid anymore. I think no choice you have to re-do your calibration curve OD vs Growing (CFU or DCW).

Diethelm Kleiner· University of Bayreuth## All Answers (119)

Azad Ismail Saheb· Kuwait Institute for Scientific ResearchIts best to have an equation for the defined growth conditions: Media, media constituents, pH, temp and time.

DeletedIn attachment OD is 0.7 from 5th to 10th hour but CFU decreases after 5th hour

DeletedRichard H Bentham· Hindmarsh Water Treatmentif you read back through the comments - you will see we agree on many things. Optical density is useful and reasonably accurate in the exponential growth phase when the numbers of dead cells is minimal - and so is a good measure of viability.

Hi everyone,

look at the already published literature that documents using 0.1 absorbance at 600nm of bacterial cultures in the exponential growth phase for calculating an approximate 10^6 cells per ml - confirmed by culture of the inoculum at commencement of the experiment.

Also look up the Beer-Lambert Law and molar extinction coefficients and it should all become very clear to you.

So long as the culture media does not have a major absorbance at 600nm then a culture blank will wipe out any problems re: absorbance of the bacterial culture.

cheers,

Richard

Richard H Bentham· Hindmarsh Water TreatmentDeletedI am agree with you Optical density is accurate in the exponential growth phase .

I have changed my comment.

Arieh Zaritsky· Ben-Gurion University of the Negev1. For the relationships between OD and cell mass/size and shape, learn the work of Arthur L Koch of the late 1960's - particularly the Biochem Biophys Acta;

2. For the relationships between cell size/mass and growth rate (reciprocal of doubling times), go through the brief article of Willie D Donachie in Nature, 1968.

* The decade 1958-1968 indeed opened up the field of Bacterial Physiology, by the leadership of Ole Maaloe and Charles Helmstetter.

** These studies (by M Schaechter, CH Helmstetter, WD Donachie and AL Koch) are seminal and crucial for understanding Bacterial Physiology! **

Renuka SubramaniamChinnashanmugam saravanan Kalki· Pondicherry UniversityMichael T Peglar· Northern Virginia Community College - Annandale CampusJacques GE Thierie· Free University of BrusselsChristopher Lee Fogarty· University of HelsinkiRasoul Shafiei· University of IsfahanIn addition, you should make a difference between culturability and viability.

Anshul Sharma· University College London(Look for thermo fisher , they have done an analysis regarding this on a bacterial culture and with different spectrophotometers)

Rasoul Shafiei· University of IsfahanI could not find it.

Anshul Sharma· University College LondonRasoul Shafiei· University of IsfahanZakaria Al-Qodah· Taibah University, Madina , Saudi ArabiaShailendra Dwivedi· All India Institute of Medical Sciences JodhpurCan you help by adding an answer?