Impact of growth medium components on absorbance-viable cell count correlation and cell surface area of Cereibacter sphaeroides O.U.001

Today different methods are used in microbiology laboratories to monitor the growth and development of bacteria. Optical density measurement is one of the most preferred methods as being fast, practical and low cost. On the other hand, it cannot differentiate between living and non-living cells in the culture. Moreover, alteration in cell size may lead to the variations in the measurements. As a result, optical density measurements alone may cause wrong experimental results. Therefore, it is necessary to determine the absorbance-living cell number relationship for each specific culture condition. In this study, Cereibacter sphaeroides O.U.001 was cultured under four different culture conditions regarding the type of carbon and nitrogen sources (Malate/Glutamate, Molasses/Glutamate, Malate/N2 and Acetate/Glutamate) and the effect of medium composition on cell size and absorbance-viable cell count relationship was investigated. Equations were obtained from curves drawn as optical density (x-axis) against CFU/mL (y-axis). Field emission scanning electron microscope was used to observe the effects of medium compositions on the size of Cereibacter sphaeroides O.U.001. It was revealed that the composition of the medium affected the absorbance-number of living cells relationship. Furthermore, it was evidenced that the size of the cells was changed significantly upon changing the medium composition. To conclude, it is advised that before performing experiments in which the cell numbers are significative, a comparative calibration curve for optical density measurement-the living cell number relationship should be established for more accurate results.