Optimize Bacterial Growth Studies Using Permanent Shaking And Heating

Monitoring growth of prokaryotic cells and yeast is an important tool in life science as well as in the food industry. A well-established method to quantify bacteria and yeast cells is turbidometric measurement. This technique is based on the fact that the solution becomes increasingly turbid as the number of cells in a solution increases: light which passes through the sample is scattered by the micro-organisms, and the turbidity is proportional to the number of micro-organisms in the solution. This turbidity can easily be measured using a spectrophotometer. Cells contain numerous macromolecules that absorb light, for example DNA (260 nm), proteins (280 nm), cytochromes (400-500 nm), and cell pigments. When measuring bacteria and yeast by light scattering it is best to pick a wavelength where absorption is at a minimum and, for most cultures, 600 nm is recommended. At this wavelength the optical density (OD) of the sample is directly proportional to the number of cells present and can therefore be used as a method to follow cell growth.

Precise determination of cell number via 600 nm absorbance measurement is only possible by generating a respective standard curve (viable plate count or cell mass plotted as a function of OD).

The Infinite 200 PRO microplate reader series, along with other microplate readers from Tecan’s portfolio, has been successfully used for various studies analyzing bacterial and yeast growth (1-7).