Measuring Bacterial Growth with Spectrophotometers

The ability to measure bacterial cell growth is an important tool in the biological sciences tool kit. Spectrophotometers are a great piece of equipment for performing these bacterial cell growth measurements in your lab. Spectrophotometers or microplate readers with temperature control allow you to process large numbers of samples efficiently and document the effects of different influential factors such as growth environments, growth inhibitions, growth promoters, etc.

In industrial and microbiology labs optical density (OD) measurements have become the preferred and standard approach for measuring bacterial growth. This is due to its speed and simplicity. An OD measurement characterizes the amount of light that is lost due to scattering and absorption at a given wavelength, e.g. 600 nm. 600 nm is the most frequently used wavelength in bacterial growth measurements, resulting in the commonplace nomenclature “OD600”.

A prime example would be using a spectrophotometer to monitor the growth of the bacteria E. coli and its inhibition by ethanol at a variety of wavelengths in cuvettes or microplates. The ability to transfer plasmids into E. coli enables production of recombinant proteins. Endpoint quantitation of E. coli is used to normalize results to a standard number of bacteria and inhibitory effects can be studied via growth studies. Absorbance at 600 nm is the recommended wavelength for measuring solutions containing E. coli or other bacterial samples.

There is an enormous amount of research citing the use of microplate readers to measure bacterial cell growth at 600 nm e.g. studying post antibiotic effects, detecting sublethal concentrations of antibacterial agents and examining the metal-ion tolerance of various strains of E. coli. Much of this research notes that while a variety of absorbance readers can read bacterial endpoint and growth curves at 600 nm, maintaining a uniform temperature of 37 degrees Celsius is recommended for reading the changing absorbance of the growth of E. coli over long periods of time, thus eliminating variations due to environmental temperature changes.

If you are looking to measure bacterial growth in your lab, the Benchmark Accuris SmartReader 96 Plate Reader is an excellent spectrophotometer choice from the Benchmark Accuris range. Available now at