What is the purpose of using a spectrophotometer in a microbiology lab?

The purpose of using a spectrophotometer in a microbiology lab is to measure the turbidity of microbial cultures. Turbidity refers to the cloudiness or haziness of a liquid caused by the presence of suspended particles—in this case, microbial cells. By passing light through a sample and measuring the amount of light that is transmitted or scattered, a spectrophotometer provides a quantitative assessment of the turbidity, which correlates with the concentration of microorganisms in the culture. This is particularly useful for monitoring the growth phases of bacteria, as the turbidity increases as microbial populations expand.

Using this method allows researchers and laboratory technicians to track growth without having to count cells directly or remove samples from cultures, which could affect the viability of the organisms. Additionally, it aids in determining the best time for harvesting microorganisms or for conducting other tests.