What is a spectrophotometer primarily used for in microbiology?

A spectrophotometer is primarily used in microbiology to assess the turbidity of bacterial cultures. Turbidity refers to the cloudiness or haziness of a solution caused by the presence of microorganisms, and by measuring the amount of light that passes through a sample, a spectrophotometer can determine how many cells are present in a culture. This measurement is often expressed in terms of optical density (OD), which is proportional to the concentration of microbial cells in the sample; higher turbidity corresponds to a higher concentration of bacteria.

Using this technique, researchers can monitor the growth rate of bacteria indirectly, as changes in turbidity reflect alterations in cell populations over time. This makes it a valuable tool in determining the growth phase of cultures and quantifying bacterial load without the need for plating techniques. Spectrophotometry is not suitable for identifying specific bacterial species or estimating pH, as it primarily provides data on the concentration of particles in suspension rather than specific biochemical properties or identities.