Turbidity estimates the number of viable cells in a clear liquid media or broth.

Turbidity is a measure of the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. In microbiology, turbidity is used as a simple and quick way to estimate the growth of bacteria in a liquid culture.

Here are the steps to estimate the number of viable cells in a clear liquid media or broth using turbidity:

1. Prepare the Sample: First, you need to have a bacterial culture in a clear liquid media or broth. The bacteria should be in the exponential phase of growth, which is when the bacteria are growing and dividing at the fastest rate.

2. Calibrate the Spectrophotometer: Before you can measure the turbidity, you need to calibrate the spectrophotometer with a blank sample. This is usually the media or broth without any bacteria.

3. Measure the Turbidity: After calibration, you can measure the turbidity of your bacterial culture. This is done by placing the culture in a cuvette and inserting it into the spectrophotometer. The machine will pass light through the sample and measure the amount of light that is scattered. The more light scattered, the more turbid the sample is.

4. Estimate the Number of Viable Cells: The turbidity of the sample is directly proportional to the number of bacteria in the sample. Therefore, you can estimate the number of viable cells by comparing the turbidity of your sample to a standard curve. The standard curve is a graph that relates the turbidity of a sample to the known number of bacteria.

Remember, this method gives an estimate of the number of viable cells. To get an exact count, you would need to use a method like plate counting.