# How do you calculate bacterial growth rate from OD?

## How do you calculate bacterial growth rate from OD?

Assuming that OD is directly proportional to the number of cells (it not always is), the simplest procedure is to grow the culture and take OD measurements at fixed intervals, then plot the growth with lnOD as the y-axis and time in the x-axis to find what part of the curve is linear and then calculate growth rate from …

How do you calculate the number of bacteria in a culture?

Calculate the number of bacteria (CFU) per milliliter or gram of sample by dividing the number of colonies by the dilution factor multiplied by the amount of specimen added to liquefied agar.

What is the formula for calculating bacterial growth?

The rate of exponential growth of a bacterial culture is expressed as generation time, also the doubling time of the bacterial population. Generation time (G) is defined as the time (t) per generation (n = number of generations). Hence, G=t/n is the equation from which calculations of generation time (below) derive.

### How do you measure bacterial cell concentration in a liquid culture?

Key Points

1. Directly counting blood cells or tissue cells by using a hemocytometer can determine the concentration of a known volume.
2. Counting the number of colonies that arise on a pour plate can calculate the concentration by multiplying the count by the volume spread on the pour plate.

How do you measure OD600?

How is OD600 measured? OD600 is typically measured using a bench-top spectrophotometer, but can also be measured using our Photopette handheld spectrophotometer. A sample is placed within a cell or cuvette, and a light source of 600 nm is directed towards the sample.

Why do we use 600 nm to measure cell concentration?

Optical density measures the degree of light scattering caused by the bacteria within a culture; the more bacteria there are, the more the light is scattered. The 600-nm wavelength is specifically chosen for bacterial OD measurements because unlike UV wavelengths, 600 nm is not harmful to the culture.

#### How do you calculate E coli concentration?

For E. coli cell cultures, OD600 of 1.0 = 8 x 108cells/ml. E. coli concentration can be calculated by multiply OD600 readings with 8 x 108.

How do I calculate average growth rate?

Write out the formula The formula used for the average growth rate over time method is to divide the present value by the past value, multiply to the 1/N power and then subtract one. “N” in this formula represents the number of years.

How do you calculate OD from cell concentration?

You can estimate that an OD600 of 1 corresponds to approximately 8 x 108E. coli cells per ml. Mathematically, an OD of 2 would correspond to 2 x (8 x 108) cells/ml = 1.6 x 109 cells/ml. That is assuming that the OD is directly proportional to the number of cells over that range of OD.