E. coli growth curve measurement experiment

Summary

A certain amount of microorganisms, inoculated in a suitable fresh liquid medium, cultured at a suitable temperature, the logarithm of the number of bacteria as the vertical coordinate, the growth time as the horizontal coordinate, the curve made is called the growth curve. Generally, it can be divided into four periods: delayed period, logarithmic period, stabilization period and decay period. Different microorganisms have different growth curves, and the same microorganisms have different growth curves under different culture conditions.

Operation method

Growth Curve Measurement

Principle

There are many methods to determine the growth curve of microorganisms, including hemocyte counting method, plate colony counting method, weighing method, turbidimetric method and so on. This experiment uses the turbidimetric method, because the concentration of the bacterial suspension and turbidity is proportional to the concentration of the bacterial suspension, so you can use the photoelectric colorimeter to determine the optical density of the bacterial suspension to infer the concentration of the bacterial solution, and the measured optical density value (OD value) and its corresponding culture time graph, you can draw the growth curve of the bacteria under certain conditions. Now there is a direct test tube can be measured OD value of the photoelectric colorimeter, as long as the inoculation of a test tube, regularly measured with it, you can make the growth curve of the bacteria.

Materials and Instruments

Escherichia coli
Peptone meat paste
Test tubes Spectrophotometer Self-contained water bath oscillator Shaking table Sterile pipettes

Move

1. NumberingEleven large test tubes containing meat paste peptone liquid medium were taken and marked with a marker pen to indicate the time of incubation, i.e., 0, 1.5, 3, 4, 6, 8, 10, 12, 14, 16 and 20 hours.
2. VaccinationUsing a 1 ml sterile pipette, accurately aspirate 0.2 ml of E. coli culture solution at a time and inoculate into each of the 11 numbered large test tubes of meat paste peptone liquid medium, shaking after inoculation to mix the bacteria.
3. CultivationThe 11 test tubes after inoculation were placed on a self-controlled water bath shaker or shaker at 37°C for oscillation incubation. At 0, 1.5, 3, 4, 6, 8, 10, 12, 14, 16, 20 hours respectively, the test tubes numbered for the corresponding time were taken out and immediately put in the refrigerator for storage, and the optical density value was determined turbidly in the last year.
4. TurbidimetryUsing uninoculated meat paste peptone medium as a blank control, the photoelectric turbidimetric assay was carried out at 540~560 nm wavelength. Starting from the sparsest concentration of bacterial suspension in order to determine the concentration of large bacterial suspension with uninoculated paste peptone liquid medium diluted appropriately, so that its optical density value within 0.1 ~ 0.65, OD value records, pay attention to multiply the times of dilution.5. ResultsThe measured OD values were filled in the table below.

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