What Is a Bacterial Culture?

Bacterial growth curve refers to single-celled microorganisms. It inoculates a small amount of single-cell microorganisms to a certain volume of liquid culture medium, and then cultivates them under appropriate conditions. Samples are taken regularly to determine the number of cells. Use the logarithm of the cell growth number as the ordinate and the culture time as the abscissa, and draw a curve as shown in the figure. We call this curve the bacterial growth curve. ^[1]

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Bacterial growth curve determination principle

Bacteria were inoculated into the culture medium in an Erlenmeyer flask with a test tube with a side wall, and the Erlenmeyer flask was taken out regularly at a suitable culture temperature and good ventilation, and the bacteria concentration (optical density) was measured with a "721" spectrophotometer. Value, OD value), and plot the obtained result with the corresponding culture time to obtain the growth curve of the bacteria. The advantage of this assay is that the OD value is continuously read under the normal growth conditions of the same culture container without changing the volume of the bacterial solution, so not only can the bacterial growth curve be measured, but also the same strain can be compared in different media and culture conditions. Growth pattern. ^[2]

Bacterial growth curve measurement steps

(1) Bacterial liquid culture: Pick a loop of bacterial moss from the slant culture of the strain, inoculate it in the broth culture medium, and culture it at 3TC for about 12 hours.
This bacterial solution is the seed culture solution. ^[3]

(2) Dispensing the culture medium and correcting the zero point: Pipet 25mL of culture medium with a sterile pipette and add it to a conical flask with a side-arm test tube. Pour the uninoculated culture into its sidearm test tube and adjust the zero point on the photoelectric colorimeter. Even if the OD value on the photoelectric colorimeter is at zero. ^[3]

(3) Inoculation and zero time measurement: 2. Pipette 2. SmL seed culture solution into the inoculation bottle with a pipette and shake well. The freshly inoculated culture solution was poured into a lateral arm test tube, and the photoelectric colorimeter OD value was measured. The reading at this time is the zero-hour reading in the growth curve of the bacteria after inoculation (ie, inoculation swab).
(4) Cultivation and growth measurement The conical flask immediately after the zero-hour measurement was immediately placed in a thermostatic water bath shaker, and the culture temperature was 3TC, and the frequency of the shaker was about 100 times / min (temperature and frequency can be adjusted at any time). During the culture, the Erlenmeyer flask should be removed from the shaker every 30 minutes, the bacterial solution should be poured into the side-arm test tube, and the OD value should be read on the photoelectric colorimeter. Record each measured data. In each measurement, the zero of the photoelectric colorimeter should be corrected with the culture solution of the blank control tube.
(5) Draw the growth curve: Take the measured time as the abscissa and the logarithm of the number of bacteria (OD value) as the ordinate. Draw a dot on the semi-logarithmic coordinate paper, and the obtained curve is the measured shade under the experimental conditions. Growth curve. ^[2]