(1) Experimental purpose Understand the holding point of the bacterial growth curve and the principle of measurement, learn to use the turbidimetric method to determine the growth curve of bacteria. (two) experimental principle A certain number of bacteria are inoculated into a suitable liquid medium, cultured at a suitable temperature, and sampled and measured periodically. The logarithm of the number of bacteria is plotted on the ordinate and the growth time is plotted on the abscissa. The curve is called a growth curve. The curve indicates the law of bacterial growth and reproduction under certain environmental conditions. It is generally divided into four periods: delayed period, logarithmic phase, stable phase and decay phase. The length of each period varies with the characteristics of the strain itself, the composition of the medium and the culture conditions. The turbidimetric method is based on the number of bacterial suspension cells and the turbidity is proportional to the transmittance, and the optical density (ie OD value) of the cell suspension is determined by photoelectric colorimeter, which is used to indicate the bacteria in this experiment. Relative growth under conditions. The experiment consisted of three treatments: normal growth, acid addition inhibition and enrichment culture to understand the growth of bacteria under different growth conditions. (3) Laboratory equipment (1) Living material: E. coli. (2) Medium and reagents: 14 pieces of beef paste peptone liquid medium (10 mL each), and concentrated 5 times of beef paste peptone medium. Sterile acid solution (formic acid: acetic acid: lactic acid = 3:1:1). (3) Equipment: 1mL sterile straw, shaker, refrigerator, photoelectric colorimeter, label, etc. (4) Experimental methods method 1) 1) Inoculation: Take 13 test tubes containing beef paste peptone culture solution and label them (indicating the name of the fungus, culture treatment, culture time, group number). Accurately add 0.2 mL of E. coli culture solution to each tube by aseptic method. After inoculation, gently shake to mix the cells. Another non-inoculated culture tube indicates CK (control). 2) Culture: The inoculated culture tube was placed on a shaker and shake cultured at 37 °C. Among them, 9 culture tubes were taken at 0, 1.5, 3, 4, 6, 8, 10, 12 and 14 h after cultivation, and stored in a refrigerator for determination. Add acid treatment. The other two culture tubes cultured for 4 hours were taken out, and 1 mL of the sterile acid solution was added according to the aseptic method. After shaking, the mixture was returned to the shaker, and the culture was further shaken. After 8 hours and 14 hours of cultivation, the cells were taken out and stored in the refrigerator for measurement. Add rich nutrients to the treatment. The remaining two culture tubes were taken out after 6 hours of culture, and 1 mL of beef extract peptone culture solution concentrated 5 times was added by aseptic method. After shaking, the shaking culture was continued, and after 8 hours and 14 hours of culture, it was taken out and placed in the refrigerator. Stored, to be determined. 3) Turbidity: The bacterial culture medium which is cultured at different times and formed different cell concentrations is appropriately diluted to make the optical density value in the range of 0.0-0.4, and the zero-intensity of the uninoculated beef paste peptone liquid medium is used in the photoelectric colorimeter. In the above, a filter having a wavelength of 400-440 nm is used for the turbidity, and the measurement is sequentially performed from the most dilute concentration of the bacterial suspension. Method (2) Escherichia coli is placed in a small test tube containing beef extract peptone culture medium (the test tube should be inserted into the cuvette of the cuvette). The culture was shaken at 37 ° C, and taken out at 0, 1.5, 3, 4, 6, 8, 10, 12, and 14 h, respectively, and the zero point was adjusted by the non-inoculated culture solution, and the colorimetric was measured on a photoelectric colorimeter. When colorimetric, a cassette should be made to cover the culture tube and the colorimetric cell to form a dark room. (5) Drawing a curve The optical density value (OD) of the bacterial suspension was plotted on the ordinate and the culture time was plotted on the abscissa. The growth curve of E. coli under normal growth, acid addition and rich culture was given. If we use the above-mentioned culture of 0,1.5,3,4,6,8,10,12,14h bacterial suspension to measure by the dilution plate method, the number of bacteria in different time is measured, and the ratio of bacteria suspension is compared. The turbid optical density value is plotted on the abscissa, and the standard number of bacteria is plotted on the ordinate. Thus, after measuring the optical density value of the bacterial suspension at any culture time, it can be found on the standard curve. Number of bacteria. This method has been widely used in the industry, it can save a lot of time for diluting the plate measurement, and directly check the standard curve of the optical density value measured by turbidimetry to understand the growth and decline of the number of bacteria in each culture period. Squid Tube,Raw Squid Ring,Flower Cut Squid,Bqf Squid Tentacle And Tubes Zhejiang ocean family co.,ltd , https://www.ocean-family.com