Experiment 27 determination of growth curve of Escherichia coli

1、 The basic principle is that a certain amount of microorganisms are inoculated in a suitable fresh liquid medium and cultured at a suitable temperature The logarithm of the number of bacteria is used as the vertical coordinate and the growth time as the horizontal coordinate The curve made is called the growth curve Generally, it can be divided into four periods: delay period, logarithm period, stability period and decline period Different microorganisms have different growth curves, and the growth curves of the same microorganism are different under different culture conditions Therefore, the determination of the growth curve of microorganisms is very helpful to understand and master the growth law of microorganisms There are many methods to determine the growth curve of microorganisms, such as blood cell count, plate colony count, weighing, turbidimetric method, etc In this experiment, the turbidimetric method is used to measure the concentration of bacterial suspension Because the concentration of bacterial suspension is directly proportional to the turbidity, the optical density of bacterial suspension can be determined by photoelectric colorimeter to deduce the concentration of bacterial suspension, and the measured optical density value (OD value) and its corresponding culture time can be mapped to draw the growth curve of the bacteria under certain conditions At present, there is a photoelectric colorimeter (Fig Ⅶ-10) which can directly measure the OD value with a test tube As long as a test tube is inoculated and regularly measured with it, the growth curve of the bacteria can be made 2、 Equipment culture 18-20 hours of E.coli culture medium, containing 12 large test tubes of 5ml meat extract peptone liquid culture medium; 72 or 72.1 spectrophotometer, automatic water bath oscillator or shaker, sterile straw, etc 3、 Operation step 1 Number 11 large test tubes containing peptone liquid medium of meat extract, and mark the culture time with a marking pen, i.e 0, 1.5, 3, 4, 6, 8, 10, 12, 14, 16, 20 hours 2 1 ml sterile pipette was used for inoculation, 0.2 ml of E.coli culture solution was accurately drawn each time, and then inoculated into 11 large test tubes of meat extract peptone liquid culture medium which had been numbered After inoculation, shake to make the bacteria mix well 3 The 11 inoculated tubes were placed on the automatic controlled water bath oscillator or shaker, and cultured in 37 ℃ Take out the test tube with the number of corresponding time in 0, 1.5, 3, 4, 6, 8, 10, 12, 14, 16 and 20 hours respectively, store it in the refrigerator immediately, and measure the optical density together with the turbidity after Zui 4 For turbidimetry, the uninoculated peptone medium was used as blank control, and 540-560nm wavelength was selected for photoelectric turbidimetry The bacterial suspension with high concentration was diluted with uninoculated peptone liquid medium, and the optical density value was within 0.1-0.65 When recording the OD value, pay attention to multiply the times of dilution 4、 Experiment report