Experiment 18 determination of microbial size

1、 The basic principle is that the cell size of microorganisms is one of the morphological characteristics of microorganisms, and also one of the basis for classification and identification Because of its small size, it can only be measured under a microscope The tools used to measure the size of microbial cells are eyepiece micrometer (Figure Ⅳ - 4) and microscope platform micrometer (Figure Ⅳ - 5) The stage micrometer (Figure Ⅳ-5) is a glass slide with bisector in the center Generally, 1m m is divided into 100 grids (or 2mm is divided into 200 grids), and the length of each grid is equal to 0.01mm (106 μ m) It is specially used to calibrate the length of each cell of eyepiece micrometer Eyepiece micrometer (Figure Ⅳ-4, a) is a small round glass slide which can be placed on the partition plate in the eyepiece The scale engraved in the center is divided into 50 small grids or 100 small grids Each 5 small grids is separated by a long line Because the magnification of the eyepiece and the magnification of the objective lens are different, the actual length represented by each small cell of the eyepiece micrometer is also different Therefore, the eyepiece micrometer cannot be directly used to measure the size of microorganisms Before use, the eyepiece micrometer must be used for correction to obtain the relative value of each small cell of the eyepiece micrometer under the eyepiece and the objective lens with a certain magnification And then it can be used to measure the size of microorganisms 2、 Equipment: Bacillus subtilis staining slide specimen, eyepiece micrometer, mirror platform micrometer, microscope, mirror cleaning paper, cedar oil, etc 3、 Operation step 1 Calibrate the eyepiece micrometer (1) place the eyepiece micrometer to take out the eyepiece, unscrew the eyepiece lens, put the scale of the eyepiece micrometer face down on the diaphragm in the eyepiece cylinder (Fig Ⅳ-4, b), then screw on the eyepiece lens, Zui and insert the eyepiece into the cylinder (Fig Ⅳ-4, c) (2) place the stage micrometer and place the stage micrometer on the stage of the microscope, with the scale facing up (3) to calibrate the eyepiece micrometer, first use a low power mirror to observe and align the focal length When the eyepiece micrometer is seen clearly, rotate the connecting eyepiece to make the scale of the eyepiece micrometer parallel to the scale of the eyepiece micrometer Move the pusher to make the two pairs of scale lines in a certain section of the eyepiece micrometer and the platform micrometer completely coincide, and then count the number of grids between the two pairs of coincide lines (Fig IV (-6) According to the number of grids occupied by the coincidence line between the eyepiece micrometer and the platform micrometer, the actual length of each grid represented by the eyepiece micrometer is converted by the following formula The length of each small grid of eyepiece micrometer (μ m) = the length of each small grid of eyepiece micrometer under high power mirror and oil mirror calibrated by the same method 2 Determination of cell size After the eyepiece micrometer is calibrated, remove the microscope platform micrometer, replace it with the Bacillus subtilis staining slide specimen, calibrate the focal length to make the cell clear, rotate the eyepiece micrometer (or rotate the staining specimen), measure the length and width of Bacillus subtilis in several grids, multiply the measured grid by the length of each grid represented by the eyepiece micrometer, and then the size value of this single cell can be converted In order to represent the size of the bacteria, it is necessary to measure 10 to 20 bacteria on the same smear and find the average value And it is generally measured by the bacteria in logarithmic growth period 3 Take out the eyepiece micrometer, put the eyepiece back into the lens barrel, and then wipe the eyepiece micrometer and the platform micrometer with the wiping paper respectively, and put them back into the box for storage 4、 Test report (1) fill in the correction results of eyepiece micrometer in the following table (2) Fill in the following table with the results of measuring the size of Bacillus subtilis under high power microscope