Microorganism Size Determination Experiment

Summary

Microbial cell size, one of the morphological characteristics of microorganisms, is also one of the bases for taxonomic identification. Since the organism is very small, it can only be measured under a microscope. The tools used to measure microbial cell size are the eyepiece micrometer and the microscope stage micrometer.

Operation method

microscopic method

Principle

A microscope micrometer is a slide with a central portion inscribed with precise aliquots. Generally, 1 mm is divided into 100 squares (or 2 mm into 200 squares), with each square equal to 0.01 mm (i.e. 106 μm). It is used to calibrate the length of each frame of the eyepiece micrometer. Eyepiece micrometer is a small round slide that can be placed on the partition inside the eyepiece, with a precise scale engraved in the center, there are two kinds of equal divisions of 50 or 100 cells, and there is a long line separating every 5 cells. Due to the use of the receiving eyepiece magnification and the receiving objective lens magnification of the different, eyepiece micrometer each cell represents the actual length of different, therefore, the eyepiece micrometer can not be used directly to measure the size of microorganisms, in the use of microscope micrometer must be used before the calibration, in order to find in a certain magnification of the receiving eyepiece and the receiving objective lens under the eyepiece microscope the relative value of the cell, and then can be used to measure the size of the microorganisms. Size.

Materials and Instruments

Bacillus subtilis stained slide specimens
Cedar oil
Eyepiece micrometer Stage micrometer Microscope Microscope Wiper paper

Move

1. Calibration of the eyepiece micrometer
(1) Place the eyepiece micrometer to remove the catch eyepiece, unscrew the catch eyepiece lens, place the scale of the eyepiece micrometer downward on the partition inside the catch eyepiece barrel, then screw on the catch eyepiece lens, and finally insert this catch eyepiece into the barrel.
(2) Place the stage micrometer Place the stage micrometer on the microscope's carrier stage so that the graduated side is facing up.
(3) calibrate the eyepiece micrometer first with a low-power lens observation, focus, when to see the mirror micrometer, turn the eyepiece, so that the scale of the eyepiece micrometer and the scale of the mirror micrometer is parallel to the pusher, move the pusher, so that the eyepiece micrometer and the mirror micrometer of a certain interval of the two pairs of scales completely coincide, and then count the number of grids between the two pairs of coinciding lines of their respective occupations.
The actual length represented by each cell of the eyepiece micrometer is converted from the number of cells occupied between the line of overlap between the eyepiece micrometer and the stage micrometer obtained by counting by the following formula. The same method was used to correct the lengths represented by each small cell of the eyepiece micrometer under high magnification and oil lenses.
2. Determination of bacteriophage sizeAfter the correction of the eyepiece micrometer, remove the microscope micrometer, replace the Bacillus subtilis stained slide specimen, correct the focus so that the bacteria are clear, rotate the eyepiece micrometer (or rotate the stained specimen), measure the length and width of the Bacillus subtilis accounted for a few cells, multiply the number of the measured cells by the length of the eyepiece micrometer for each small cell, you can convert the value of the size of this single organism, in the same smear needs to be measured on the 10-20 In the same smear need to determine 10 to 20 organisms, to find the average value, in order to represent the size of the bacteria. And generally, the logarithmic growth period of the bacterium to be determined.
3. Remove the eyepiece micrometer, put the connecting eyepiece back into the tube, and then wipe the eyepiece micrometer and the stage micrometer with microscope paper, and then put them back into the box for storage.4. Results(1) Enter the results of the eyepiece micrometer calibration in the table below. (2) Fill in the table below with the results of measuring the size of Bacillus subtilis under high magnification.

For more product details, please visit Aladdin Scientific website.

https://www.aladdinsci.com/