Bacteria are a class of prokaryotic organisms with short and short shapes and simple structure, which are multiplied by two divisions. They are the most widely distributed organisms in nature. In the microbial experiment, the experimental methods of bacterial counting mainly include the following:
1. Counter measurement method
That is, counting with a blood cell counter. A volume of sample cell suspension was placed in the counting chamber of the hemocytometer and counted by microscopic observation. Since the volume of the counting chamber is constant (0.1 mm3), the number of bacteria in the sample can be calculated based on the number of bacteria in the counter scale. This method is simple and easy to use and results are immediately available.
This method is not only suitable for bacterial counting, but also for yeast and mold spore counting.
2, electronic counter counting method
The working principle of the electronic counter is to measure the change of the resistance of the liquid in the small hole. The small hole can only pass through one cell. When a cell passes through the small hole, the resistance is obviously increased to form a pulse, which is automatically recorded on the electronic recording device.
The method is more accurate, but it only recognizes the particle size and does not distinguish whether it is a bacterium. Therefore, the bacterial suspension is required to contain no debris.
3. Live cell counting method
The commonly used plate colony counting method is based on the principle that each living bacteria can grow a colony. A certain volume of the bacterial suspension is taken for a series of dilutions, and then the quantitative dilution is plated, and the number of viable cells in the culture can be calculated based on the number of colonies cultured. This method is highly sensitive and is a method for detecting the number of viable bacteria. It is also the method adopted by many countries in the world.
Note the use of this method:
1 Generally, the number of colonies with a number of colonies between 30 and 300 is counted, and too much or too little is inaccurate;
2 In order to prevent the colony from spreading, affecting the count, O.001% 2,3,5 triphenyltetrazolium chloride (TTC) may be added to the culture medium;
3 This method is limited to microorganisms that form colonies.
It is widely used in bacteria testing of various materials such as water, milk, food, medicine, etc. It is the most commonly used live bacteria counting method.
4, turbidimetry
The turbidimetry method indirectly measures the amount of bacteria based on the amount of light transmitted from the bacterial suspension. The concentration of the bacterial suspension is inversely proportional to the transmittance within a certain range and is proportional to the optical density. Therefore, the bacterial liquid can be measured by a photoelectric colorimeter, and the optical density (OD value) is used to indicate the concentration of the sample liquid.
This method is simple and quick, but it can only detect suspensions containing a large number of bacteria, and the relative number of bacteria is obtained. For samples with too dark color, this method cannot be used.
5. Determination of cell weight method
This method is divided into wet weight method and dry weight method. The wet weight method is used to weigh the wet cells in a unit volume culture after centrifugation; the dry weight method is centrifuged, and then washed with water and dried in a desiccator to lose moisture and then weighed. .
This method is suitable for samples with high bacterial concentration and is a commonly used method for determining the growth of filamentous fungi.
6, determine the total nitrogen or total carbon
Nitrogen and carbon are the main components of cells, and their contents are relatively stable. The determination of nitrogen and carbon content can infer the quality of cells. This method is suitable for samples with high cell concentrations.
7. The color change unit (CCU)
This method is usually used for microorganisms that are small and cannot be counted by general turbidimetry, such as mycoplasma, because the liquid culture of mycoplasma is completely transparent and appears clear and transparent red, so it cannot be counted by turbidimetry. Since the solid culture of mycoplasma is difficult, it is not easy to count by the cfu method, so a special counting method, that is, the CCU method is required. It is based on the metabolic activity of microorganisms in the medium as an indicator to count the relative content of microorganisms.
Take Ureaplasma urealyticum as an example, the operation is:
(1) Take 12 sterile test tubes, each tube containing 1.8 ml of Ureaplasma urealyticum.
(2) Add 0.2ml of ureaplasma urealyticum solution to be tested in the first tube, mix well, draw 0.2ml from the second tube, and then analogously, 10 times gradient dilution until the last tube
(3) At 37 degrees, the last tube with the color change of the medium is used as the CCU of the test liquid, that is, the maximum metabolic activity of the mycoplasma. For example, the color change of the sixth tube, his relative concentration is 10 Secondary CCU/ml.
In general, turbidimetry and colony counting can satisfy the counting of most bacteria, but for the special microorganisms such as mycoplasma, the CCU method is more suitable.
There are many methods for determining the growth of microorganisms, and various methods have their advantages and disadvantages, and are not applicable in any case. Commonly used in microbiology work are the plate colony counting method, the counter method and the turbidimetry method. As for which method is more suitable for you, it depends on your specific conditions.
CANSPEC quality provides excellent performance, its excellent quality to meet the various needs of your different experiments, spot, product details, scientific instruments, laboratory supplies, Shanghai Chuangsai, mass products special promotions, welcome to inquire!
Bamboo Toothpaste,Bamboo Charcoal Toothpaste,Bamboo Charcoal Whitening Toothpaste,Natural Bamboo Charcoal Toothpaste
Guangzhou China Han Oral Products Co., Ltd. , https://www.gzchinahan.com