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    Home > Biochemistry News > Microbiology News > Several detection methods of microbial growth

    Several detection methods of microbial growth

    • Last Update: 2021-01-21
    • Source: Internet
    • Author: User
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    a
    microorganism
    cells constantly absorb nutrients under the right external conditions and metabolize them in their own way. If the speed of assification exceeds the alienation effect, the total amount (weight, volume, size) of its protons increases, and the growth of individuals occurs.
    If this is a balanced growth, i.e. when the cellular parts are growing at an appropriate proportion, reproduction occurs to a certain extent, resulting in an increase in the number of individuals, at which point the original individual has developed into a group. As individuals in the group grow further, this group grows, as measured by its volume, weight, density or concentration.
    the growth of microorganisms is different from the growth of other organisms, the individual growth of microorganisms in scientific research has certain difficulties, usually has no practical significance. Microbes win by volume, so the growth of microorganisms usually refers to the amplification of populations.
    and reproduction of microorganisms is a comprehensive reflection of their interaction with various environmental factors inside and outside. Therefore, growth and reproduction can be used as an important index to study various physiological, biophysic and genetic problems, at the same time, microorganisms in the production practice of various applications or disease-caused, the prevention and treatment of mold microorganisms are closely related to their growth inhibition. Therefore, it is necessary to introduce the detection method of microbial growth. Since growth means an increase in protonic content, the method of assays are also directly or indirectly based on secondary, while the measurement of reproduction is based on counting. Microbial growth can be measured by its weight, volume, density, concentration, and indicators.
    , growth measurement method,
    1, volume measurement method: also known as mycelium concentration method.
    the growth of microorganisms
    measured
    amount of mycelium contained in a certain volume of cultured liquid. The method is to take a certain amount of culture fluid to be tested (e.g. 10 ml) placed in a scaled centrifuge tube, set a certain centrifugal time (e.g. 5 minutes) and speed (e.g. 5000 rpm), centrifugation, poured out of the night, measured the volume of the upper clear night is v, then the concentration of mycelium (10-v)/10. Mycelium concentration determination is an important monitoring index for microbial growth in large-scale industrial fermentation production. This method is extensive, simple and fast, but needs to set consistent treatment conditions, otherwise the deviation is very large, because the centrifugal sediment is mixed with some solid nutrients, the result will be a certain deviation.
    2, dry weight method:
    can be determined by centrifugal
    or
    filtration method. Generally dry weight is 10-20% wet weight. In centrifugation method, a certain volume of culture fluid to be measured is poured into the centrifugal tube, set a certain centrifugal time and speed, centrifugation, and use water centrifugation washing 1-5 times,
    drying
    . Drying can be done in an oven at 105 degrees C or 100 degrees C, or in infrared, or in a vacuum at 80 degrees C or 40 degrees C, after drying weighing. Such as the use of filtration method, silky fungi can be filtered with filter paper, bacteria can be filtered with acetic acid fiber membrane and other membranes, after filtration with a small amount of water washing, vacuum drying at 40 degrees C. Weighing and re-eding is cumbersome, and is often used when obtaining microbial products as bacteria, such as active dry yeast (activity dry yeast, ADY), some feed and fertilizers that use microbial bacteria as active substances.
    3, than turbidity method:
    the growth of microorganisms caused by the increase of turbidity of the culture. The absorption value at a certain wavelength is determined by the ultraviolet terrolight meter to determine the growth of microorganisms. A special triangular flanter with side arms may be used to keep a timed track of the growth of bacteria in a culture. By inserting the side arm into the color base hole of the photoelectromeometer, its growth can be determined at any time without the need for fungicides. This method is mainly used for the monitoring of the growth of fermented industrial fungi. As I use UNICO's UV-visible tradiscometer, the absorbance value of the fermentation fluid OD600 is timed at a wavelength of 600nm to monitor the growth and induction time of E.Coli.
    4, mycelium length measurement method:
    for silky fungi and some line-releasing bacteria, you can determine the length of mycelium growth over a certain period of time on the
    -culture base
    , or use a thin glass tube with an opening at one end with a scale, into a suitable culture base, lie down, inoculated microorganisms at one end of the opening, after a period of time to record the growth of silk microorganisms, to measure the growth of silk microorganisms.
    II, microbial counting
    1, blood cell counting board:
    blood cell counting plate is a special structure scale and thickness of thick glass, the slide has four ditches and two crucibles, central There is a short cross-section and two platforms, the two tables are 0.1 mm higher than the surface of the two platforms, each platform is engraved with different specifications of the grid, the central 0.1 mm2 area engraved with 400 small squares. Through the oil mirror observation,
    statistics
    the number of microorganisms in a certain large grid, you can calculate the number of bacteria contained in 1 ml of bacteria. This method is simple, intuitive and fast, but only suitable for single-celled microorganisms or silky microorganisms produced by spores to count, and the result is the total number of bacteria including dead cells.
    2, staining counting method:
    in order to make up for some microorganisms in the oil mirror is not easy to observe the count, and directly with the blood cell counting board method can not distinguish between dead and living cells, people invented dyeing counting. Proper staining of the bacteria with different dyes makes it easier to count live bacteria under
    microscope
    the microscope. Such as yeast live cell count can be used in the blue dyeing liquid, after dyeing under the microscope to observe, live cells are colorless, and dead cells are blue.
    3, proportional counting method:
    will be known particles (such as mold spores or red blood cells) concentration of liquid and a cell concentration to be tested in a certain proportion of the liquid evenly mixed, in the microscope field of view to count their respective numbers, you can get the unknown cell concentration of the bacteria liquid. This counting method is extensive. It is also necessary to make a standard for suspensions with known particle concentrations.
    4, liquid dilution method:
    to the unknown bacteria samples to do ten consecutive series dilution, according to estimates, from the most suitable three consecutive 10 times dilution of each 5 ml sample, inoculation 1 ml to 3 groups of a total of 15 In a test tube filled only with culture fluid, the number of test tubes with each dilution growth is recorded after culture, and then the maximum or indimensium table MPN (most probably number) is checked to arrive at the number of bacteria in the sample, and the live bacteria content is calculated according to the sample dilution multiply. The method is commonly used for the detection of microorganisms in food, such as microbial limits for drinking water and milk.
    5, flat-panel bacterios counting method:
    this is the most commonly used live bacteria counting method. The liquid to be measured is gradiently diluted, a certain volume of diluted bacteria is mixed with a suitable solid culture base before solidification, or the bacterial fluid is coated on a solid culture plate that has solidified. After insulation culture, the number of bacterios appearing on the plate multiplied by the dilution of the bacteria liquid, you can calculate the number of bacteria in the original bacteria. It is generally appropriate to have 50-500 bacterios on a plate with a diameter of 9 cm. But the method is more troublesome, the operator needs to have skilled technology. Flat-panel bacterios counting method can not only get the number of live bacteria in the bacteria, but also the bacteria in the bacteria in the liquid for a separation culture, obtained monoclonal.
    6, reagent paper method:
    on the basis of tablet counting, the development of small commercial products for rapid counting. The form has small thick filter paper,
    agar
    and so on. A suitable medium is sucked in the filter paper and agar tablets, wherein the active indicator 2,3,5-chlorinated tribenzene tetraazole (TTC, colorless) is to be cultured in a sealed bag after taking the test bacteria solution. After short-term culture, a certain density of rose-colored tiny bacteria on the filter paper can be compared with the standard paper slab map to estimate the bacteria content of the sample. Reagent paper count is fast and accurate, which avoids the man-made operation error of tablet counting.
    7, membrane filtration method:
    with a special membrane to filter a certain volume of bacteria-containing samples, dyed by ya ding orange, under the ultraviolet microscope to observe the cell fluorescence, live cells will be orange fluorescence, and dead cells green fluorescence.
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