(1) Prevent the water in the culture medium from evaporating, especially when pouring the culture medium. If you pour less, it will be easier to dry out and affect the growth of microorganisms.
(2) Prevent the formed condensed water from dripping on the culture medium and causing bacterial pollution.
(3) Inversion can prevent the colony from spreading to some extent, thus forming a single colony, which is convenient for counting.
There will be water evaporation in the culture medium. When water vapor condenses into water droplets and flows back to the bacteria in culture, it will disperse the bacteria and pollute the colonies, which is not conducive to culture observation, so the solid medium should be inverted.
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Natural culture medium
Natural culture medium refers to a kind of culture medium made of animals, plants or microorganisms, including their extracts. For example. Beef paste peptone medium, wort medium and LB medium.
Commonly used natural organic nutrients include bean sprout juice, corn flour, soil extract, bran, milk, serum, coconut juice and so on. Natural culture medium has low cost, which is not only often used in laboratory, but also suitable for industrial large-scale microbial fermentation production.
Combined culture medium
Synthetic culture medium is a kind of culture medium which is simulated and artificially designed by chemical substances according to the components of natural culture medium. For example. Gauss 1 medium and Charcot medium.
Synthetic culture medium has a certain formula, which has strong repeatability when preparing synthetic culture medium, but compared with natural culture medium, its cost is higher and the growth rate of microorganisms is slower, so it is generally suitable for the research of microbial nutrition demand, metabolism, classification and identification, biomass determination, strain breeding and genetic analysis in the laboratory.
Semi-combined medium
Refers to a kind of culture medium which is made up of chemical reagents and some or some natural ingredients. For example, potato sucrose medium.
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