There are many bacterial species contaminated with Pleurotus eryngii strains or culture materials, of which Bacillus spores are more common, followed by Pseudomonas fluorescens and E. coli.
First, the harm symptoms
After the mother species was contaminated with bacteria, the surface of the culture medium was moist, some had obvious colonies, some smelled odors, and the mycelium of the Pleurotus eryngii grew poorly or could not grow. After the culture material is contaminated by a large amount of bacteria in the cultivation process, it deteriorates and stinks and rots. In particular, bacterial contamination of the sphagnum species produces a viscous, bacillus-like fluid and a rancid odor.
Second, the incidence conditions
There are many kinds of bacteria that contaminate the culture medium and culture materials, and their sources are also very extensive. There are bacteria floating in the air, bacteria are also found on various organic substances, and bacteria are also common in water. The Bacillus spp. has the highest resistance to high temperatures. The dormant spores it forms must be killed by 121°C high-pressure steam sterilization or regular intermittent sterilization. Therefore, the cold air is not eliminated during sterilization, the pressure is insufficient, or the holding time is not enough, which is an important cause of bacterial contamination. In addition, during the inoculation process, the inoculation room or inoculation box is not completely disinfected and sterilized. Operators do not strictly observe the aseptic procedures, or the bacteria themselves carry bacteria, which is the cause of bacterial contamination. Judging from the conditions of the medium or the culture medium, the pH value is neutral or weak alkaline reaction, and the water content is high, which is conducive to the growth of bacteria. From the perspective of temperature conditions, high temperatures or high material temperatures are favorable for bacterial growth.
Third, control methods
1. Raw material requirements for culture materials. 1 Straw, cotton seed shells, corn cobs and other dry and fresh without mildew; 2 mold must be used for high-temperature compost fermentation processing; 3 mix with clean well water or river water; 4 dry material weight 0.1% 50% carbendazim or 0.1% thiophanate-methyl spices; 5 control the moisture content of culture materials can not be too high, the temperature of the culture room can not be too high.
2. When the parent species is expanded, a small amount of streptomycin or other antibiotics can be added to the sterilized medium to prevent bacterial growth and ensure that there are no bacteria in the strain. However, when streptomycin is instilled into a test tube, it should be performed under aseptic conditions so as to prevent bacterial contamination but to cause mold contamination. The concentration of antibiotics is preferably 100-200 international units per milliliter.
3. In the course of tube transformation or expansion, the first step is to ensure that the culture medium is completely sterilized, and the second is that the entire operation must be performed strictly according to the aseptic procedure.
4. In the production of strains, the expansion of inoculated parent or original species must be guaranteed to be free of bacterial contamination. If wheat is used as a strain, wheat grains without scab and no damage should be used. To prevent high water content and strict sterilization.
5. The pH of the potato sucrose agar medium used should be adjusted to be acidic in order to inhibit bacterial growth.
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Inert separation glue and coagulant were added to the yellow head cap Blood Collection Tube of inert separation glue. The specimens remained stable for 48 hours after centrifugation. The procoagulant can quickly activate the coagulation mechanism and accelerate the coagulation process. The type of serum preparation is suitable for emergency serum biochemical and pharmacokinetics tests. After collection, the mixture was reversed 5-8 times and stood upright for 20-30min before the supernatant was centrifuged and used.
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