Experimental principle
Many microorganisms can produce some special metabolites during their life activities, and have the effect of selectively inhibiting or killing other microorganisms, such as antibiotics. The antibacterial spectrum of different antibiotics is different. Some antibiotics only have antibacterial effects on a few bacteria. For example, penicillin generally only has antibacterial effects on Gram-positive bacteria, and polymyxin only has effects on Gram-negative bacteria. Antibiotics are called narrow-spectrum antibiotics; while others have effects on a variety of bacteria, for example, tetracycline and oxytetracycline have effects on many Gram-positive and Gram-negative bacteria. These antibiotics are called broad-spectrum antibiotics. .
If the antibiotic-producing strains are inoculated in a straight line on the bean sprouts juice glucose agar medium plate, after cultivation, a bacterial band will grow and some antibiotic will be produced to spread around the bacterial band. Then inoculate some different test bacteria in a straight line perpendicular to this bacterial zone, and it will produce different lengths of inhibitory zone, as shown in Figure IX-3. According to the length of the bacteriostatic zone, the influence of the antibiotic on different microorganisms can be judged. This experiment illustrates the inhibitory effect of penicillin produced by Penicillium chrysogenum on E. coli, Staphylococcus aureus, and Bacillus subtilis.
Experimental reagent
Sprout Juice Glucose Agar Medium
experiment apparatus
Sterile plates, inoculation loops, etc.
Experimental Materials
Penicillium chrysogenum (Peenicillium chrysogenum), E. coli, Staphylococcus aureus, Bacillus subtilis;
Experimental procedure
1. After dissolving the bean sprouts juice glucose agar medium, cool to 45 ° C and pour the plate, solidify for use.
2. Pick up the spores of Penicillium chrysogenum with the inoculation ring and draw a straight line on the plate as shown in Figure IX-3, 1.
3. After inoculation, put it in the greenhouse at 28 ℃ for 2 to 3 days.
4. After forming the moss on the above-mentioned plate, inoculate E. coli, Staphylococcus aureus and Bacillus subtilis from the edge of the band of Penicillium chrysogenum but do not touch the moss with a inoculating ring.
5. Incubate in a greenhouse at 37 ° C for 24 hours.
6. Observe the results.
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