Isolation of antibiotic producing microbes from soil by crowded plate technique and demonstration of antibiotic sensitivity by giant colony inhibition spectrum PDF

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Isolation of antibiotic producing microorganisms...

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Expt. No 1(a) Isolation of antibiotic producing microbes from soil by crowded plate technique and demonstration of antibiotic sensitivity by giant colony inhibition spectrum A.

Isolation of Antibiotic producing microbes from soil

Aim: To isolate antibiotic producing microorganism from soil by crowded plate technique Principle: Microorganisms are ubiquituous in nature. They can be isolated from different sources in nature like soil, water, sewage, body surface and from plant parts. They are bacteria, fungi, actinomycetes, algae, protozoa and viruses. These organisms have a specific relationship leading to useful or harmful effect of biotransformation and causing diseases. In addition to isolation, enuemeration of microorganisms can be done by several techniques. To isolate a microorganism a suitable media is required. Organism isolated from a particular environment will be a mixed culture. Microorganuism can be isolated in pure culture and can be identified by various biochemical test and the desired organism can be preserved. Screening is another method to isolate desired microorganism from the microbial population. Materials required: Sterile Nutrient agar media, petriplates, L rod, conical flasks, cotton, pH paper, Bunsen burner, parafilm, micropipette Procedure The soil was collected from the college medicinal garden and 1 gm was weighed and added in 100ml of sterile distilled water (10-2 dilution). Serial dilution: 1ml of above soil suspension was pipette out and transferred to test tube containing 9 ml of sterile distilled water (10-3 dilution). Similarly, further dilutions up to 10-5 was carried out. The tube was labeled as 10-3 , 10-4 and 10-5. Following the dilution, the plating was done by spread plate technique. 100µl from 10-2 to 10-5 dilutions were pipetted on to nutrient agar plates and spread plated using L rods. The plates were sealed with parafilm and incubated at 37o C for 24 to 48 hours Observation: The plates with crowded colonies were obtained in 10-2 dilution. Three colonies showed clear zone around them which was free of any microbial growth. Result: Three antibiotic producing bacteria were isolated from the St. Mary’s college medicinal plant garden and were named as A, B, C...