Answer to Question #337896 in Microbiology for sasha

Question

How should we go about isolating potential bacteria with antibiotic producing capabilities from the soil. and How would I confirm that your isolates are capable of producing antibiotics?

Answer 1

Serial dilution and spread-plate method is a good starting point in order to isolate bacterial colonies from soil.

Primary and secondary screening for antibiotic production can be done by single line cross streak and agar cup assay respectively against test organisms (For example: E. coli, S. aureus, P. aeruginosa). 

Also for isolation and screening of microbial isolates can be used soil sprinkle technique. 

For this purpose you need to sprinkle 20-30 particles of soil on the surface of nutrient agar plates seeded with the test organism. Then incubate plates at 30°C for 24 hours. Antibiotic activity must be checked by a zone of inhibition, surrounding a colony.