Question

Answer and explain please

Question A student infects his E.coli with Bacteriophage Lambda and then spreads his E.coli on a Tryptic Soy agar plate. He looks at his plates 2 days later and see bacteria growing (like a lawn) on his plate. What can he conclude about his bacteriophage infection other than that no infection occurred?

Answer 1

The normal growth condition for E Coli infected with any bacteriophage or by heat shock treatment in agar pates is at 370c for almost 12 hrs. By this time you will get individual healthy colonies of E Coli in the plate.

Main reasons for Bacterial lawn in the plates

1. lawn is observed due to excess incubation period of 2 day (major reason here)

2. The higher concentration of infected bacteria in the culture used for spreading in the plate

3. Absence of antibiotic selection (result in the growth of both infected and uninfected bacteria in the media)