Streak for Isolation

​Purpose: 

​

The purpose of this lab was to aseptically transfer E. coli from broth culture to agar plate and streak for isolation of colonies.

​Materials: 

1 LB agar plate

Inoculation Loop

DN Bacterial Culture

Bunsen Burner and Striker

95% EtOH

Vortex



Method: 

1. Rinsed loop in EtOH
2. Sterilized loop with Bunsen burner
3. Vortexed tube culture and flamed tube
4. Streaked first quadrant on previously marked agar plate (see image)
5. Replaced cap & tube to rack
6. Continued streak to 2nd and 3rd sections of the plate
7. Flamed loop and returned to loop storage container
8. Checked plate for crossover in light and saw NO loop streaks in first section. Repeated entire process using the same agar plate

Results and Data: 

After 24 hours of incubation in the bacterial incubator at 37 degrees C I was able to isolate approximately 30 colonies. 



Discussion and Conclusion: 

I need to be more aware of the resistance from the agar on the loop to avoid having to repeat a third or a quad. Also keep a wider margin of space between thirds to avoid too much crossover (too many crossovers between first and second thirds.



This is a new method (to me) of streaking for isolation. In Microbiology we used quarters of the plate. It would be interesting to retry with a mixed culture and 2 plates to see which method works best (for me) for separating different species.