Once we had all of our materials, it was time to plate the bacteria. We turned on the Bunsen burner and waved the loop quickly through the flame to ensure the surface was sterile. Making sure to keep all activity under the burner (again, to prevent contamination), we stuck the loop into the tube of bacteria and picked up a small quantity of bacteria. Then, we transferred the bacteria onto the agar plate using a criss-cross pattern, as shown below.
Bacteria on agar criss-cross pattern. http://teachersinstitute.yale.edu/curriculum/units/2010/3/10.03.01.x.html
Why were the bacteria plated in a criss-cross pattern? This is to ensure that the bacteria do not grow clumped and crowded with one another. This pattern not only ensures a more equal distribution of resources, but also makes it so that individual colonies can be observed as they grow, rather than a mass collection of colonies impossible to study.
It should also be noted that our bacteria culture included a small amount of antibiotic within its medium. The bacteria we were studying possessed resistance to the antibiotic, and thus were not affected by the drug. This again was a preventative measure against contamination- any bacteria that somehow enters the chamber will be killed by the antibiotic, ensuring that the only growing bacteria will be the desired strain of study.
By observing the growth patterns of our strain of bacteria, we can see the expansion of individual colonies. Although I have performed experiments like this before, it was great to be exposed to more lab techniques and practice scientific skills in a real laboratory setting. This meeting was great, and I cant wait for next week's internship meeting!
