Examination of Bacteria and Preparing a Pure Culture

When we returned to the lab on Tuesday, we found that a lot of bacteria had grown in the agar plate. It was now completely covered in the bacteria that we collected from a brick that came in contact with the water from the Ohio river. Much more bacteria grew than what would usually be expected because we left it in the incubator for the whole weekend.

At first glance we were able to see the many different kinds of bacteria. We differentiated them based on different colors and shapes.

Upon further investigation under a microscope, we were able to see many more differences. We even found this filamentous bacteria.

Our next step was to obtain a pure culture. We first sterilized our inoculating loop to make sure only bacteria from our sample would be collected.

Next we lightly touched the different types of bacteria from our sample with the loop, in order to obtain a bead of bacteria. Then to obtain a pure culture we used the streaking method on a clean agar plate. We took the loop and spread the culture in a back and forth motion in one quadrant of our agar plate. Then, slightly over lapping the corners of the quadrants, we repeated the streaking for quadrants two, three and four sterilizing the loop between each new quadrant. 

When we finished this method we sterilized our inoculating loop once more and placed our agar plate upside down in the incubator. Now we just have to wait until the next class to see the pure culture that will form.