Lab, Day 2: Microbiology's Beginning To Grow On Me

Day 2 of microbiology lab, we started off by pulling our river sample out of the incubator to see if any bacteria had been cultivated.

Our Hypothesis, considering Steubenville water's reputation, was not too far off.  We expected to see considerable bacteria growth, and we did.  Our sample had some of the most growth in the class.  We examined it in detail under a microscope to determine its characteristics.  From what we could see, the colonies were circular, with a cream/tan pigmentation, the edges were smooth (entire), and the elevation of the colony was slightly raised.

Next, we looked to our broth culture to see if there was any bacterial growth, and what kind.  At first, it appeared as though nothing had cultivated in the broth, but when we flicked the bottom of it, a flurry of particles flared up.  This meant, obviously, that they had been cultivated as a sediment, and were resting at the bottom of the tube.  

Finally, we examined the slant cultures.  Significant bacterial growth had occurred in the slants, and they had spread out from the original source of inoculation.  In both slants, the bacteria seemed to develop pointed edges, indicating an echinulate sample.

Progressing to the next experiment in the lab, we prepared a hanging-drop slide in order to better observe the motility of our bacteria samples.  The hanging-drop slide was made by putting bits of vaseline on the corners of a clear coverslip, then using a flamed inoculating loop, we transferred a sample of our broth culture onto the center of the coverslip.  We then put the coverslip onto a depression slide.  The vaseline helped it to stick, but kept it from squishing the droplet sample, allowing it to remain as a sort of "bubble."  Looking at it under a microscope, we discovered an incredible amount of movement for such a small drop of the sample.  Countless bacteria wriggled around, several trying to "swim" through the others.
















In the last section of the lab, we prepared a bacterial smear and performed a simple stain.  Smearing a sample of our agar plate culture onto a slide, we allowed it to air dry, then passed it quickly through the flame a few times to heat fix it.  We then covered it with crystal violet stain for about 30 seconds before rinsing it off.  Finally, we blotted any water from the slide using bibulous paper, and examined it under a microscope.  This time, however, we used a blue light filter on the microscope to show better contrast.  Comparatively, we got a much clearer image.