Day 3 - Create Streak Plate, View Living Bacteria, and Test Host Specificity

Today, after following normal entrance protocol, of course, we gathered our streak plates and broth cultures from yesterday. Let's see what we grew. 

Woah! Just look at that bacteria!

Part One

First, we prepared a streak plate with the broth cultures that we had incubated. The streak plate should separate the cultures into colonies that we can later analyze more closely. 

Disinfecting our wire loop before preparing the streak plate. 

The procedure to prepare the streak plate was as follows according to the aseptic technique: (1) We first disinfected the wire loop. (2) We opened the top of the broth culture and (3) disinfected the top both before and after.  (4) We then inserted the wire loop into the culture taking out a droplet with it.  (5) We put this on the streak plate in the pattern shown in the previous post.  (6) Lastly, we set this into the incubator at the 25 degrees C and will look at it again tomorrow.

Part Two

Next, we viewed the movement of the bacteria we grew. We  looked on page 84 of our lab book Techniques in Microbiology: A Student Handbook.

To do this, we needed to prepare a hanging drop slide, which will allow us to see the movement of the bacteria. We took a depressed slide, one that has a circular depression in the middle, added Vaseline to the corners of the cover, and placed a drop of our bacteria on the cover. After doing this, we placed this on top of the depressed slide. The virus should be able to swim back and forth, allowing us to see it clearly.

We, after a little help from Dr. Joseph, found some lively bacteria, moving up a storm. This video represents what we saw, but doesn't show the movement as well. 

After this video, we took proper measures to dispose of the slide and moved on to the next topic.

Part Three

The last thing that we did today was test viruses for host specificity. The best way to do this is to look at bacteriophages and see what different bacteria they will and won't attack.

Bacteriophage

A bacteriophage is a virus that will infect a bacterial cell. They do not have a wide host range, meaning that they are very specific as to what type of bacteria they act against. In our experiment, we tested two types of bacteria (Staphylococcus aureus and E. coli) with one bacteriophage.

The procedure for this was done by Dr. Joseph in the lab. He first labeled the back of the test tube with FUS so that we can see where the bacteria will not grow. He then swabbed the whole surface of an agar test plates with bacteria, one for each bacteria being tested. Next, he added the bacteriophage to where the FUS lines were. We put this into the incubator and will wait until tomorrow to see what comes of it!

*App of the Day - The host specificity is why we do not have to worry about getting diseases such as cow pox from other animals. These diseases are specifically aimed at the host that they naturally occur on. They may affect us in a limited way if we humans are close to the species being affected. For example, cow pox will not cause the full disease in humans but may cause skin lesions. But, bacteriophages which are viruses meant to attack bacteria will not affect a human host in any way, because the genetic make-up is so different. The spread of swine flu developed off of a mutation that came from the origination swine disease, but mutated enough to now to affect humans as well.