Lab Report Name: Katie Nave Bacterial Morphology Part 1: Viewing Prepared Slides of Common Bacterial Shapes Familiarize yourself with each morphological type to use as a comparative tool for the remainder of the activity. Record your observations. Part 2: Disinfecting Your Area to Use Live Organisms : Part 3: Viewing Live Organisms – Wet Mount Preparation Record your observations. It was hard to tell what I was looking at. There were a number of amoeba shaped cells of varying sizes. There were five darker areas circular in nature. There were also three very large, odd shaped areas with distinct edges.
Part 4: Direct Staining: Record your observations for each sample. Slide One: There were two distinct clusters that were easily noted. All the cells were cocci. Some of the cells were huge while others were practically nonexistent. Slide Two: There were layers of cells. The cells seemed to all be rectangular in nature with varying sizes. There was a distinct circular nucleus in each cell. Slide Three: It seem like there were a lot of layers of “stuff. ” There was a matrix of sorts consisting of all kinds of shapes and sizes. I wasn’t able to find one specifc layer to look at.
I think I was looking at chains of cocci or bracillus. Part 5: Indirect Staining: Examine the stained specimens and record your results. These were much easier to see, especially the plaque stain. I saw distinct chains of varying lengths made up of both cocci and bracillus cells. The messy matrix I noted earlier was no longer an issue. The cheek and yeast smear were also much cleaner. I saw the same shapes as before, just with sharper outlines. Questions: A. What are the advantages of using bleach as a disinfectant? The disadvantages? The advantages of using 70% alcohol? The disadvantages? 0% alcohol mixtures are capable of killing most bacteria within five minutes. However, the mixture is ineffective against spores and has limited effect on viruses. Additionally, the 70% alcohol is flammable. The sodium hypochlorite in bleach denatures proteins in microorgamisms therefore effectively killing bacteria, fungus, and viruses. It works quickly and is inexpensive. The downside is that bleach irritates mucus membranes, skin, and airways. It also decomposes under heat and light and reacts with other chemicals. Bleach will lose its effectiveness after two hours creating a need for a fresh batch with each experiment.
B. List three reasons why you might choose to stain a particular slide rather than view it as a wet mount. ? ? ? Staining provides reliable means for observing bacteria in terms of relative size, morphology, and cellular arrangement. Specific stains can be used to visualize certain structures (flagella, endospores, etc. ) in bacteria. Staining makes bacteria cells more easily viewed. C. Define the following terms: ? ? ? Chromophore: colored portion of the dye Acidic Dye: chromophore resides in negative ion Basic Dye: chromophore resides in positive ion D. What is the difference between direct and indirect staining?
In direct staining the positively charged chromophore of the stain combines with the negatively charged bacterial cytoplasm creating a “direct” stain. In indirect staining an acidic dye forms deposits around the organism leaving the organism colorless hence the name “indirect staining. ” E. What is heat fixing? A means to kill the smeared organism while adhering the smear to the slide. It also alters the organism so that they more readily accept dyes. F. Why is it necessary to ensure that your specimens are completely air dried prior to heat fixing? If they aren’t dry they will boil and the specimen will be destroyed. G.
Describe what you observed in your plaque smear wet mount, direct stained slide, and indirectly stained slide. What were the similarities? What were the differences? The main difference is that I didn’t see much of anything in the wet mount. It all looked like a lot of clear “goo” on a slide. The indirect stained slide was much clearer to me allowing me to see the specific chains of bacteria living amongst my teeth. H. Describe what you observed in your cheek smear wet mount, direct stained slide, and indirectly stained slide. What were the similarities? What were the differences? Again, the wet mount did not prove itself to be f much value. Both the direct and indirect stained slides gave me a clear picture of the cells looked like. I did prefer the indirect staining as the edges of the cells appeared cleaner providing me with a stronger picture. I. Describe what you observed in your yeast wet mount, direct stained slide, and indirectly stained slide. What were the similarities? What were the differences? There is no contest, the wet mount lost again. I still liked the indirect stain the best. I was able to see very clear clusters of cocci due to sharper edges. J. Were the cell types the same in all three specimen sets: yeast, plaque, and cheek?
How were they similar? How were they different? The cells were definitely not the same. The epithelial cells of the cheek were rectangular and much larger than the bacterial cells of the other two slides. Also, there was a visible nucleus in the cheek cells. The yeast and the plaque slide were similar in that they both contained cocci cells; although the arrangement was different. The yeast had clustered cells whereas the plaque had chains. The plaque also appeared to contain bacillus cells were the yeast did not. The bacillus cells were also arranged in chains.