mkomtangi's blog

For the Denitrification test, the results showed that there was nitrate present in both the rich and poor soil tubes because when nitrate reagent A and B were added to the Nitrate broth tubes, both turned red, meaning it is positive for nitrate. In addition,  a small amount of gas was found in the durham tubes meaning nitrate was broken down into gaseous products.

For both Proteus vulgaris and Pseudomonas aeruginosa nitrate was broken down into gaseous products because there was a large amount of gas in the durham tubes. In addition, when zinc was added to the tubes, there was no color change meaning it was a positive result and nitrate was broken down into a compound other than nitrite such as nitrogen gas.

For this experiment, I decided to compare the thickness of the shell of the surviving snails in a population that had crabs present and a population that did not have crabs present. I did my experiment on the West side. My Independent Variable was the presence or absence of crabs, the dependent variable was the average thickness of the shell of the snails. The control of this experiment is a tank with no crabs just snails. In this experiment, I did not cull the baby snails. This means that the snails in my experiment can reproduce and I will have baby snails in my experiment.

There were eight tanks in my experiment. I held constant the number of snails and the thickness of snails consistent between the control and treatment tanks. Each tank had 15 snails; 5 of these snails had very thin shells(1-4 mm), 5 had thin shells (4-7 mm) and the last 5 had thick shells (7-10 mm). Four of the eight tanks were my treatment group, they were two crabs in each of the four tanks. The other four were my control group so they did not receive treatment which means there were no crabs in these tanks. I had four tanks in each group because I wanted to have replicates of my experiments.I recorded my data which is the mean of the thickness in each tank, the number of crabs and the snails that survived in each tank. After that, I run the experiment for 120 days. After every 30 days, I recorded the data again till the 120 days had past. I ran the experiment for 120 days to allow the snails to reproduce.

The Nucella Lamellosa commonly known as the Frilled Dogwinkles snails have a life span of eight months. The baby snails normally do not have thick shells like their parents until they reach maturity. This normally happens after 30 days and they are able to reproduce after maturity. Unlike other snails, Dogwinkles are not hermaphrodites, they are gender specific.

The females can not mate for a while after reproducing. Prior to my experiment, I observed that, the shell of the snails on the east side were more thicker compared to the shell of the snails on the west side.This difference could be as a result of natural selection. The snails vary in their population, the thickness of their shells is heritable and there is differential survival when a predator is present.

After my observations, I found that my results were conclusive to my hypothesis. My results of the experiment showed that the pre-pasteurized NA plates contained lots of growth. Large colonies that seemed to be clumped together made it difficult to distinguish and count colonies, yet there seemed to have been one isolated colony present on the plate. The organisms appeared to have a dull texture with an opaque color, and slight elevation. As for the post-pasteurized plate, there was growth present. There was a lack of colonies present in comparison to the pre-pasteurized plate.

Both plates expressed similar colony morphology. Each colony that presented growth on the plate was isolated thus making counting possible. The organisms also presented an opaque color and very dull texture, with slight elevation. When observing the post-pasteurized organisms under the phase contrast microscope, the organisms were bacillus shaped in a chain-like arrangement with lots of movement. Tiny black dots within cells presented endospore formation, however no germination was detected. The post-pasteurized organisms that were gram stained and viewed under the light microscope at a total magnification of 1000x, expressed a  streptobacillus arrangement of organisms with distinct purple color indicating that the organisms were gram positive.

I began my experiment by collecting and labeling two petri dishes, I then added molten GYE to the label portions of my plates and let it solidify. After I added molten water agar into the halves of the petri dishes, again letting it solidify. I then put two pieces of filter paper on the plates creating a bridge for the bacteria to move throughout, I then inoculated the organism on each strip of paper at opposite points from each other, creating a diagonal cross.

    My results for the experiment were again conclusive to my hypothesis. The Serratia marcescens showed large amounts of growth on the inoculated region of GYE and minimal growth on the inoculated region of the water agar, indicating that the organism was attracted to the GYE agar and moved in the directions towards the agar. As for the Enterococcus faecalis, there was hardly any growth on the inoculated water agar, and there was minimal growth on the inoculated GYE region of the dish, proving the the organism is nonmotile, as it hardly moved towards the chemical attractant.

In this experiment Koch’s Postulates were performed in displaying that it truly can prove that particular organism cause a particular disease. Starting off with the first step of koch’s postulates which states the organism should only be present in individuals suffering from the disease and not in healthy individuals. The carrots with disease where examined for signs of infection and compared to carrots that were not infected. What was observed was the carrots looking very dry, having a slightly brown center, musty odor, and mushy when touched. All clear signs of infection. For the second step of Koch’s Postulates which states the organism must be grown in a pure culture away from the diseased individual. The infected carrots were scraped with a loop removing some of its soft rotting carrot flesh onto Nutrient agar plate and MacConkey agar plate.

Temperature is the intensity of thermal energy within a substance or object and can vary
between being hot or cold. When it is too cold cell proteins may be destroyed as ice forms, or as
water is lost, heat coagulates proteins and changes the cell structure and function. Metabolic
activities of microbes, plants and animals are regulated by enzymes and those enzymes are
influenced by temperature, especially increased temperature, up to a certain limit. Increased
temperature brings about increased enzymatic activity, resulting in an increased rate of
metabolism. Temperature can have many effects on an organism, it can affect their cell structure,
metabolism, growth and even their behavior.

For the microbial growth lab, I hypothesized that E.coli, would have the best optimal growth at 37 degrees celsius, as this is the desired temperature for E. coli growth, especially in the cells of humans, animals, and other eukaryotic organisms. I also expect that the k value for 37 degrees celsius which indicates the rate of how many generations occur per time period to be the highest because, it will form the most generations, and the G value which indicates the rate of one cell dividing into two cells to be the lowest because E.coli will divide the fastest at 37° celsius.

For the chemotaxis portion of the motility and chemotaxis lab, I hypothesized that the Serratia marcescens will move towards the nutrient source rather than the Enterococcus faecalis. I expect these results to occur because Serratia marcescens is a known motile organism and reacts in the presence of nutrients and therefore will be chemotactic, this same attraction will occur with the glycerol yeast extract (GYE). I began my experiment by collecting and labeling two petri dishes, I then added molten GYE to the label portions of my plates and let it solidify. After I added molten water agar into the halves of the petri dishes, again letting it solidify. I then put two pieces of filter paper on the plates creating a bridge for the bacteria to move throughout, I then inoculated the organism on each strip of paper at opposite points from each other, creating a diagonal cross.

For the motility portion of the motility and chemotaxis lab, I hypothesized that there would be movement seen for Proteus mirabilis, however there would be no movement for Staphylococcus aureus. I expect these results to occur because the motility agar contains tetrazolium salt, which in its oxidized state the salt is colorless, however when living bacteria is present within the media they reduce the salt content of the medium causing a purple color to display. Therefore when a living organism comes in contact with the salt, the medium will turn purple, this will allow the tetrazolium salt to act as a tracer for movement of the bacteria. This indicates that proteus mirabilis is a living organism and will move from the point of inoculation and spread throughout the medium, displaying a purple color; while the non- living bacteria, Staphylococcus aureus will only grow at its point of inoculation, revealing the purple color on in the site of inoculation.