Microbiology and Identifying Bacteria with DNA Sequences February 4, 2015
The objective of this experiment is to understand and differentiate between the different characteristics of bacteria. The prokaryote bacteria examined are a part of the Domain Archaea, and the eukaryotes a part of the Euryachaeota. All types of bacteria have three basic shapes which will be examined. The first is bacillus, which is rod-shaped, the second is coccus, which is spherical, and the third is spirillium, which is a twisted spiral shape. Bacteria can also be differentiated by staining it and observing the characteristics after that. In this experiment gram staining is used and bacteria that are gram positive (blue) have thick layers of peptidoglycan in their cell walls, while bacteria that are gram negative (pink) have less peptidoglycan in their cell walls. Along with gram staining, PCR can be used to identify species of bacteria, as the DNA helps determine the differences between Archaea and other prokaryotes.
To begin this experiment, collect the 8 agar plates from the Hay Infusion Culture. Observe the 8 plates, and count the number of colonies on each plate. Following, answer several questions pertaining to antibiotic resistance. Once answered, prepare four slides, 2 from the nutrients plates and 2 from the tetracycline plates different colonies and observe them under the microscope. Begin by sterilizing a loop over a flame, following scrape a colony off the surface of the agar and place this onto a small drop of water on a slide. Observe the four samples under the 40x and 100x lenses and determine what type of bacteria it is. The next procedure is the gram staining. Begin by sterilizing a loop over a flame, once this is complete scrape a tiny amount of a colony from the agar and mix with a drop of water on a slide. Using a red wax pencil, circle the area around the sample on the slide and remember to label it. Pass the slide through the flame three times, making sure that the bacterial side is facing up. Over a staining tray, pour crystal violet over the slide for one minutes. Following, rinse the slide with water. Then cover the slide with Gram's iodine mordant for one minutes and rinse with water again. Once this is done, flood the slide with 95% alcohol for 10-20 seconds, and then cover the slide with a safranin stain for 20-30 seconds and then wash this off with water. Blot off any excess water and allow the slide to air dry. Observe the slides under the 40x and 100x objectives and observe and take note of the types of bacteria.
The Tet 10^-7 slide had an orange, yellow, and green appearance. There was no motility, and the sample was gram negative. The Nut 10^-3 had a white, yellow, and small dot appearance. There was no motility in the cell, and the shape was rod. Also the cell was gram positive. The Nut 10^-7 had a white dotty, orange, and purple dotty appearance. The cells was nonmotile, circular and had black borders. The cell was also gram negative. The Tet 10^-5 had a dark purple appearance. The cell was nonmotile, star shaped, and in random arrangement. This cell was gram positive.
The primary purpose of this experiment was to gain an understanding of the different types of bacteria and to understand their physical appearances and thus functions. Through the examination of bacteria under microscope, through wet mounts, and gram staining, it is clear that there are many different types.
Identifying Algae and Protists January 27, 2015
The contents of the 500 mL Hay Infusion Culture which were collected from a unique ecosystem on the AU campus, and are considered to be an ecosystem. As within the large ecosystem where the sample was collected, there are unique niches with different types of abiotic and biotic life forms. In the jar there are different types of microorganisms growing on the surface of the mixture and on the bottom of the jar. The purpose of this experiment is to examine the different life forms found in each of these niches and to determine their functions, appearance, whether they are motile or non-motile, and whether they are photosynthesizing, or non-photosynthesizing.
To begin this experiment each group observed their culture, noting the smell, describing its appearance, and taking note of any form of mold or plant shoots. Following, each group should make a wet mount from the two different niches within the sample. Using a dichotomous key they should determine which type of protists and algae are present in each wet mount. Each group member should then draw pictures of the observed organisms and take note of whether they are motile/ non-motile, protozoa or algae, and whether they are photosynthesizing or not. Each organism should also be measured with the ocular micrometer and measurement should be converted to micrometers and recorded.
The ecosystem within the jar had an earthy smell with a hint of mold and old fish tank water. Its appearance was a translucent light brown. The top layer had a dirty film which appeared to be made out of mold, while the bottom of the jar had a settlement of dirt and leaves. The image above describes each organism and illustrates their appearances.
As the purpose of this experiment was to gain knowledge about ecosystems and the vast differences seen within small niches within an ecosystem, observing different protists and algae helped to illustrate this. By using a dichotomous key to differentiate each organism found in the different niches within the ecosystem (jar), the students were able to see first hand how the environment dictates what type of life form can exist. IJ