User:Juliana Delgado/Notebook/Biology 210 at AU

Observing a Transect at AU January 13th, 2015

For this laboratory procedure, a group of lab students were given a transect at American University to observe a 20 foot dimension and study characteristics of the protists, bacteria, plants, invertebrate, and animals in a given transect. Students went to their transect with a plastic bag to collect samples within their transect. With gloves, students were instructed to carefully collect dirt, weeds, plants, flowers, or any water if present to prepare a Hay Infusion Culture. Water, nets, rocks, statues, and pollution were some of the abiotic factors that were found at the given transect, Transect #4. Biotic factors that were observed included plants, flowers, microorganisms in the soil, squirrels microorganisms in the water. Pictures were also taken to have evidence of what the transect that can be seen below.

Preparing and Plating a Serial Dilution January 20th, 2015

For this lab, students used used their hay infusion culture to make serial dilutions for further the investigation of organisms in the small micro biome that was collected from a given transect. Students were instructed to leave their hay infusion culture (without the lid on) at room temperature in the lab for 7 days. After seven days, the culture began to smell like rotten vegetables and dirt. There was a layer of orange- colored algae that formed at the top of the infusion, while at the bottom of the jar there was dirt, mud, and small pebbles, this can be seen in Figure 2.1. Two samples were taken from the top layer of the jar and from the bottom of the jar. At the bottom of the jar, dirt was found and no microorganisms were recorded. However, after placing the orange algae from the top of the sample under the light microscope, students were able to identify the species using a Dichotomous Key. In Figure 2.1, you can see the species recognized was recorded as _______. The microorganisms observed in the culture seemed to be non-motile, photosynthetic organisms. If the culture was allowed to grow for another 2 months without interruption, the sample would produce a foul odor and continue to grow algae which would be able to support more organisms in the sample. Students then were instructed to make a serial dilution from the sample. A drawing of the dilution that was completed can be seen in Figure 2.3.

"Microbiology and Identifying Bacteria January 27th"

In this lab, students were instructed to characterize and identify different species of bacteria based on motility, gram stain, colony morphology and sequencing of the 16s ribosomal subunit gene. First, one last observation of the Hay Infusion Sample was taken to note any changes in smell or appearance. The appearance of the Culture seemed to have no real change, see figure 3.1. The smell of the culture became more pungent, most likely do to more bacteria growing and reproducing. The agar plates that were made in the previous lab were then taken and analyzed to count the colonies and then calculate the colonies/ mL. A picture of the Agar plates can be seen in Figure 3.2. The data recorded can be seen below in figure 3.3. Although there was not a huge difference in the number of colonies on the plate, the agar type with the nutrient and the tetracycline produced slightly more colonies per mL than the agar type with just the nutrient and no tetracycline. Next, wet mounts and gram stains were made to differentiated different microorganisms in the Hay infusion Culture. In the samples from Transect 4, Cocci bacteria and Palisades were found along with many rod shaped bacterium. It was also found that both plates that were 10x10^-3 both with the tetracycline and without, were both found to be gram positive, meaning they have a thick layer of peptidoglycan in their cell walls, whereas both agar plates that were 10x10^-5 were gram negative. The colony descriptions and cell descriptions can be seen in figure 3.4. below.

Figure 3.3. 100-Fold Serial Dilutions Results. Figure 3.4. Bacteria Characterization