User:Cara Chao/Notebook/Biology 210 at AU

January 28, 2016

Lab 3: Identifying and Studying Bacteria

Abstract:

Observations of Hay Infusion Culture: Transect 4, after another week of incubation, has retained its foul moldy odor. There is a thin film of mold covering the surface the water, and the layer of detritus at the base has gotten thicker, which could indicate signs of decomposition. The water has become more clear and there is a white and cloudy layer that has accumulated along the base above the brown detritus. In addition, there is a dry rim that is less than an inch thick above the surface of the water indicating that water has evaporated. As expected, Archaea organisms were not present in this hay infusion; it would have been an anomaly if archaea were found because they generally dwell in extreme environments, and transect 4 cannot be considered as one that is extreme.

Table 1: 100-fold Serial Dilutions Results

The results show that there was a drastic decrease in the overall number of colonies that grew on tet+ plates compared to those on tet- plates. Plates without tetracycline contained colonies that were not able to grow on tet+ plates. Small light green colonies were identified on tet- plates that could not be found on tet+ plates. However, there were colonies that grew on both the tet+ and tet- plates. Both agar types contained tan, white, and orange colonies. Tet+ plates also had fungal growth in the form of fuzzy white colonies, which indicates that there was either fungal contamination or tet+ plates reduced competition and provided room for any fungi in the sample to grow. There are currently twenty-nine different tetracycline resistance genes, tet. If the colonies on tet+ plates, other than those that are fungi, are confirmed to be bacterial colonies, then there is a chance that they have the tet gene which would explain why they were able to grow on tet+ agar.

Colonies Analyzed:

- Tan colony from the 10^-7 -tetracycline agar plate

- Light Green colony from 10^-3 -tetracycline agar plate

- Orange colony from 10^-5 +tetracycline agar plate

- White & fuzzy colony from 10^-5 +tetracycline agar plate

Citations:

Chopra, Ian and Marilyn Roberts. "Microbiology and Molecular Biology Reviews". Tetracycline Antibiotics: Mode of Action, Applications, Molecular Biology, and Epidemiology of Bacterial Resistance. Jun. 2001. National Center for Biotechnology Information. (9 Feb. 2016).

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January 20, 2016

Lab 2: Identifying Algae and Protists

Abstract: From the previous lab, samples of transect 3 were obtained and cultured in a powdered milk and water medium, or a Hay Infusion Culture. The culture was set up using 500mLs of water, 0.1 grams of dried milk, and 10 to 12 grams of samples obtained from transect 3 mixed together in a plastic jar. After a week of incubation in room temperature, the culture was analyzed and samples from the top and bottom layers were extracted and observed. The sample obtained from the top was extracted from a layer of mold with no plant matter around, while the sample from the bottom was extracted from an area around plant matter. Using a microscope, the extracted samples were analyzed and organisms were identified using a Dichotomous key. A culture with agar plates and agar plus tetracycline plates was set up through a serial dilution of 100µL of the Hay Infusion, after it was thoroughly mixed, in 10 mLs of sterile broth.

Since tetracycline is an antibiotic, bacterial cultures will not grow on the agar plates with tetracycline unless. If there is any growth on tetracycline plates, the growth would most likely be fungus or strains of bacteria that contain a tetracycline resistant gene.

Observations of the culture: - Smelled of decomposition; stagnant water from a creek or lake; earthy-dirt scent; smelled moldy.

- Appearance: fluid in the container was murky light-brown color that was still translucent. There was a layer of mold on the top layer of water with a white film-like layer below. On the bottom of the container was an accumulation of settled particles, most likely soil and rocks. The middle area of the medium contained growth in the form of green shoots from plant samples that were collected and roots.

Identified Organisms:

(1) Gonium (40x), Length: 10.0 µm Width: 1.88 µm Small, rice-shaped body that is composed of a chain of smaller green bodies. Motile and ranges in length. Photosynthesizing and motile.

(2) Eudorina (40x), 10.0 µm Small, round body that contains smaller colonies inside what looks like a membrane. Motile and photosynthesizing algae.

(3) Pandorina (40x), 37.5 µm Large, round body that contains multiple colonies inside. Motile and photosynthesizing algae.

Image of Identified Protists:

Serial Dilution:

Materials -

- Four tubes of 10mL sterile broth labeled 10^-2, 10^-4, 10^-6, & 10^-8

- P1000 micropippetor with sterile tips

- 4 nutrient agar plates & 4 nutrient agar plus tetracycline plates

- 100µL of Hay Infusion Culture

- sterile rod

Procedure -

4 tubes of sterile broth were labeled according to their dilution factor; the 8 agar plates (both -tet and +tet) were also labeled according to their dilution (10^-3,1 10^-5, 10^-7, & 10^-9). The Hay Infusion Culture (transect 3) from the previous lab was mixed; 100µL of the mixed culture was extracted using a P1000 and added to the sterile broth tube labeled 10^-2. From this tube, a serial dilution was carried out to 10^-8 dilution. 100µL from each diluted broth tube was removed and added to the corresponding agar plates. The sterile rod was then used to spread the mixture around the agar plates; the rod was sterilized with ethanol and fire.

The Eudorina meets all the needs of life, as described in Biological Science, by Freeman, Quillin, and Allison by having cells, as it is a colony of green algae, acquiring and using energy through photosynthesis and respiration, containing genetic material, replicating through asexual reproduction, and having the ability to evolve as a species.

If the Hay Infusion Culture grew for another two months, one possible outcome would be an increase in the population of the microorganisms. Any physical changes to the culture would most likely be an increase in mold. Selective pressures that may influence populations in the culture may be a decrease in resources (ie. food), which would likely lead to an overall increase in the populations of organisms that can photosynthesize and a drastic decrease in the populations of heterotrophs.

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January 13, 2016

Lab 1: Examining a Transect at American University (AU)

Transect: 3

Location: Transect 3 is a 20x20 meter plot located in the garden behind the AU amphitheater and next to Hughes Hall. It is a quiet area with an abundance of foliage and shade. There is no body of water around the transect. On the day that this transect was analyzed the weather was sunny with clear skies with temperatures around 30 degrees Fahrenheit.

Topography: The transect is surrounded by cement side-walks and stone, and contains a light post and a wooden bench. It also contains bushes, trees, detritus, wood chips and dormant plants.

Biotic Factors: bacteria and other potential living organisms in the soil, leaves, stems, and roots. Abiotic Factors: soil, metal, water, and rocks.

Hay Infusion Culture:

Materials:

- 10-12 grams of transect sample

- 500mLs of deerpark water

- 0.1g of dried milk

- clean plastic jar with lid

A Hay Infusion Culture was set up using the samples collected of the transect. 10 to 12 grams of the collected samples were put into a plastic jar with 500mLs of water, along with 0.1 grams of dried milk. The jar was closed and mix for 10 seconds, then was opened up and left to incubate for a week.