Microbial Variety

Introduction

It is simply astonishing when considering the great diversity of prokaryotes that surrounds us. The most common of these simple types of organisms that do envelop us at the bacterial level are Archaebacteria and Eubacteria. They are also the smallest cells described during this laboratory. Although their sizes vary widely, the largest ones reach the dimensions similar to those of some eukaryotic protists. Bacteria (currently referred to as Eubacteria) are composed of Gram-positive and Gram negative families, reflecting the presence of either a thick peptidoglycan cell wall or a thin peptidoglycan cell wall surrounded by an outer membrane (Joset and Guespin-Mitchel 1993).

Another exceedingly important distinguishing feature of the prokaryote as compared to the eukaryote is the lack of membrane bound organelles inside the cell. The name Prokaryote comes from old- Greek pro meaning before + karyon meaning nut, referring to the cell nucleus, + suffix -otos, pl. -otes; also spelled (procaryotes") (Wikipedia, 2005). According to Dr. Harris prokaryotes also differ from the more complex eukaryotes by not only the way they build their ribosomes, but also sexual reproduction which is mostly asexual. No meiosis or mitosis happening here, only reproduction by fission. Nevertheless bacteria are very effective "chemical machines"(Dr. Harris 2005).

While some bacteria are heterotrophic, others are saprophytic, parasitic, pathogenic, and even pathogenic. This gives you an idea how diverse bacteria are.

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Studying Microbial Diversity is of great interest to us for many reasons. Because prokaryotes are found in nearly all environments on earth, understanding these bacteria is crucial to each and every organism on this planet. Archaea in particular seem to thrive in harsh conditions, such as high temperatures or salinity. Many prokaryotes live in or on the bodies of other organisms, including humans. Sometimes this leads to a life-threatening bacterial infection, but in many cases the organisms are harmless or even beneficial to the host.

During this lab we had several objectives. They included using a modern approach to sampling microbial diversity in samples that we collected outside, using well-known similarity indices to compare the similarity of samples from different environments. And our final objective was to introduce a concept of microbial community ecology, including functional diversity.

My Null and Alternative hypothesis are as follows:

Ho: The similarity of the three microbial communities represented on our shared plate

will all be the same.

Ha: I predict that Sample A ( pond water ) will contain the most diverse and largest

amount of bacteria, as compared to Sample B and C.

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Materials and Methods

To obtain a wet and dry sample, two basic methods and materials were used. While in the previous years when obtaining a dry sample a cotton swab was being used, now due to inconsistencies of microbes not being picked up by the ecoplates, we used a much simpler and efficient method. That method was a plastic spoon and a plastic cup. When getting a wet sample a whirl-pack was used and seemed to work well.

We began the experiment by examining the Ecoplate without removing the lid. Each group used up 32 of the 96 wells. After we finished examining the Ecoplate we discussed what sample we would gather from an outdoor location. We also consulted other groups on what type of samples they would gather. After deciding to gather a dry sample we used a sterile plastic spoon and a plastic cup to collect our sample. We made sure that we used a sterile spoon and cup to ensure that we are not mixing our bacteria with the bacteria from the sample. The first sample was collected from the pond water, whereas the second sample was dirt that came from underneath the trash can. The last sample was the dirt gathered from the construction area. While keeping our sample well mixed, we used a disposable pipette to add 3-4 drops to each of our 32 wells. Being careful we made sure that we did not let drops splash into other wells.

After all three of the groups finished adding their samples to the Ecoplate we labeled it and gave it to our lab instructors. We finished the day by recording where all the samples were gathered from. After allowing the Ecoplate to sit for five days at room temperature, and then stored in the refrigerator we inspected the Ecoplate and recorded a

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"0" where there was no purple color present and "1" signifying presence of the purple color. The final step in our lab was to find out Jaccard's Coefficient. This simple and popular method was created to answer questions such as: Why are some communities so similar, and others so different? The Jaccard's Similarity Coefficient is Sj = a /(a+b+c) and ranges from 0.0 (which represents a no match) to 1.0 (complete similarity).

Results

Sample A (fountain water) showed a