Introduction to Prokaryotes

Custom Student Mr. Teacher ENG 1001-04 11 October 2016

Introduction to Prokaryotes

Prokaryotes are single-celled organisms that can survive in extreme environments. Bacteria is the more numerous type of prokaryotes. The group hypothesizes that the samples taken from different environments will all cultivate diverse morphology in fast growing rates in each environment. The aseptic technique was used to cultivate bacteria from different environments. The diversity of morphology and the growing rate of the bacteria was different in each environment. Introduction Prokaryotes are the oldest known life-forms, having existed for the last 3. 5 billion years. Microscopic in size, they are single-celled organisms.

Prokaryotic species can survive in extreme habitats that the other life-forms are not capable of inhabiting. Prokaryotes have different shapes, the three most common shapes are spherical (cocci), rod shaped (bacilli), and spiral (spirilla). The prokaryotic cellular structures are unique to their classification. Prokaryotes have an external cell wall and a plasma membrane. The cell wall keeps the shape of the cell, protects the cell, and averts the cells from bursting in a hyposmotic environment. Prokaryotic cells contain a unique material called peptidoglycan (Sadava et al. , 2011).

Also metabolic diversity is among the criteria used in classifying prokaryotes. The term nutrition refers to the means an organism uses to obtain two energy sources: energy and a carbon source. Carbon sources may be either organic, meaning from a living organism, or inorganic, such as carbon dioxide. Prokaryotes split into two lineages known as Archae and Bacteria. The Bacteria are more numerous than the Archae. Bacteria can be endospore-forming bacteria. Bacteria that form endospores are able to survive harsh and severe conditions. Bacteria can also be Enteric Bacteria, they inhabit the intestinal tracts of animals.

One species is Escheria coli. Wild-type Escheria strains are able to grow on a variety of carbon and energy sources, such as sugars and amino acids. Some strains of Escheria are pathogenic. The detection of Escheria coli in water is a sign of contamination. Another group of pathogenic enteric bacteria are members of the genus Salmonella. These members are responsible for food poisoning and typhoid. Prokaryotes play very important roles in our environment. They are involved in the cycling of nutrients and elements in a variety of ways. Many prokaryotes are decomposers that metabolize organic compounds in dead organisms.

These decompositions processes result in the return of vast quantities of carbon dioxide, inorganic nitrogen, and sulfur to our ecosystems. Other species are important as symbiotic partners with other organisms (Walsh et. al. , 2010). The diversity of the prokaryotic world is huge, and to have a better sense of knowledge of bacteria diversity in different environments an experiment to observe bacteria growth diversity in colder temperature is conducted. The group hypothesizes that the samples taken from different environments will all cultivate diverse morphology in fast growing rates in each environment.

The independent variable in the experiment is the temperature control and the dependent variable is the number of colonies. Materials and Methods Seven different environments were chosen to create bacteria from and cultivated on a nutrient-rich media in eight Petri dishes. The bacteria are cultivated on TSA medium, an all-purpose medium used for cultivating all types of bacteria. Sterile water and sterile swabs are used to sample the bacteria from the environment. To make sure that the bacteria was loosened from the environment and stuck on to the swab, the swab was dipped in the sterile water immediately before taking the sample.

Carefully opened the Petri dish and swiped the swab across the plate in a “Z” pattern. Closed the Petri dish and marked it with its corresponding environment. This was repeated seven times each with a different environment. The first environment was the frame of the classroom chalkboard. The second environment was the chair seat of the classroom. The third environment was the bottom of the shoe of one of our group members. The fourth environment was the floor mat inside the doorway of the Biology building.

The fifth nvironment was the stair railing handle from the stairwell of the Biology building. The sixth environment was the spacebar on the keyboard of the laboratory computer. The seventh environment was the mouthpiece of the water fountain in the Biology building. To enable us to check whether or not our aseptic technique was effective the eight Petri dish was our control plate that was struck with the sterile water only. These streaks with sterile water represent control treatments. The bacteria was incubated at 37°C for 2-3 days and then put into the refrigerator for storage.

Results Two of the Petri dishes had small bacteria diversity and also a slow growth rate- the chair seat of laboratory environment sample and the water fountain mouthpiece sample (Table 1). Three of the Petri dishes had medium bacteria diversity and regular growth- the frame of the chalkboard, the stair railing handle from the stairwell, and the spacebar of the keyboard (Table 1). The other two Petri dishes had medium bacteria diversity and fast growth rate- the bottom of the shoe and the floor mat inside the doorway of the Biology building (Table 1).

The Petri dish with the sterile water streaks had no bacteria growth or diversity indicating our aseptic technique was effective. Discussion The results that were obtained in the experiment did not support the hypothesis that there would be large diversity and fast growing rates in each environment. Every environment sample had its own growth rate and bacteria diversity. The primary reason may be that conditions are rarely optimum. Scientists who study bacteria try to create the optimum environment in the lab: culture medium with the necessary energy source, nutrients, pH, and temperature, in which bacteria grow predictably.

Most of the strains used in the classroom either require oxygen for growth or grow better with oxygen. These bacteria will grow better on agar plates, where air readily diffuses into the bacterial colony, or in liquid cultures that are shaken. Since diffusion of oxygen into liquid depends on the surface area, it is important to have a large surface; volume ratio. This means that cultures will grow best in flasks in which the volume of liquid is small relative to the size of the vessel. Also another factor that affects growth is the nutritional medium. Bacteria grow best when optimal amounts of nutrients are provided.


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  • University/College: University of California

  • Type of paper: Thesis/Dissertation Chapter

  • Date: 11 October 2016

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