lab of microbiology

Please answer the following questions. Your answer for each question should be a minimum of 150 words (half page). Please number your answers with the number of the question you are answering.

1.
Koch was the first scientist to prove that bacteria actually cause disease. He scientifically demonstrated that a disease is caused by a particular organism. He created four general guidelines to aid in identification of disease causing pathogens. These guidelines developed from his work with purified cultures of anthrax that had been isolated from dead animals. Koch also proved that the same disease could be passed from one organism to another. Pasteur proved that microorganisms could be present in non-living matter. Bassi passed both Pasteur and Koch in the discovery that many diseases of both man and animal were caused by parasites. This was important in the formulation of the germ theory, to which both Pasteur and Koch would later expound. Bassi and Pasteur, though their research was important to later research, did not discover the true cause of disease, and were not able to isolate the causal organisms. Koch was not only able to isolate the causal pathogen, he was able to relate a specific pathogen caused a specific disease. We use his postulates because they provide accurate data.

2.
Through this letter I would like to present my opinion regarding Grams staining method and reliability of this method. According to me, Grams staining process is a simple technique that assists in recognition of etiological agent and therefore can be called as one of the most significant staining practices in microbiology. Though, Gram is concerned that the staining process developed by him is imperfect because not all bacteria can be stained by it, but in my opinion, when we pour ethanol over the slide to wash away the dye then only definite bacteria can retain the color whereas other species bleach. Such difference might be due to the composition of their cell- wall. In fact, initially all bacteria may get colorized (purple) by crystal violet stain then because of adding up iodine, crystal violet are decolorized by those that cannot retain the crystal violet.

3. The cell walls of gram-positive bacteria are made up of twenty times as much murein or peptidoglycan than gram-negative bacteria. The thick outer matrix of peptidoglycan, teichoic acid, polysaccharides, and other proteins serve a number of purposes, including membrane transport regulation, cell expansion, and shape formation.

Almost all bacteria can be classified as gram-positive or gram-negative. The classification relies on the positive or negative results from Gram’s staining method. Because gram-positive bacteria have more layers of peptidoglycan in their cell walls than gram-negative, they can retain the dye. Both gram-positive and gram-negative bacteria have a cell wall made up of peptidoglycan and a phospholipid bilayer with membrane-spanning proteins. However, gram-negative bacteria have a unique outer membrane, a thinner layer of peptidoglycan, and a periplasmic space between the cell wall and the membrane. In the outer membrane, gram-negative bacteria have lipopolysaccharides, porin channels, and murein lipoprotein all of which gram-positive bacteria lack. As opposed to gram-positive cells, gram-negative cells are resistant to lysozyme and penicillin attack. The gram-negative outer membrane which contains LPS, an endotoxin, blocks antibiotics, dyes, and detergents protecting the sensitive inner membrane and cell wall. LPS is significant in membrane transport of gram-negative bacteria. LPS, which includes O-antigen, a core polysaccharide and a Lipid A, coats the cell surface and works to exclude large hydrophobic compounds such as bile salts and antibiotics from invading the cell. O-antigen are long hydrophilic carbohydrate chains that extend out from the outer membrane while Lipid A anchors the LPS to the outer membrane. A staining technique used to classify bacteria is stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranine. Gram-positive bacteria retain the violet stain; gram-negative bacteria do not. That means gram-negative bacteria is decolorized with alcohol. LPS is significant in membrane transport of gram-negative bacteria. LPS, which includes O-antigen, a core polysaccharide and a Lipid A, coats the cell surface and works to exclude large hydrophobic compounds such as bile salts and antibiotics from invading the cell. O-antigen are long hydrophilic carbohydrate chains (up to 50 sugars long) that extend out from the outer membrane while Lipid A (and fatty acids) anchors the LPS to the outer membrane. A staining technique used to classify bacteria in which a bacterial specimen is first stained with crystal violet, then treated with an iodine solution, decolorized with alcohol, and counterstained with safranine. Gram-positive bacteria retain the violet stain; gram-negative bacteria do not. That means gram-negative bacteria is decolorized with alcohol.

4. You look in the refrigerator and find an orange drink you had forgotten was there.
The drink now has an off-taste and bubbles. What is the most likely explanation for the changes in the drink?

Fermentation of the sugars (the bubbles are CO2, the off taste is caused by some sugar having turned into alcohol and/or vinegar). Fermentation is anaerobic metabolism of the pyruvic acid produced in glycolysis. Carbon dioxide is released in this process thus making bubbles in the orange juice. The off taste is formed probably by bacteria or the acid. There are many different types of fermentation and most fermentation are used for in making bread and wine. It is also common in yeast to make it rise.

5.

Psychrophilic microorganisms have evolved to withstand the pressures of living in cold environments, not hot environments Although they live at temperatures of 15 to 20 degrees, centuries of evolving have made this possible. A hyperthermophile is an organism that thrives in extremely hot environments. Yes it is possible to isolate hyperthermophilic microorganisms from cold water enviorments. They can be found in zones of optimum growth temperatures just like geysers. In deep channels they can be found at the greatest depths and the least heat tolerant near the surface where the water is cooled.

6.

In the first there would be less of them because its less than its normal temperature. In the second one since its 37 degrees it would be at the optimum temperature thus creating the maximum number of bacteria in the culture. Number 3 since its anaerobic meaning it can grow without the presence of oxygen then it would be no change. For numbers 4 5 6 they would both grow more because lactose and double glucose was added in the medium. For the last 2 it would have less growth because cooling the culture would result in a lot of the bacteria starting to die off and same goes for autoclaving it as well

7.
The media that are chemically defined is the 4th one because of the generation times. It has 100 which means that its producing generations at 100 min. This shows a stable growth for Psedomonas aeruginosa. This can also be said for the last one since it shows stable growth for almost all the bacteria. They all have generation times except nitrobacteria for MGs04 19 amino acids showing somewhat of a stable growth compared to all the other media. And also the 2nd can also be a media that is chemically defined as it also does what the other 2 do as well