Additional Questions: What would happen if you used too little alcohol on a Gram

Question

Additional Questions: What would happen if you used too little alcohol on a Gram-negative bacterium like E. col? What would you view as the result? Why? The Grom-regatne, boceriml ba Colared purpa n oddhiot to the red Gm te counter stain. As a cesult, you unuld vw am nte purpla Colored caks. This uould Happn becaus not enaigh alcoho wou be presat to remoe tre crystal Viest dye from e Grom-etin bacter 0 - What is considered to be "too old" for a culture of Gram-positive bacteria, like B megaterium, to be used for the Gram stain? O-what would happen if you used an old culture of a Gram-positive bacterium like B megaterium? What would you view as the result? Why? - Describe THREE differences between Gram-positive and Gram-negative cell envelopes. ·Mow does penicillin work to kill bacteria? which type of bacterium is more likely to be killed by penicillin- Gram-positive or Gram-negative - and why? You have a patient that comes in with pneumonia-like systems and you are able to obtain a sputum sample. Using only the Gram stain, how could you tell the difference between bacterial pneumonia (which can be treated with antibiotics) and viral pneumonia (which cannot)? Describe exactly how you would make this determination. 82

Explanation / Answer

1.If little alcohol is used, then the gram negative bacteria will seem like it's gram positive because it will still be bluish from the crystal violet. This is called a "false positive".

2 it means that cultures to be stained are too old not younger.Culture should be younger .it should not be older to 12 to 18 hours .

3 . Old cultures of 0 gram-positive bacteria will appear Gram negative. This is especially true for endospore-forming bacteria, such as species from the genus Bacillus.

4.The major difference between Gram-positive and Gram-negative bacteria is cell wall structure. The Gram-positive bacterial cell wall has two major components, peptidoglycan and teichoic acid. There are also additional polysaccharides and proteins that vary according to species. The outer cell wall is thick and chiefly comprised of murein, a peptidoglycan only found in prokaryotes. The inner surface of this cell wall touches the cell membrane, a lipid bilayer. Gram-positive cell walls have low lipid content, no endotoxin, no periplasmic space, and no porin channel.Gram-negative bacteria have three layers in their cell wall, not counting periplasmic space. Like Gram-positive bacteria, they are surrounded by a cell membrane, but the peptidoglycan layer is thin and does not directly touch the cell membrane. Additionally, the peptidoglycan layer does not contain teichoic acid, although it does contain a murein lipoprotein which binds this layer to the unique outer cell membrane. This outer cell membrane is a phospholipid bilayer that contains lipopolysaccharide (LPS). LPS is the component of the cell wall, which contains Lipid A, or the endotoxin. Also unique in the Gram-negative outer membrane are porin proteins. This allows for the passage of nutrients between the two walls.

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