1. Some bacteria are harmful to humans, but most are not. Provide one example of
ID: 152114 • Letter: 1
Question
1. Some bacteria are harmful to humans, but most are not. Provide one example of a harmful species and one example of a harmless species for each of the three common bacterial cell shapes.
2. List three harmful bacteria that were NOT mentioned in your answer to question 8, along with the conditions they cause. Also, note the cell shape of each.
3. Describe the acid-fast staining technique. What dyes are used? What is the technique commonly used for?
4. Describe the endospore staining technique. What dyes are used? What is the technique commonly used for? Why would it matter if an organism is capable of producing endospores?
Explanation / Answer
3. The Ziehl- Neelsen stain also known as acid-fast staining is a differential stain used to identify microorganisms such as members of Mycobacteria. Acid-fast microbes are the ones wax-like nearly, impermeable cell walls, such as mycolic acid and a large amount of fatty acids, wax and complex lipids. It distinguishes organisms by with waxy cells walls which resist decolourization with acid alcohol. Reagents used in this are carbol fushin, acid alcohol and methylene blue.
4. Endospore staining is differential staining also called the Schaeffer- Fulton method. It is used to distinguish between vegetative cells and endospore. A primary stain malachite green is used to stain the endospores. water is used to decolourise the stain, endospores retain the dye whereas the vegetative cells don't. Endospores help bacteria to survive in extreme conditions. It allows the bacterium to produce a dormant and highly resistance cells to preserve the cells' genetic material in line and in times of extreme stress.
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