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MICR 202L
Quiz 2
| Question | Answer |
|---|---|
| The gram stain reveals what 3 things about a microbe? | 1. its cell shape 2. its cell arrangement 3. its cell wall structure |
| When was the gram stain developed and by whom? | 1884 by Hans Christian Gram |
| Why do Gram-positive bacteria trap purple dye? | they carry a thick layer of peptidoglycan |
| What are the 4 reagents used in the gram-stain procedure? | primary stain, mordant, decolorizer, counterstain |
| What is the primary stain in the gram-stain procedure? | crystal violet |
| What is the mordant used in the gram-stain procedure? | Lugol's iodine |
| What is the decolorizer used in the gram-stain procedure? | ethyl alcohol |
| What is the counterstain used in the gram-stain procedure? | safranin |
| What does the crystal violet do in the gram-stain procedure? | it is the primary stain so all of the cells take up the purple die in the first step of the staining procedure |
| What does the Lugol's iodine do in the gram-stain procedure? | it is the mordant so it intensifies the crystal violet by forming a large crystal violet I complex that gets trapped inside the thick peptidoglycan layer of gram-positive bacteria |
| What does the ethyl alcohol do in the gram-stain procedure? | it is the decolorizer so it strips the outer membrane from gram-negative cells which lose the crystal violet I complex and become colorless |
| What does the safranin do in the gram-stain procedure? | it is the counterstain so it stains gram-negative cells pink |
| In a gram-stain, what color do gram-negative cells stain? | pink |
| In a gram-stain, what color do gram-positive cells stain? | purple |
| You make a mixed smear, and you know that one microbe is a gram-positive and the other is a gram-negative. But when you observe your smear under the microscope, you see only pink cells. What went wrong? | too much alcohol or old culture |
| A student accidentally uses water instead of ethyl alcohol in the gram-staining procedure. What color would you expect a gram-positive microbe to be? What color would you expect a gram-negative microbe to be? | positive and negative would be purple |
| You focus your cells under the 10x lower power objective, but you can't see anything when you switch to the oil immersion lens. What went wrong? | slide was upside down |
| What stain is used to identify the tuberculosis pathogen, Mycobacterium tuberculosis and the microbe that causes leprosy, Mycobacterium leprae? | acid-fast stain |
| What are the cell walls like of acid-fast bacteria? | rich in wax-like lipids called mycolic acids |
| When acid-fast microbes are stained, what happens? | they retain their color when decolorized with acid alcohol, which is why they are called acid-fast organisms |
| What is the primary stain for an acid-fast stain? | carbol fuchsin |
| What color is carbol fuchsin? | red |
| What does the carbol fuchsin do in the acid-fast stain? | it is the primary stain, so it contains phenol, which helps the carbol fuchsin penetrate the waxy, cell wall lipids |
| What is the mordant for an acid-fast stain? | not really a reagent at all, it's time |
| How does the mordant work in an acid-fast stain? | the mordant is time, you need to give the phenol an opportunity to breach the acid-fast cell wall, the carbol fuchsin is allowed to sit on the cells for 10 minutes |
| What is the decolorizer for an acid-fast stain? | acid alcohol |
| What does acid alcohol do in the acid-fast stain? | non-acid-fast cells (microbes with relatively normal cell walls) will lose their red stain and become colorless |
| What is the counterstain in an acid-fast stain? | methylene blue |
| What does the methylene blue do int he acid-fast stain? | is used to counterstain the non-acid-fast cells under a microscope blue |
| In an acid-fast stain, what color do acid-fast microbes stain? | red |
| In an acid-fast stain, what color do non-acid-fast microbes stain? | blue |
| Why must you wear gloves during an acid-fast stain? | carbol fuchsin dye contains phenol, which is a possible carcinogen |
| Why is the acid-fast stain so useful in diagnostic microbiology? | very quick --> can save patient's life |
| Compare and contrast the cell wall structures of gram-positive, gram-negative, and acid-fast bacteria. | gram-positive - thick, lots of peptidoglycan, dyes purple; gram-negative - thin, little peptidoglycan, dyes pink; acid-fast bacteria - gram-positive, high lipid |
| Bacteria normally reproduces by what? | binary fission |
| What are the 3 key steps of binary fission? | 1) DNA replication 2) formation of a crosswall between the two genome copies 3) separation of the cells |
| Years of the misuse of antibiotics has led to what? | bacterial Mutation-Acquired Resistance to Antibiotics |
| NAS is what type of media and what does that mean? | selective medium - this medium will kill most microbes so we are selecting for only the cells that have acquired a mutation that allows for them to grow |
| Does binary fission always produce 2 genetically identical cells? | usually but in very rare cases, no, due to mutations |
| Multi-drug resistant bacteria are an important healthcare concern. Why? Why has this problem arisen? What can be done to combat the problem? | we can't help them, we have to hope that their own immune system can take care of it (give fluids etc). over use and unnecessary use of antibiotics. conservative (wise) use of antibiotics |
| You have cold-like symptoms and feel crappy. There is no evidence that you have a bacterial infection, but you really want to feel better, so you insist on taking antibiotics. Should your doctor prescribe antibiotics? Why or why not? | no - colds are viruses and antibiotics have no help |
| What type of microbes require oxygen for growth? | obligate aerobes |
| What type of microbes cannot grow in the presence of oxygen and may even be killed if oxygen is present? | obligate anaerobes |
| What type of microbes can grow aerobically or anaerobically, but grow more quickly when oxygen is present? | facultative anaerobes |
| Molds are almost entirely what kind of microbes? | aerobes |
| Yeasts are usually classified as what kind of microbes? | facultative anaerobes |
| What is defined by water movement? | osmotic pressure |
| Water tends to move from areas of ___ solute concentration to areas of ___ solute concentration. | low --> high |
| In a ___ solution, when water moves in and out of a cell at an equal rate and the cell is in equilibrium. | isotonic |
| Cells are happiest in what type of solution? | isotonic solution |
| What a cell is in a ___ solution, the concentration of solute outside the cell is less than the concentration of solute inside the cell. | hypotonic |
| In a hypotonic solution, water moves into the cell, causing the cell to expand and potentially burst, this process is called what? | plasmoptysis |
| When a cell is in a ___ solution, the concentration of the solute inside a cell is less than the solute concentration outside the cell. | hypertonic |
| In a hypertonic solution, water moves outside of the cell, causing it to become dehydrated and shrinks so growth is inhibited, this process is called what? | plasmolysis |
| What processes are used in food preservation? | plasmolysis to create hypertonic conditions that inhibit microbial growth |
| Why does an obligate aerobe grow only at the top of a TSA deep, while an obligate anaerobe grows only at the bottom? | obligate aerobe needs oxygen which is only present at the top of the tube. obligate anaerobe cannot tolerate oxygen so they grow at the bottom of the tube where there is no oxygen |
| gamma-rays and x-rays are what type of radiation? | ionizing |
| High energy, short-wavelength form what type of radiation? | ionizing radiation |
| What type of radiation can be used to penetrate and kill microbial cells and can be used for sterilizing pharmaceuticals and medical/dental supplies? | ionizing radiation |
| What type of radiation can be used to control the growth of microbes on surfaces? | non-ionizing radiation |
| Visible light is a form of what radiation? | non-ionizing radiation |
| What is the form of non-ionizing radiation other than visible light? | UV radiation |
| What is the process where sunlight is absorbed by a cell and it can transform oxygen into a reactive form that damages the cell? | photooxidation |
| What is the process where visible light can actually promote the enzymatic repair of damaged DNA? | photoreactivation |
| Why was it important to include controls in your experiment? | this is a thing you can compare to, to see if you had viable bacteria in the first place |
| What is the ability to ferment mannitol and the ability to destroy RBCs? | hemolysis |
| What means that it completely lyses RBCs to release iron that it can use to grow? | beta-hemolytic |
| What means it partially lyses RBCs which results in greening of the agar? | alpha-hemolytic |
| Microbes that are unable to lyse RBCs are called what? | gamma-hemolytic |
| What is the appearance of a blood agar with an alpha-hemolytic microbe on it? | partial hemolysis - greening |
| What is the appearance of a blood agar with a beta-hemolytic microbe on it? | complete hemolysis - clearing of blood |
| What is the appearance of a blood agar with a gamma-hemolysis microbe on it? | no change, blood red |
| Mannitol salt agar is selective or differential? | both |
| What salt concentration is in mannitol salt agar? | 7.5% |
| Mannitol salt agar contains a pH indicator that changes what colors in the presence of acid? this indicates what? | pink to yellow --> indicates mannitol fermentaion |
Created by:
kristen465