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MB C6 Self Quiz

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gexodamo's version from 2016-09-15 01:52

Section

Question Answer
1. (t/f)The chemical nutrients that are needed for the maintenance and growth of bacteria are collectively termed CHNOPSTrue
2. (t/f)Most cell divisions in bacteria occur by budding in which a small new cell develops from the surface of an existing cell whereas yeasts and some bacteria divide by binary fission in which the nuclear body divides and the cell forms a transverse septum thats eparates the original cell into two cellsFalse
3. Microbial growth is measured by what parameterIncreased size of cellular components...increase in total number of cells
4. cells lose their ability to dvide and dieDecline/death phase
the number of new cells produced equals number of cells dyingStationary phase
Organisms are metabolically active but not increasing in cell numberLag phase
Continous addition of fresh medium which allows cultures to be maintainedchemostat
Organisms divide at an expoential rate with constant generation timeLog phase
A nutrient-rich mix of substances on or in which microorganisms growMedium
5. the length of time it takes a population of cells to doublegeneration time
6. (a)If a bacterial cell that has a generation time of 30 minutes is placed in a suitable sterile nutrient broth at time 0 and allowed to get a logarithmic phase after 3 hours how many cells would there be in the culture (b)If you froe that culture for 1 hour at -80 degrees Celsius then took the culture out of the freezer and placed it at room temperature and then measured cell number after 30 minutes how many cells would be in the culture now(a)64 (b)Most likely around 64.The freezing would prevent growth.During the 30-minute post freexing period the cells are thawing out and probably would not approach a logarithmic phase during this time.Freezing can also kill cells.
9. Bacteria make exoenzymes in order toHydrolyze large molecules to smaller ones so that they can be transported into the bacterium
10. Why do foods containng a high concentration of salt or sugar usually not require refrigeration to prevent their spoilage
11. Some bacteria have complex nutritional requirements because theyLack many enzymes and must therefore be provided with many of the molecules they need for growth
12. The loss of water and shrinkage of a cell in a hyperosmotic environment is known as _____.The enzyme _____ is important to many bacteria because it _____ down toxic hydrogen peroxide. Some bacteria are barophiles and ca only tolerate living under deep water because the water exerts extreme _____ pressureplasmolysis...catalase...breaks...hydrostatic
13. Bacteria that customarily grow near the surface of bodies of water are usuallyObligate aerobes
14. Aerotolerant anerobegrows with or without oxygen
Obligate aerobemust have abundant oxygen
Capnophilelikes carbon dioxide
Microaerophileneeds a small amount of oxygen
Facultative anaerobegrows with or without oxygen
Obligate anaerobekilled by oxygen
15. Bacteria that require moderate to large amounts of salt for their survival are known asHalophiles
16. Which of the following statements about endospores is trueEndospore formation in som ebacteria occurs because of environmental stressors such as a limiting nutrient or extremes in pH...Endospore formation occurs in Bacillus...Clostridium... and a few other Gram-positive genera...When favorable conditions are restored endospores undergo germination or development into a vegetative cell
17. Bacteriological media that are composed of ingredients whose exact chemical compositions are known are calledDefined
18. Blood agar is often used to observe changes in the appearance of the agar around the colonies growing on this medium.This medium could then be calledDifferential
19. (t/f) A bacterial medium that contains 20 grams of beef extract and 10 grams of sodium chloride dissolved in 1 liter of water is a defined mediumFalse
20. MacConkey agar contains the dye crystal violet that inhibits the growth of Gram-positive bacteria and also contains lactose and a pH indicator that allow the detection of lasctose-fermenting bacteria.MacConkey agar is classified asdifferential...selective
21. Which of the following bacterial froups would you expect to be most likely associated with human infectionmesophiles
22. What are the purposes of carrying out the streak plate and pour plate techniques in microbiologyThe streak plate method involves the spreading out of bacteria across a sterile solid surface such as an agar plate.It is done to isolate a single pure colony so it can be picked up to inoculate a pure culture avoiding cross contamination with other ossible species of microbes on the plate.The pour plate method involves serial dilution of a culture of microbes and transferring a measured volume of the dilutions to melted agar...mixing. and plating.In this way pure isolated and separate colonies grow out and in the agar plate.These colonies can be picked and transferred to another plate or medium to obrain a new culture
23. The bacteria that multiply in improperly treated sealed canned food are most likely to beFacultative anaerobes
24. Many diagnostic laboratories use culture systems that contain a large number of differential and selective media.The advantages of such systems are that they use small quantities of media...occupy little incubator space and provide efficient and reliable means of making positive identification of infectious organisms.Which of the following is a common culture system in use todayAnalytical Profile Index (API)...Enterotube Multitest System
25. Which of the following methods allows determination of the specific number of viable cells in a specimenTotal plate count
26. Organisms divide at their most rapid rateb
New cells are produced at same rate as old cells diec
Lag phasea
Log phaseb
Many cells undergo involution and deathd
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