Exam 2 potential answers

1. What is the difference between exponential growth and logarithmic growth?
Exponential growth is when the bacteria reproduce very rapidly by mainly splitting in two every single generation time. Starts off with 1, then 2, then 4, then 8, then 16 and so on. Bacteria do not live off of exponential growth for their whole life cycle. Logarithimic growth is the other typer of of growth.
-Brandi Burke
Also to figure out how many bacteria you have in the end for exponential growth use
x=2n
where n=the amount of times the bacteria divide and x=the unknown number of bacteria in the end

2. Describe the different phases of the bacterial growth curve.
There are 4 phases of bacterial growth and they are lag, exponential, stationary and death phase.
1. Lag Phase- lag in bacteria division because bacteria need to manufacture enzymes and other parts needed to build new bacteria cells
2. Exponential Phase- rapid growth in population because all division machinery running smooth, bacteria building as fast as possible.
3.Stationary Phase- Numbers of new bacteria EQUALS number of dying bacteria. Very little cell division is occurring. Enter quiescent state or dormant state.
4.Death Phase- Number of dying cells out weighs number of new. Bacteria cells have run out of resources.
-Brandi Burke

3. Compare and contrast the similarities and differences between antibiotics, antiseptics, and disinfectants.
Antibiotics- can be taken internally & target cellular parts specific to bacteria
Antiseptics- safe to use on skin, kills cells in a non-specific way
Disinfectants- used on only inanimate objects, more concentrated that is why we can't use them on skin
- Brandi Burke

4. Do halophiles grow best in very low or high water activity? How are they able to do this?
Halophiles grow in very low water activity. They are able to do this by increasing the water concentration inside their cells.
A Permann
I though they able to grow by increase the solute conc. not water isn't?
Hoa Le

5. What bacteria can grow in something with a water activity of 0.90?
-Staphyococci such as S. aureus
-Brice Buryanek

6. Rank these liquids from lowest water activity to highest (honey, pure water, and human blood).
- Pure water, human blood, then honey
-Brandi Burke
This should be reverse because water have the activity of 1, blood is .995 and honey is .9 their for honey should be first in line
Hoa Le

7. An antiseptic is safe to use on the skin, and kills cells in a nonspecific way by targeting structures common to all cells such as Soap, Iodine, and Hydrogen Peroxide.
Disinfectants are used just on inanimate objects by destroying DNA, proteins, and phospholipid bilayer 1 example is Bleach.
Mackenzie D.

8. What are the difference between strict and facultative anaerobes?
The difference between strict and facultative anaerobes is that strict anaerobes are killed by the presences of oxygen. Facultative, however, can grow in oxygen rich environment but do not need it to grow.
A Permann

9. What is omotic pressure?
Pressure put on cells by H20 movement.
-Brandi Burke

10. List the factors that influence bacterial growth rates.
Factors are temp., ph, pressure, water activities, air condition, and competition with other micro.
-Hoa Le

11. Free radicals are electrons that are not attahenched to an atom. Free radicals are very destructive, they bounce around and damage the DNA and proteins which can the lead to mutations in DNA and even cell death.
Mackenzie D.

12. What is the difference between anaerobes and aerobes?
Anaerobes- bacteria live w/o oxygen
Aerobes- Bacteria live w/ oxygen
-Hoa Le

13. How much oxygen do microaerophiles need to grow?
Microaerophiles need approximately 5 percent oxygen air to grow.
A Permann

14. How much CO2 do capnophiles need to grow?
Capnophiles need 5-10 percent carbon dioxide in air to grow.

15. Is Strict or Facultative killed by oxygen?
Strict killed by oxygen
-Hoa Le

16. What is a hemocytometer? How does it work?
Hemocytometer are a slide that have a hold in the middle use to count bact.
-Hoa Le

Actually, a Hemocytometer is a slide with a grid (not a hold) in the middle used to count bacteria.
—Mackenzie D, Laci Swanson, Becky Lenhart, and Brandi Burke.

17. Why can't you see a virus using a light microscope?
b/c most virus are smaller than 2um.
-Hoa le

18. Advantages- Allows to see very small small items such as viruses, cell membrane layers, and ribosome shapes.
Disadvantages- Very labor intensive, specimens are dead and very expensive
Mackenzie D.

19. The squid has a light organ that houses Vibrio Fischeri. When the V. Fischeri live in such a high population they communicate and express different genes than a single V. Fischeri would. At the high density the V. Fischeri make Luciferase (light producing enzyme) which makes the squid glow.
Mackenzie D.

20. What is the difference between a Bright and Dark field microscopy?
Bright let you see the death bact. cell. Dark let you see movement of alive one.
-Hoa Le

21. Dark field microscopy allows you to see live and slender objects.
Mackenzie D

22. what is a hemocytometer? how does it work?

23. define generation time.
time that allow the bact to replicate.
-Hoa Le

24. What does it mean when something spoils?
when bact grow and replicate
-Hoa Le

25. why is the resolving power of an electron microscope so much smaller than that of a light microscope?
because electron are smaller then light wavelengh
-Hoa LE

26. why can't you see a virus using a light microscope?
bECAUSE VIRUS SMALLER THEN 2UM.
-hoa le

27. V. Fisheri are gram negative bacteria which are able to glow in the dark. If you see a bright glow in the agar tube the bacteria grow in, what does this mean? Choose all that apply.
a. the bacteria are growing at a high density
b. the bacteria are using quorum sensing to communicate
c. It's Halloween time
d. the bacteria are breaking down ATP to create energy to produce light
the answer are a and b
-Hoa Le

Actually, the answers are a,b, and c because the luciferase the bacteria produce break down the ATP to create the energy needed to produce the light.
—Laci Swanson, Brandi Burke, Mackenzie Dorsett, and Becky Lenhart

28. draw the bacterial growth curve, and include all the phages?

29. What do thermophiles and hyperthermophiles have in common? How are they different?
they both have saturated cell membrance and have more heat stable protein
diff. are thermophiles live at temp around 60-70c and hyper live at >100c.-Hoa Le

30. What are biofilms and how are they associated with Pseudomonas aeruginosa?.
Biofilms compose of lot of protein, lipid, and sugar codes. it increase ability of p. aeruginosa to cause disease.
-Hoa Le

31. What are some of the advantages and disadvantages of bright field microscopy and dark field microscopy?
adv. of bright field micoscopy are let you see what kind of bact (g+ or g-). It also let you see the shape. It take shorter time.
adv. of dark field microscopy are let you see movement of bact and slender structure. the disadv. are one can't have both adv. for example, bright field microscopy can't let you see movement of live bact.
-Hoa Le

32. What is Optical Density and how does a spectrophotometer work?

33. What does a hemocyometer do? And what are some characteristics of it?

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