Chapter 6

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Microbiology
Chapter 6
Microbial Growth
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1

What is an orderly and permanent increase in the mass of protoplasm of an organism or population?

Growth

2

What is "orderly" growth?

A proportionate increase in all constituents

3

What is microbial growth?

An increase in the number of cells, not cell size

4

What is an increase in the number of individuals and can be independent of growth?

Reproduction: cells may grow without reproducing or may reproduce without growth

5

The lowest temperature where growth occurs?

Minimum temperature

6

The best temperature where growth occurs?

Optimum temperature

7

The highest temperature where growth occurs?

Maximum temperature

8

Which organisms are "cold-loving" with a growth temperature of 0 to 20 degrees Celsius and an optimum growth at 15 degrees Celsius?

Psychrophiles

9

What are mesophiles?

Organisms that are "middle-loving" and grow at 20 to 45 degrees Celsius and have optimum growth at 20 to 37 degrees Celsius.

10

Which organisms are "heat-loving" and grow at 37 to 65 degrees Celsius?

Thermophiles

11

Most bacteria grow in what range of pH?

6.5 to 7.5 (same as human levels)

12

What is the optimum pH for acidophiles?

0 to 5.5

13

What is the optimum pH for basophiles?

8.5 to 11.5

14

What can cause organisms to change the culture media to toxic due to pH change?

Their own waste products (generally acidic)

15

Which environment increases salt or sugar, cause plasmolysis?

Hypertonic

16

Which type of halophiles REQUIRE high osmotic pressure?

Extreme or obligate halophiles

17

Which type of halophiles TOLERATE high osmotic pressure?

Facultative

18

What are the environmental factors impacting growth?

Temperature, pH, osmotic pressure and chemicals

19

True or False: Obligate aerobes can live without oxygen.

False

20

Facultative anaerobes can grow...

with or without oxygen

21

Obligate anaerobes...

cannot live with oxygen

22

Aerotolerant anaerobes...

tolerate oxygen

23

Microaerophiles

need less oxygen and more carbon dioxide

24

When oxygen becomes toxic an enzyme is needed to convert the very toxic, free radical to get rid of hydrogen peroxide. Explain which enzyme is used to remove peroxide

superoxide dismutase removes H2O2 to make H20 AND O2

catalase removes H2O2 to make 2 H20 AND O2

peroxidase removes H202 to make 2 H2O

*PEROXISOME makes and gets rid of H2O2

25

What are the chemical requirements for growth?

Carbon, nitrogen, sulfur and phosphorus

26

Cells are what percentage water?

80 to 90%

27

What are trace elements and name them?

Inorganic elements required in small amounts and usually enzyme cofactors - Iron, manganese, magnesium and vitamins

28

What is an example of an autotroph? Why?

Plants - they use CO2 but they can make it for themselves

29

What is a chemoheterotroph?

Organisms that use organic carbon sources; such as humans and fungi.

30

Which chemicals can be limiting factors in growth?

Nitrogen, sulfur and phosphorus (NSP to remember)

31

Most organisms can produce more energy when growing in oxygen but what are the risks?

Toxic byproducts of oxygen can be fatal to cells

32

What must aerobes, faculative anaerobes and aerotolerant have in order to deal with toxic byproducts?

superoxide dismutase, catalase and peroxidase

33

Obligate aerobes...

cannot live WITHOUT oxygen (O2)

34

Faculative anaerobes...

Can live WITH orWITHOUT oxygen

35

Obligate anaerobes...

cannot live WITH oxygen

36

Aerotolerant anaerobes...

TOLERATE oxygen

37

Microaerophiles...

Require oxygen but can only grow at low oxygen tension - they need less oxygen and more CO2

38

What are toxic forms of oxygen?

Singlet oxygen: O2 boosted to a higher-energy state, extremely reactive

Superoxide free radicals: O2- (VERY TOXIC)

Peroxide anion (O2)2-

39

Which enzyme gets rid of superoxide free radicals?

superoxide dismutase

40

Which enzyme(s) gets rid of peroxide anion?

catalase and peroxidase

41

What is inoculum?

The introduction of microbes into a medium

42

What is a culture?

Microbes growing in/on culture medium.

43

What is a culture medium?

Nutrients prepared for microbial growth.

44

What does sterile mean?

No living microbes

45

What is a pure culture?

A culture coming from an isolated colony on a plate containing only one colony type

46

In what type of culture are most microorganisms found?

mixed culture

47

What is a synthetic or defined medium?

A medium made of known amounts of chemicals

48

What is a complex medium?

A medium made of some ingredients are of unknown composition or amount (extracts of plants, yeast or meat). Examples would be: nutrient broth or tryptic soy broth

49

What is agar?

A solidifying agent for culture media in Petri plates, slants and deeps. A complex polysaccharide made from red algae. It is generally not metabolized by microbes (microbes cannot degrade it so it remains solid). However, it liquefies at 100C and solidifies at -40C.

50

What percentage of agar is used for a solid media?

1.5%

51

What percentage of agar is used for a semi-solid media and why are semi-solid media used?

0.5% and it is used for motility studies

52

What percentage of agar is used for liquid media?

0 (no agar)

53

What is blood agar?

a differential medium containing red blood cells

54

What is MacConkey agar?

a specialized bacterial growth medium that is selective for Gram-negative bacteria and can differentiate those Gram- bacteria that are able to ferment lactose.

55

What is a selective medium?

A medium that encourages the growth of certain organisms while discouraging the growth of others

56

What is a differential medium?

A medium that distinguishes between different groups of bacteria

57

What is generation time?

The time required for cells to divide (and thus double the population), can be as short as 20 minutes or longer than a day.

58

If a single bacterium reproduced every 30 minutes, how many would there be in 2 hours?

16

1_2_4_8_16

59
card image

What are the phases of the growth curve?

1. Lag

2. Log

3. Stationary

4. Death

60

Describe the lag phase.

The period of little or no cell division but the cells are not dormant. There is intense metabolic activity involving synthesis of enzymes and various molecules.

61

What is the log phase?

Or the exponential growth phase, cellular reproduction is most active and the generation time reaches a constant minimum

62

Describe the stationary phase.

Eventually, the growth rate slows, the number of microbial deaths balances the number of new cells and the population stabilizes - a period of equilibrium.

63

What is the death phase?

When the number of deaths exceeds the number of new cells formed and continues until the population is diminished to a tiny fraction of the number of cells in the previous phase or until the population dies out entirely.

64

What are direct methods of measuring growth?

Plate counts (serial dilution; filtration, MPN (most probable number; statistical method); direct microscopic count

65

What are indirect methods of measuring growth?

Increase in turbidity with time

metabolic products

dry weight

66

What is the main difference between direct and indirect measurements of growth?

In direct we only measure live bacteria