Lecture 5 Flashcards Preview

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Flashcards in Lecture 5 Deck (98):
1

Each microbial species has a specific..

temperature range, above and below which the microbe cannot grow/survive

2

The temperature rang usually spans..

30 degrees C

3

Minimum temperature

lowest temp that can support growth of the microbe

4

Optimum temperature

preferred temp that best support the growth of microbe

5

Human body temp is usually

37 degrees C

6

Maximum temperature

highest temp supporting the growth of the microbe

7

5 groupings of bacteria based on their range of temperature

-psychrophiles
-psychrotrophs
-mesophiles
-thermophiles
-hyperthermophiles

8

Psychrophiles

cold loving, temp range supporting growth -5 to 15 C. Killed at 20 C. found in deep ocean and polar environment. no issues w/ food preservation

9

Psychrotrophs

bacteria w/in this group have very broad temp range 0 to 35 C. optimal temp 15 to 30 C. these microbes will cause food to spoil in fridge

10

Mesophiles

temp range 10 to 45C optical temp is 30 to 37C. alive in fridge but not growing

11

Most bacteria are what temperature range

mesophiles

12

Most pathogens (disease causing microbes) have an optimal temp of

37C

13

Thermophiles

temp range 45 to 70C. optimal temp 60C. cannot cause disease in human body

14

Hyperthermophiles

temp range 65 to 110C. bacteria in this group are limited to very few places on Earth were water reaches such high temp (deep ocean vents)

15

Heat is used to kill _____ and _____ living on food products (ex: cooking)

mesophiles and psychrotrophs

16

Cold temperature are used to.......

slow growth go microorganisms

17

What type of bacteria can grow in fridge

psychrotrophs

18

pH

measurement of acidity and alkalinity of substance

19

What pH allows cell to fold

7

20

Most bacteria grow at or around a ___ pH

neatural

21

Acidophiles

bacteria that grow at very low pH

22

Alkalophiles

bacteria that grow at very high pH

23

Neutrophiles

bacteria that grow at pH values between 5 and 8

24

Osmosis

movement go solvent molecules across a membrane or barrier of some sort

25

Water ALWAYS moves from an area of..

low concentration to and area of high concentration (up the concentration gradient)

26

Hypertonic solutions

solution is highly concentrated w/ solute

27

When cell is placed in hypertonic solution water will..

rush out of cell from low to high concentration, cell will shrivel or dry up

28

Hypotonic solution

solution has a low concentration of solute

29

When a cell is placed in hypotonic solution water will...

rush into cell from low to high concentration, cell will burst and be unfixable

30

Isotonic

when 2 solutions are of equal concentration, no result of net movement when placed into isotonic solution

31

Osmotic pressure is very important for

food preservation

32

Extreme halophiles

bacteria adapted to life at high salt concentration. bacteria live in dead sea (30% NaCl)

33

Blood salt concentration

0.9%, salt concentration too low to inhibit growth of most microorganism

34

Carbon

backbone of all living matter

35

Heterotrophs

obtain their carbon from organic matter, so unable to create their own (ex:proteins)

36

Autotrophs

obtain their carbon from inorganic mater (ex: CO2)

37

Nitrogen, sulfur, phosphorus, and iron

required in smaller amounts then carbon

38

Nitrogen for

nitrogenous bases, protein amino acids

39

Sulfur for

certain amino acids

40

Phosphorus for

nitrogenous bases and ATP

41

Iron for

ETC and hemoglobin

42

Trace elements

required in extremely small amounts, essential to the function of certain enzymes (ex: zinc)

43

Oxygen

only required by some organisms, can be extremely toxic to some organisms

44

5 classes of microorganisms based on oxygen use tolerance

-obligate aerobes
-facultative anaerobes
-obligate anaerobes
-microaerophiles
-aerotolerant anaerobes

45

Obligate aerobes

require oxygen for cellular respiration

46

Facultative anaerobes

can use oxygen for cellular respiration but can also grow well in anaerobic environments

47

Obligate anaerobes

cannot use oxygen for cellular respiration and are killed in presence of oxygen

48

Aerotolerant anaerobes

cannot use oxygen for cellular respiration but aren't killed in its presence

49

Microaerophiles

require oxygen in very low amounts and are killed by higher concentrations

50

Culture

microbes that are continuously growing and multiplying

51

Inoculum

microbes introduced into a culture

52

Batch culture

liquid media, once started there are no further nutrients added, once nutrients used up the bacteria begin to die

53

What is limiting component for batch culture

amount of nutrients

54

Continous culture

open system, nutrients are continually added. wastes are continuously removed

55

What type of system supports indefinite growth

Continous culture

56

Solid media

allows growth of colonies, contains all n nutrients required by the cells, contains agar

57

Colonies

densely packed groups of cells

58

Agar

solidifying agent, polysaccharide derived from marine algae, cannot be degraded by most bacteria

59

Solid media allows

isolation of pure cultures

60

For solid media one cell reproduces and eventually forms..

a huge population of cells which are genetically identical to one another

61

Culture medium

nutrients prepared for microbial growth, can be chemically defined or undefined

62

Cultire medium allows us to ..

grow pure bacterial cultures in lab

63

Prior to inoculation the media must be..

sterile, containing no living microbes

64

Chemically undefined media

contains unknown components, referred to as complex media

65

Example of chemically undefined media

media containing yeast extract, all of the soluble components come from crushed yeast cells

66

Chemically defined media

all of the media components are known, referred to as a minimal media

67

Example of chemically defined media

media containing known quantities of salts and sugars

68

Selective media

used to suppress the growth of unwanted organisms, promotes the growth of desired bacteria

69

Example of selective media..

bismuth sulfite agar used to culture salmonella typhi

70

Differential media

used to distinguish in between diff types of bacteria, all types of bacteria are able yo grow but colonies of certain bacteria look diff on the plate

71

Example of differential media...

blood agar plates used to culture streptococcus pygoenes and other bacteria that lyse and eat red blood cells

72

Example of agar both selective and differential

MacConkey agar

73

How MacConkey agar is selective

bile salts and dyes in the media inhibit the growth of most non intestinal bacteria, promoting the growth of bacteria that live in the intestine

74

How MacConkey agar is differential

lactose fermentation, lactose non-fermenters appear white

75

Lactose fermentation

bacteria that ferment lactose sugar produce acid products that turn pH indicator pink (E.coli)

76

Bacterial growth refers to an..

increase in bacterial cell number and not an increase in bacterial cell size, most bacteria reproduce by binary fission

77

First step in binary fission

bacterial cell elongates and makes identical duplicate of its chromosome

78

Second step in binary fission

bacterial cell containing two chromosomes continues to grow and a cross walk forms in between the two chromosomes

79

Third step in binary fission

the two cells separate and you have the original parent cell and a new genetically identical daughter cell

80

Generation time

measuring the growth of bacteria allows the calculations of the generation time of a particular organism

81

The generation time is the time it takes for...

a bacterial population

82

Generation time varies in between..

different bacteria

83

Most bacterias generation time is

between 1 - 3 hours

84

E.coli in rich media has extremely short generation time of

20 minutes

85

M. tuberculosis has a very slow generation of

24 hours

86

Since bacteria grow exponentially the bacterial growth curve is constructed using ..

log of the cell number

87

Lag phase

period of adaptation, cells adjusting to the new media and preparing for growth

88

Exponential phase (log)

cell numbers are increasing exponentially, period of maximal reproduction, used to calculate growth rate

89

Stationary phase

cells reached max population density, nutrients have been depleted, growth rate = death rate (no increase)

90

Death phase

all nutrients are exhausted, toxic waste products have accumulated, death rates exceed growth rate

91

2 primary ways that bacterial cells can be counted

-direct count
-viable count

92

Direct count

cells are counted using a light microscope, usually takes place in special counting chamber

93

Direct count is very inaccurate because..

it counts both live and dead cells

94

Viable count

only live cells are counted, liquid culture diluted, dilutions are plated onto agar plates, plates are incubated until the colonies grow

95

First step in counting bacteria

Each cell from the original dilute develops into a single colony

96

Second step in counting bacteria

number of colonies are then counted and can be used to determine the number of bacteria that were present in original sample

97

The counts are expressed as..

colony forming units per mL (cfu/mL)

98

The assumption is that 1 cfu =...

1 bacterial cell