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Micro Lecture > Chapter 6 Microbial Growth > Flashcards

Chapter 6 Microbial Growth Flashcards

1
Q

What is the definition of microbial growth?

A

It the increase in the number of cells not the cell size.

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2
Q

What do cells grow into?

A

Cells grow into a colony

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3
Q

What can understanding microbial growth do for us?

A

If we understand the conditions that are necessary for microbial growth, we can prevent disease and food spoilage.

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4
Q

What are the physical requirements for growth?

A

Temp

-pH

Osmotic

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5
Q

What are the chemical requirements for optimal microbial growth?

A 
Carbon
Nitrogen, sulfur, and phosphorous
Trace elements
Oxygen
Organic growth factor
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6
Q

How is temperature described in microbial growth?

A

Minimum growth temp

Optimal growth temp

Maximum growth temp

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7
Q

What are Psychrophiles/Psychrotrophs? What are their temperature ranges and what are they responsible for.?

A

Cold-loving

They grow in the refrigerator

Cause food spoilage

Psychrophiles grow below 20 C

Psychrotrophs- grow 0-30 degrees C

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8
Q

Describe Mesophiles optimal growth temp?

A

Moderate temp-loving

Because body temp is 37 C, pathogens belong to this group

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9
Q

Describe Thermophiles and their optimal growth temp?

A

They grow above temps 40 C and will not grow below 40 C.

Below 40 are called obligate thermophiles

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10
Q

What is the range of optimal grow for most bacterial in regards to food preservation?

What temp do many bacteria survive, and some may produce toxins

A

20-50 for rapid growth of microbes in food

5-15 C bacteria survive and many produce toxins

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11
Q

What are refrigerator temps and what takes place with growth?

A

0-15 C refrigerator temps which may allow slow growth of spoilage bacteria by very few pathogens

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12
Q

What happens to bacteria at temps within a freezer?

A

Under zero, no significant growth below freezing

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13
Q

What pH do most bacteria grow in?

A

6.5 to 7.5

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14
Q

What is the optimal pH that molds and yeasts grow in?

A

-pH 5 and 6

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15
Q

What pH is effective to keep bacteria from growing? What is a process that uses this pH?

A

Very few grow below pH 4. This pH is what is used to make yogurt, pickles, sauerkraut. And this prevents spoilage

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16
Q

What type of environment causes bacterial to lose water? And what takes place?

A

Hypertonic environments, or increase in salt or sugar will cause plasmolysis

The cell will lose water and the plasma membrane pulls away from the cell wall and causes death

This is bacterial osmotic pressure

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17
Q

What bacterial survive in areas that have high salt and have high osmotic pressure?

Who can tolerate these environments as well.

A

Extreme or obligate halophiles (salt loving) require high osmotic pressure

Facultative halophiles tolerate high osmotic pressure

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18
Q

How can bacteria tolerate Hypotonic (pure water)?

A

Because the plasma membrane rest on the rigid cell wall and prevents damage

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19
Q

What are the chemical requirements for bacterial growth?

A

Need a carbon source and an energy source

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20
Q

What the energy sources that are used for bacterial growth?

What do chemoheterotrophs and autotrophs use?

A

Energy source comes from carbohydrates, proteins and lipids.

Chemoheterotrophs use organic carbon sources

Autotrophs use CO2

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21
Q

What is another chemical requirements that comes from amino acid and proteins?

A

Nitrogen - comes from amino acids and proteins

Most bacteria decompose protein

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22
Q

What can N2 gas be used for and what bacteria uses it and for what?

A

N2 is use for nitrogen fixation

Rhizobium (symbiosis with plant roots)

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23
Q

Besides Nitrogen what other elements are used by bacteria for growth?

A

Sulfur and Phosphorus

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24
Q

What sulfur and phosphorus compounds are used?

Where are these compounds found?

A

Sulfur is present in come AA

Phosphorus is in DNA, RNA, and ATP and membranes

Some bacterial use SO4 2- (sulfate) or H2S (rotten egg gas)

PO4 3- is a phosphate ion and a source of phosphorus

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25
Q

What are trace elements?

A

These are inorganic elements that are required in small amounts to help enzymes function.

Fe (iron), Cu (copper), Zn (Zinc) these are enzyme cofactors

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26
Q

What is the effect of 02 on growth?

A

Even though we need it O2, its a poisonous gas

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27
Q

What type of bacteria need O2 to grow?

A

Obligate aerobes need O2 to grow

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28
Q

What bacteria can grow in the presence of O2 but can live without it?

What type of environment causes this growth without O2 present

A

Facultative anaerobes: use O2 when present but can live without it.

Without its fermentation or anaerobic respiration. E. coli

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29
Q

What type of bacteria lives without the presence of O2?

A

Obligate anaerobes: can only live in the absence of O2

O2 is toxic to these bacteria because they don’t have SOD and Catalase enzymes.

SOD breaks down superoxide radicals to O2 and peroxide. Catalase breaks down peroxide to water and oxygen

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30
Q

What is an example of an obliged anaerobes?

A

Clostridium which cause tetanus and botulism

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31
Q

What are Aerotolerant anaerobes?

A

Do not need O2 but can tolerate it

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32
Q

What microbes use O2 but need less of it to survive.

A

Microaerophiles: they are aerobic but need less concentration of O2 because they produce a large amount of toxic material in the presence of O2.

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33
Q

What are the forms of toxic oxygen?

A

Singlet oxygen: these are vey reactive and found in phagocytic cells

Superoxide free radicals (O2-) is very toxic found in obligate anaerobes

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34
Q

What enzyme neutralizes superoxide free radicals

A

SOD Superoxide dismutase

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35
Q

What enzyme neutralizes peroxide anion and generates O2, which one does not produce O2?

A

Catalase produces O2

Peroxidase does not generate O2

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36
Q

What is the most reactive molecule, this is also one of the body’s best defenses agains pathogens?

A

Hydroxyl radical

Very reactive molecule

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37
Q

Where are Organic growth factors found?

What is a key feature about them and our body?

A

Organic compounds obtained from the environment

They are vitamins, amino acids, purines, and Pyrimidines

These are essential and found in our environment. We are unable to synthesize them.

38
Q

Bacteria seldom live individually. Where do you find bacteria? What type of community?

A

Microorganisms live in communities called Biofilms

39
Q

What are Biofilms?

A

They are a thin slimy layer that encase bacteria, which allow them to adhere to surfaces easier

40
Q

What are Biofilms composed of, and what do they form?

A

Made of polysaccharides and they form slime or hydrogels

they are found on the surface of a rock or the human tooth

41
Q

What is distinct trait about a biofilm community?

A

Their function within the community are usually coordinated together. They are able to coordinate their activity as a group

42
Q

How do bacteria within a biofilm communicate?

A

Use cell-to-cell communication called Quorum sensing

43
Q

What are the benefits of a biofilm?

A

They can share nutrients

They are sheltered from harmful factors like desiccation and antibiotics

Also allows for the share of genetic information through conjugation

44
Q

What problems do Biofilms cause humans?

A

They are a factor in human disease

They cause nosocomial infections that are acquired in hospitals: like on a catheters

45
Q

What is lactoferrin? What does it do?

A

Found in human secretions (milk) and inhibits biofilm formation

46
Q

What was found on the catheters in hospitals after it was grown for several days?

A

Pseudomonas fluorescens was cultured form the catheters

47
Q

What is culture medium?

A

Nutrients prepared for microbial growth

48
Q

What does sterile mean?

A

No living microbes

49
Q

What is the difference between inoculated and contamination?

A

Inoculum: Intentionally introducing microbes into a medium

Contamination: undesirable bacterial presence

50
Q

What is a culture?

A

It’s the microbes that grow in or on a culture medium

51
Q

What is Agar?

What is it made of?

A

It’s a complex polysaccharide that is used as a solidifying agent for culture media in Petri plates, slants and deeps

Not metabolized by microbes

52
Q

Why is agar being used and what was originally use and why did we stop using it?

A

Used to use gelatin, but some bacteria could utilize it

53
Q

What are its working temps?

A

Agars liquid temp is: 100 C

It Solidifies at ~40 C

54
Q

What is chemically defined media and complex media?

A

Chemically defined media: exact chemical composition is known

Complex media: extracts and digest of yeasts, meat, or plants

55
Q

What are examples of Complex media?

A

Nutrient Broth

Nutrient Agar

56
Q

What type of media does Anaerobic microbes need?

A

Reducing media

57
Q

What types of culture methods does anaerobic microbes need to grow?

A

Reducing media

58
Q

What is reducing media?

A

Contains chemicals like thioglycolate or oxyrase that combine to with dissolved O2 to deplete it

They are then heated to drive off the O2

59
Q

What are some things used to remove O2

A

Anaerobic Jar, Anaerobic Chamber, and capnophiles.

60
Q

What are Capnophiles?

A

Microbes that require high CO2 conditions

These conditions can come from CO2 packets or a candle jar

61
Q

What is selective media?

A

This media suppress unwanted microbes and encourage desired microbes

62
Q

What is Differential Media?

A

Bacterial colonies that show distinctive appearance on different media

A way to distinguish specific organism based on the media being used.

Ex MSA S.aureus like the high salt environment

Makes it easy to distinguish colonies of different microbes

63
Q

What is Enrichment Culture used for?

A

Encourages growth of desired microbe that is in small numbers. This will help produce enough of the bacteria to form a colony

This is often used on soil and fecal samples.

64
Q

What is colony? Which comes from what?

A

A colony is a population of cells arising from a single cell or spore or from a group of attached cells.

A pure culture contains only one species or strain

65
Q

What is the method used to isolate pure cultures?

A

The streak plate method

66
Q

What are two other methods used for isolation of a pure culture?

A

Pour Plate and spread plate method

67
Q

How do prokaryotes reproduce? What are the different methods?

A

Divide by binary fission, budding, and some by Conidiospores, some by fragmentation of filaments

68
Q

What are the steps of Binary Fission?

A

Cell elongates and DNA is replicated.

Cell wall and plasma membrane begin to constrict

Cross-wall forms, completely separating the two DNA copies

Cells separate

69
Q

What does the number that is the exponent or power of 2 show in bacterial generation?

A

When the number of cells is expresses as a power of 2, then the exponent show the number of generation

2^0 = 1 initial number of cells
2^1 = 2 number of cells after the first generation
2^2 = 4 number of cells after 2 generations
2^3 = 8 number of cells after 3 generations
70
Q

What is doubling time?

A

The time required for bacterial cells to divide or double in number

71
Q

Using standard numbers to define the total number of bacterial that has divided is way to big. What is used in its place?

A

Use a logarithmic scale

72
Q

What is the difference between logarithmic and arithmetic graphs when graphing cellular growth?

A

Arithmetic plot Dow not shoe the population changes in the early stage of growth

When the growth began to show it would run off the page.

You are able to graph a best fit line using a logarithmic scale.

73
Q

What are the 4 phases of Bacterial Growth?

A

Lag Phase

Log (exponential) phase

Stationary phase

Death phase

74
Q

Explain the Lag phase. What takes place?

A

There are no visible changes in the number of cells. The is a period of adaptation

This is the period of preparation for growth but no growth

75
Q

What is the log (exponential) phase

A

The sharp increase in the number of cells. It’s a straight line. The generation time is constant.

The cells begin to divide. Reproduction is the most active in this phase

76
Q

What is the stationary phase?

A

Growth starts to slow does

The number of microbial deaths balances the number of new cells formed.

77
Q

What is one of the reasoned cell deaths balances the number of new cells in the Stationary phase?

What is another name for the Stationary phase?

A

The is due to the exhaustion of nutrients, accumulation of toxic wastes and changes in pH.

This can be referred to as a period of equilibrium.

78
Q

What is the Death phase?

A

Number of deaths exceeds the number of new cells ( also called the logarithmic decline phase)

79
Q

How can we measure growth? Meaning what is measured?

What are the counts that are used to make this measurement?

A

We can measure the

Cell number and the population total mass

It’s measured either by Viable count: which is the total number of living cells, or by non-viable: which is total cells, either dead or alive.

80
Q

What are the methods users to measure viable counts and which one is more accurate?

A

The pour plate method and the spread plate method.

Spread plate method is better to use.

Also use serial dilutions

81
Q

Why can’t you plate from the first mixture? Meaning no serial dilutions?

A

Because when plating it there would be a lawn of growth. You are unable to accurately count them.

82
Q

What is the range to be able to count bacteria?

A

You want to count colonies on a plate that have 25-250 CFU’s

Some microbiologist say 30-300 CFU’s

83
Q

When is counting bacteria by membrane filtration used?

A

Used when the number of bacteria is low and when working with water from lakes and rivers. The filter catches the bacteria.

84
Q

What are the drawbacks to using the pour plate method?

A

The agar is at a high temp and some bacteria are unable to handle the 100 C and therefore die. Also the bacteria that form in the Agar could also cause a problem.

85
Q

What is use when bacteria won’t grow on or in solid media?

A

MPN. Most probable number

This is statistical estimate. Nothing more than a statement of how many bacteria is estimated to fall within a certain number.

86
Q

What bacteria is MPN primarily used with?

A

Most useful to detect coliform (enteric) bacteria that ferment lactose in differential media

It is used in water testing. Lakes and rivers.

87
Q

When is Direct Microscopic Count done?

A

Example is when counting bacteria in milk. Time is an issue and must be done quickly, therefore this method is done.

A sample is spread over a slide that is designed to have the area graphed out in the viewing area so that one can count the number of bacteria in them.

88
Q

What are some disadvantages to Direct count method?

What is an advantage of this method?

A

Motile cells are hard to count.

Dead cells are counted as live ones giving false results.

Advantage is that no incubation time is needed.

89
Q

What are the direct methods to measuring microbial growth?

A

Plate counts

Filtration

MPN

Direct microscopic count

90
Q

What are the indirect methods for measuring microbial growth?

A

Turbidity

Metabolic activity

Dry weight: for filamentous organisms

91
Q

What is turbidity and how is it used to measure microbial counts?

A

You use a spectrophotometer to measure the turbidity or microbial growth in a sample.

As the number of bacteria grow an increase in turbidity will take place.

As this number of bacteria changes the percent transmission will change indicating a higher count.

You then use absorbance to plot the amount of bacteria

Micro Lecture (11 decks)

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