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Micro Exam 1 (Lauren) > Bacterial Morphology And Growth > Flashcards

Bacterial Morphology And Growth Flashcards

1
Q

What is happening during the death/decline phase?

A

There are insufficient resources for cell growth, so the bacteria begin dying exponentially. However, they’re dying at a rate slower than the rate they multiplied during the log phase.

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2
Q

Are endospores part of the reproductive cycle of bacteria?

A

No**

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3
Q

Can you use OD or biomass to measure the amount of bacteria during the death/decline phase?

A

No, only CFU

OD and biomass can not differentiate between dead or living cells

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4
Q

What are the 2 clinically important acid-fast organisms you need to know?

A

Mycobacterium tuberculosis

Nocardia asteroides

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5
Q

What does the keratin coat of endospores do?

A

Impervious to many chemicals, and the immune system can’t see it

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6
Q

What are the 5 phases of bacterial growth?

A

Lag phase

Log phase

Late Log phase

Stationary phase

Death/decline phase

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7
Q

What are the 3 antigens we discussed and where are they located?

A

O antigen: LPS in Gram negative outer membranes

H antigen: filament part of flagellum

K antigen: glycocalyx

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8
Q

What is the first step of identifying an organism?

A

Isolating it in pure culture.

Usually done by streaking plates with a wire loop

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9
Q

What are the 2 most common bacterial shapes?

A

Coccus

Bacillus

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10
Q

What is selective media?

A

Media that inhibits the growth of certain unwanted organisms (ex: has an antibiotic in it)
Only certain organisms will be able to grow

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11
Q

What are the 3 areas of bacterial taxonomy?

A

Classification- grouping them by certain properties

Nomenclature= naming it

Identification- using a classification scheme to isolate and identify organisms

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12
Q

Is there population growth during the stationary phase of bacterial growth?

A

NO

Even though they are dividing, they are dying at the same rate (and eating the dead bacteria to make new ones)

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13
Q

What is happening during the stationary phase?

A

Supplies of energy and nutrients have been exhausted

Resources are renewed by cell death (peptides and nucleic acids released)

Death is equal to division**

NO CHANGE in CFU/mL, OD, or Biomass

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14
Q

What does diplo- mean?

A

Paired bacteria

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15
Q

How long can endospores last in the environment/

A

Months to years

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16
Q

What are the features of common pili/fimbriae?

A
  • composed of pilin subunits
  • tips have adhesins/lectins that bind to sugars
  • arranged in a peritrichous arrangement (all over the surface like hair) that function in adhesion and a “twitching” motility
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17
Q

What is the name of the stain used that gram negative organisms retain?

A

Safranin

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18
Q

What are the 3 major components of the flagellum?

A

Filament- spins to propel the bacteria (H Antigen is here)

Hook- attaches filament to basal body

Basal body- anchors into cell wall and membrane

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19
Q

What is a common trigger of endospore formation?

A

Nutrient depletion.

When conditions get better, the endospore will germinate and produce one cell

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20
Q

True or false:

Many pathogens are capnophilic?

A

True!

Neisseria

Haemophilus

Helicobacter

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21
Q

What does minimum, optimum, and maximum values mean when it comes to particular environmental parameters that support the growth of a microbe?

A

Minimum: minimum value (pH, temp, oxygen, etc) that supports growth of microbe

Maximum: maximum value that the organism can tolerate (DOES NOT MEAN MAXIMUM GROWTH!!!)

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22
Q

How does biomass work to measure bacteria?

A

Your sample is washed, dried, and weighed.

This measures viable AND non-viable cells

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23
Q

What is an example of a fastidious organism that requires enriched media?

A

Haemophilus/Neisseria

Requires hemin and NAD for growth, so they will not grow on blood agar, only on chocolate agar

(I don’t know if this is important)

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24
Q

If you put an obligate anaerobe into liquid in a test tube, where will it grow?

A

At the bottom

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25
Q

What are the 3 classifications for bacteria types regarding their pH preferences?

A

Acidophiles

Neutrophiles (most pathogens)

Alkaliphiles

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26
Q

What two stains are used to stain acid fast organisms?

A

Primary stain: carbol fuschin

Counterstain: methylene blue

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27
Q

What is a function of many inclusions/inclusion bodies?

A

Storage depots (collections of nutrients etc so it can divide at a moment’s notice)

Ex:
Volutin granules- polymers of phosphate

Glycogen granules

PHB granules- chains of B-hydroxybutyric acid

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28
Q

Does differential media select for specific organisms/inhibit growth of certain ones?

A

No

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29
Q

What are the 2 clinically relevant genera of bacteria that produce endospore?

A

Bacillus

Clostridium

(Both are gram positive, but the location and size of the spore differs among the different species, so it can help you identify the bacteria)

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30
Q

Where is the periplasmic space and what is in it?

A

Between the outer membrane and the inner membrane

Contains peptidoglycan, transport proteins, and HYDROLYTIC ENZYMES

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31
Q

What are the 3 components of the outer membrane in gram negative cells?

A

LPS (most of the outer part of outer membrane)

Trimeric Porins

Lipoprotein

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32
Q

How does the colony forming unit (CFU) test work to measure bacteria?

A

You dilute a culture, smear it on a plate, then count the number of colonies that grow. Each colony came from 1 cell.

This will measure ONLY viable cells

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33
Q

What are the 3 ways we can measure bacterial growth?

A

Optical Density

Colony Forming Units- only one that measures viable cells

Biomass

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34
Q

Where is the peptidoglycan in gram negative bacteria?

A

In the periplasmic space

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35
Q

What are plasmids?

A

Other bits of dna outside the main chromosome that contain ancillary information (not essential for cell survival)
Ex: antibiotics, antibiotic resistance, heavy metal resistance, toxins, etc. things that increase its virulence

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36
Q

If you have a mixed infection, how do you isolate a single organism?

A

You first need to streak the sample onto a plate by doing 3 streak series, diluting the number of cells each time. (See slide 66)
Once those colonies grow, they will be far enough apart to see the different types. Pick a colony of the organism you want, and streak it on a new plate to make a pure culture.

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37
Q

What are halophiles?

A

Bacterita that require high salt

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38
Q

What does Lipid A do?

A

It is a heat-stable endotoxin embedded in the outer membrane of gram negative cells.

When the cell is lysed, it gets released and makes your immune system go berserk. It is a B cell nitrogen, and induces cytokines and inflammatory mediators.
~~responsible for bacterial sepsis!

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39
Q

In what 2 ways do LTAs and WTAs increase the virulence of gram positive organisms?

A
  1. Function as adhesins- they are sticky and adhere to host cells to begin invasion
  2. Initiate endotoxin-like activities when released (along with peptidoglycan)
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40
Q

What does the core polysaccharide do?

A

It connects the O antigen to Lipid A

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41
Q

What does the O antigen do?

A

Its a sticky sugar that attaches to host cells (inhibits phagocytosis)

It is also highly variable and immunogenic, used to identify bacterial strains

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42
Q

In peptidoglycan, you have chains of NAM and NAG that are cross linked by tetrapeptides. Which disaccharide do the tetrapeptides hang off of?

A

NAM

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43
Q

What kind of proteins are embedded in the mycolic acid layer of acid-fast cell walls?

A

Tetrameric porins

Gram negative had TRImeric

44
Q

What is complex/undefined media?

A

Media where we don’t know the EXACT composition.

Ex: yeast extract media or potato extract agar

45
Q

What happens when its too hot for bacteria?

A

Denaturing structural proteins

Denaturing enzymes

46
Q

What two structures are in the peptidoglycan layer of gram positive cells that increase their virulence?

A

Wall teichoic acids WTA (anchored to peptidoglycan)

Lipoteichoic acids LTA (anchored to cell membrane)

47
Q

Which is more expensive:

Defined media or complex media

A

Defined

48
Q

What does sarcina mean?

A

A packet of 8 cells

49
Q

What is the difference between obligate and facultative?

A

Obligate: no alternative

Facultative: has alternatives and can survive in different conditions

50
Q

What are osmophiles?

A

Bacteria that require high osmolarity/sugar

51
Q

What is a glycocalyx?

A

The “sugar coating” outside the cell wall. May be a capsule or a slime layer.

It is a virulence factor that helps the bacteria:
Avoid dessication
Acts as a barrier from toxic molecules
Inhibits phagocytosis
Promotes adherence to cells/surfaces
Induces abscess formation 
Decreases complement-mediated lysis
52
Q

What is happening during the log phase of bacterial growth?

A

Exponential growth and rapid cell division

Bacteria are producing metabolites and virulence factors

53
Q

What are microaerophiles?

A

Bacteria that require oxygen, but at lower levels than obligate/strict aerobes

54
Q

How does optical density work to measure bacterial growth?

A

You measure how much light the cloudy tube of bacteria absorbs and you can find out how many are in there.

Measures viable AND non-viable cells (dead cells still absorb light)

55
Q

Which has a narrower range of growth: defined media or complex media

A

Defined

56
Q

Obviously, acid-fast bacteria do not stain with Gram stain. Does that mean that they don’t have any peptidoglycan?

A

No, they do have peptidoglycan, but it has a waxy coating that repels the stain

57
Q

What is happening during the late log phase?

A

They are starting to run out of nutrients and space to grow, so they start producing secondary metabolites like antibiotics and pigments to kill off competition

58
Q

What does strepto- mean?

A

Bacteria are in a chain

59
Q

What is happening during the lag phase of bacterial growth?

A

The bacteria are increasing their biomass, but not dividing.

They’re getting ready to divide

60
Q

What kind of ribosomes do bacteria have?

A

70S (30S + 50S subunits)

Different than human ribosomes

Transcription and translation are coupled

61
Q

What are the 3 enzymes that bacteria can make to counteract reactive oxygen species?

A

Superoxide dismutase

Catalase

Peroxidase

62
Q

What does the length of the lag phase depend on?

A

Availability of nutrients

Condition of inoculum

63
Q

What is differential media?

A

Media that differentiates between organisms.

It has components that will result in a visible change if certain bacteria grow on it. (Ex: color change)

64
Q

What does lipoprotein do?

A

Anchors the outer membrane to the peptidoglycan layer (gram negative cells)

65
Q

What are the 2 types of pili?

A

Common pili/fimbriae

Sex pili

66
Q

If you put a facultative anaerobe into liquid in a test tube, where will it grow?

A

All throughout the liquid (Top, bottom, middle )

67
Q

What is the only kind of bacteria that does NOT have enzymes for reactive oxygen species?

A

Obligate/strict anaerobes

Oxygen will kill them

68
Q

What do pili do?

A

They are little hairs with adhesins at the tips that help the bacteria adhere to each other or to host cells

69
Q

How do bacteria replicate?

A

Binary fission

1 bacteria replicates its DNA and gets bigger, then it separates into 2 genetically identical bacteria

70
Q

Will antibiotics that inhibit cell wall synthesis work on cells that are not actively growing/

A

No

71
Q

What are capnophiles?

A

Bacteria that require high CO2 levels (3-5%)

72
Q

What does staphylo- mean?

A

Grapelike cluster

73
Q

What is enriched media and what is the benefit of it?

A

It is complex media that has growth factors added to it.

Used for growing fastidious organisms (finicky)

74
Q

Do facultative aerobes/anaerobes require oxygen?

A

No, but they will use it if it’s available

They also have enzymes for reactive oxygen species

75
Q

How do you grow capnophiles in the lab?

A

Candle jars, CO2 packets, automated systems

76
Q

What does pleomorphic mean?

A

No defined shape

77
Q

What is the difference between an obligate anaerobe and an aerotolerant anaerobe?

A

The aerotolerant anaerobe has enzymes to detoxify reactive oxygen species

The obligate/strict anaerobe does not have these enzymes, so oxygen is toxic to them.

78
Q

What kind of media is required to grow fastidious organisms?

A

Enriched media

You won’t find them if you try to use anything else

79
Q

Where is the H antigen located?

A

In the filament portion of the flagellum

80
Q

Which two proteins are found in the outer membrane of gram negative cells? (Not in the LPS part)

A

Trimeric protein channels/porins

Lipoproteins (most abundant protein in gram negative cells)

81
Q

What kinds of bacteria are resistant to dessication?

A

Spore forming (bacillus and clostridium)

Cell wall modification (mycobacterium and their mycolic acids)

82
Q

Most pathogenic bacteria are _________

A

Mesophiles

83
Q

Is the cell wall internal or external to the cell membrane?

A

External

84
Q

What part of the gram negative bacteria is responsible for bacterial sepsis?

A

Lipid A

(It directly activates the alternative complement pathway, and then casues the release of cytokines and other inflammatory mediators)

85
Q

What kind of bacteria can grow on MacConkey agar?

A

Gram negative ONLY

Would be good for enteric infections, since most of those are Gram -

86
Q

What are mesophiles?

A

Bacteria that can live in temperatures from 12-42°C, but LOVE living from 30-37°C
(Body temperature)

87
Q

Does the bacterial cell membrane contain sterols?

A

No

Some exceptions

88
Q

Where is the K antigen?

A

In the glycocalyx

89
Q

What does tetrads mean?

A

Packets of 4 bacterial cells

90
Q

What are 2 ways that organisms can interfere with peptidoglycan to try to kill bacteria? (Not human made antibiotics)

A
  1. Secreting antimicrobial compounds

2. Secretion of lysozyme

91
Q

What are inclusion bodies?

A

Collective term for granules, vesicles and vacuoles within the cytoplasm

92
Q

How does lysozyme work to interfere with peptidoglycan?

A

Degrades the glycan backbone to weaken the integrity of the cell wall EVEN IN bacteria that are NOT actively growing

93
Q

What are endospores?

A

Resting stage of bacteria that contains:
1 chromosome
Small amounts of proteins and ribosomes
Peptidoglycan
High concentration of calcium bound to dipicolinic acid*
Keratin spore coat** (not noticeable to immune system)

94
Q

Do bacteria have a defined nucleus?

A

No they have a nuclear region/nucleotide with a single circular chromosome

95
Q

If you put an obligate aerobe into liquid in a test tube, where will it grow?

A

At the surface

96
Q

What is the name of the stain used that gram-positive organisms retain?

A

Crystal violet

97
Q

What is defined media?

A

It has known quantities of each component (carbon, nitrogen, etc)

98
Q

What is the difference in glycocalyx types: capsule vs slime layer?

A

Capsule: rigid shell that closely surrounds the cell

Slime layer: loose, non-uniform, diffuse

99
Q

How does the mycolic acid layer of acid fast cells help them?

A

It gives the organism a waxy coat that functions to resist dessication, antibiotics, and phagocytosis.
(It “hides” the bacteria from the immune system and it can take as long as it wants to grow)

100
Q

Where are trimeric protein channels (porins) located and what do they do?

A

They are in the outer membrane of gram neg cells (not the LPS part)

They are nonspecific channels that let water and small molecules across the membrane

101
Q

What does a sex pili do?

A

Adheres two cells together to allow for conjugation aka the exchange of DNA

102
Q

What kind of media is MacConkey Agar?

A

Differential AND Selective

It has bile salts and crystal violet that inhibit Gram positive bacteria from growing

It also has “neutral red,” a pH indicator that will change color if the bacteria that grows can ferment LACTOSE or not

103
Q

What happens to bacteria when it’s too cold for them

A

Loss of enzyme activity

Decreased membrane fluidity

104
Q

What are the 3 parts of the LPS in order from external to internal?

A

O antigen

Core polysaccharide

Lipid A

105
Q

Where is the periplasmic space located?

A

In between the inner and outer membranes of gram negative bacteria

106
Q

What does the calcium dipicolinate in endospores do?

A

Heat resistance

Micro Exam 1 (Lauren) (7 decks)

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