Exam 2 Flashcards

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1
Q

Cytoplasm

A

The substance inside the plasma membrane
80% water plus carbohydrates, lipids, ions, and proteins (CLIP)
Cytoskeleton in cytoplasm; gives a cell its shape

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2
Q

Which of the following is common to all bacterial species?

A

Ribosomes, Plasma Membrane

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3
Q

Which of the following is the primary distinction (defining characteristic) between prokaryotic and eukaryotic cells?

A

Presence vs absence of a nucleus

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4
Q

In bacteria, the ribosomes subunits are:

A

30S, 50S

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5
Q

A compound that is transported through a membrane by a transporter protein without energy expenditure is called:

A

Facilitated diffusion

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6
Q

What part of the bacterial cell is targeted by beta-lactam antibiotics?

A

cell wall

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7
Q

Fluorescent

A

Some molecules have the ability to absorb light at one wavelength and emit at a different wavelength

These molecules are engineered into bacteria to aid in detection

Fluorescence microscopy: green squiggly lines

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8
Q

What is the defining difference between prokaryotic and eukaryotic cells?

A

Eukaryotes have a nucleus with DNA, prokaryotes don’t have a nucleus

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9
Q

Which of the following are examples of an anabolic process?

A

DNA replication, Transcription, Translation

Why: builds DNA, RNA, and protein(s)

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10
Q

Which of the following is found in/at the active site of an enzyme?

A

Competitive inhibitor, substrate(s), product(s)

Why: products are present at the active site, even if it’s just momentarily

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11
Q

Which of the following is involved in both cellular respiration and fermentation?

A

Glycolysis

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12
Q

Carbohydrate fermentation tests contain a _________that will change color to signify that fermentation has occurred

A

pH indicator

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13
Q

Why does enzyme activity decrease as temperature decreases?

A

Fewer interactions between substrate and enzyme

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14
Q

Which of the following statements most accurately describes the movement of water when a cell is placed in an environment with low solute concentration (e.g. pure water)?

A

Water diffuses into the cell due to the hypotonic environment, causing the cell to rupture

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15
Q

In the lab, you are inoculating a culture when you:

A

Transfer some bacteria into media

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16
Q

An experiment began with 5 bacterial cells and ended with 40 cells. How many generations did the cells go through?

A

3

Why: Start with 5 → 1 double = 10 → 2nd double = 20 (10 x 2) → 3rd double = 40 (20 x 2)

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17
Q

Which of the following statements about oxygen are true?

A

Oxygen is required by some bacteria (obligate aerobes)

Oxygen is toxic to some bacteria (anaerobes)

Some bacteria use oxygen as the final electron acceptor during cellular respiration

Some bacteria can break down oxygen and reactive oxygen species using enzymes

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18
Q

Which of the following approaches is based on probability/statistics and used for estimating bacterial counts for water safety?

A

Most Probable Number

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19
Q

Complex Media

A

Most often used

Supports the growth of many types of bacteria

Contains ingredients like yeast extract, meat extract, and protein digests

Chemical composition of ingredients isn’t defined – so media composition varies slightly from batch to batch

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20
Q

Defined Media

A

An alternative to complex media

Contains only ingredients whose chemical composition is defined
E.g. glucose, ammonium phosphate, sodium chloride, magnesium sulfate, potassium phosphate

Is more consistent from batch to batch

Only good for growing a certain kind of bacteria

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21
Q

Obligate aerobes

A

Require oxygen

Rely solely on respiration for energy

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22
Q

Facultative anaerobes

A

Can grow in the presence or absence of oxygen

Perform respiration when oxygen is present

Perform fermentation (or anaerobic respiration) when oxygen is absent

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23
Q

Anaerobes

A

Unable to use oxygen and most are harmed by it

Perform fermentation or anaerobic respiration

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24
Q

Microaerophiles

A

require oxygen concentration lower than air

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25
Q

Psychrophiles

A

microbes that grow best in cold temperatures

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26
Q

Mesophiles

A

microbes that grow best in moderate temperatures (including room temp and core body temp)

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27
Q

Thermophiles

A

microbes that grow best in hot temperatures

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28
Q

Acidophiles

A

microbes that grow best at low pH

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29
Q

Neutrophiles

A

microbes that grow best at neutral pH

most bacteria, especially human pathogens, are neutrophiles

human body is a neutral environment; bacteria have evolved to survive in a neutral pH

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30
Q

Metabolism

A

all chemical reactions within an organism

catalyzed by enzymes (-ase suffix)

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31
Q

Alkaliphiles

A

microbes that grow best at high pH

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32
Q

Catabolism

A

Release energy (break down complex molecules)

Ex. Glucose broken down → releases energy (ATP) for bacteria to use

Catabolic processes: Fermentation, respiration

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33
Q

Anabolism

A

require energy (building of complex molecules)

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34
Q

Energy is often stored in the form of ____

A

ATP

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35
Q

Lysozyme

A

Antimicrobial enzyme present in tears and saliva

Breaks the peptide bonds between NAG and NAM residues in peptidoglycan

Part of our innate immune system (kills bacteria non-specifically)

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36
Q

Beta-lactam antibiotics

A

Inhibits the enzyme (transpeptidase) that forms the peptide bridges in peptidoglycan

Includes penicillin, amoxicillin, etc.
The antibiotics we take allow the bacteria to be targeted

Peptide bridges never get formed → weak cell wall → cell susceptible; will die shortly after

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37
Q

Confocal microscopy

A

Type of fluorescence microscopy that captures multiple planes to produce a 3-dimensional image

Stack images on top of each other

Multicolored image

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38
Q

Fimbriae

A

Hairlike appendages (spiky looking) that allow for attachment

Important for biofilm formation, colonization within host

Typically many fimbriae on the cell surface (10’s -100’s)

Composed of the protein pilin that are stacked on top of each other

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39
Q

Pili

A

Involved in motility (gliding and twitching motility)

Conjugation (sex) pilus: a special type of pilus involved in DNA transfer from one cell to another

Pilus retracts, bringing the two cells in direct contact for DNA exchange

Only one pili per cell

Also composed of the protein pilin

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40
Q

Glycocalyx

A

General term for substance found external to the cell wall

Sticky and gelatinous layer

Made of polysaccharide (or sometimes polypeptide)

Two types: Capsule and Slime Layer

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41
Q

Capsule (type of glycocalyx)

A

Common to bacterial pathogens

Protects bacteria from phagocytosis

Phagocytes kill bacteria

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42
Q

Slime layer (type of glycocalyx)

A

Produced by bacteria in nature

Protects them from their environment; not hiding

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43
Q

Sterilization

A

Removing/destroying all microbial life

Not practical or necessary in everyday life

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44
Q

Disinfection

A

Destroying harmful microorganisms
Disinfectants are applied to surfaces (inanimate objects)
Not safe on skin
Practical in everyday life
Ex. Formaldehyde, Bleach, Phenol

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45
Q

Antisepsis

A

Destroying harmful microorganisms from living tissue
Are mild forms of disinfectants
Can be used on skin
HAI: Hydrogen peroxide, Alcohol, Iodine

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46
Q

Media

A

Also called growth media or culture media
(singular: medium)

Collection of nutrients used to grow bacteria in the lab

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47
Q

Inoculate (verb)

A

The process of transferring microbes into media
“I collected some bacteria with a sterile loop and inoculated the media.”

Placing inoculated media at an appropriate temperature for growth (often uses an incubator)
“After inoculating, the media is incubated at 37C overnight.”

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48
Q

Culture

A

The practice of growing microbes in the lab (verb)
“Today in lab, we cultured E. coli on agar plates.”

Microbes grown in the lab (noun)
“When I arrived in lab, I looked at our culture from the previous class.”

“Today in lab, I inoculated media with E. coli and incubated it to generate a culture.”

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49
Q

Osmotic pressure

A

results when a solute is at different concentrations inside and outside the cell

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50
Q

Hypertonic environment

A

higher solute concentration outside the cell

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51
Q

Hypotonic environment

A

lower solute concentration outside the cell

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52
Q

Isotonic environment

A

equal concentration inside and outside of cell

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53
Q

Halophile

A

Microbe that thrives in high salt environment

Even as high as 30% (for comparison, ocean water is ~3%)

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54
Q

Allosteric Inhibition

A

Inhibitor binds the enzyme at another location, causing a conformational change and loss of the active site

Causes protein to change shape → changes active site shape

Allosteric site: somewhere other than the active site

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55
Q

Strepto

A

When the cells divide, they multiple next to each other in the same plane

Why it’s a chain

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56
Q

Staphylo

A

Sarcinae: plane of division changes each time, so it forms a cluster

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57
Q

Active Transport

A

Substances move from low to high concentration; work against concentration gradient

Requires a transporter protein and energy (ATP)

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58
Q

Cell Wall

A

Prevents osmotic lysis (cell bursting from osmotic pressure) and protects the cell membrane from environmental stressors

~99% of bacterial cells have a cell wall, but some don’t

Made of peptidoglycan (in bacteria)

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59
Q

Enrichment culture

A

A selective medium that is used to increase the number of only certain bacteria (to enrich for them)

E.g. a bacterium that is present in small number within a soil or fecal sample

Interested in one type of species in soil sample → use selective media to grow just that species

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60
Q

Turbidity

A

The cloudiness of a bacterial culture

Is proportional to the number of cells in the culture

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61
Q

Measuring Turbidity

A

Use a spectrophotometer to quantify turbidity

A beam of light is passed through the bacterial suspension to a light-sensitive detector

Light does or doesn’t get blocked by culture

Live and dead cells block light

Absorbance (or optical density, how much light gets blocked by cells in sample) is measured

Not # of cells and not if they’re dead or alive

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62
Q

Ionizing radiation

A

X-rays, gamma rays, electron beams

High energy

Ionizes water to form reactive oxygen species (ROS) that wreak havoc

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63
Q

Nonionizing radiation (UV)

A

Doesn’t penetrate surfaces

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64
Q

Sporulation

A

endospore formation; process of forming an endospore

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65
Q

Electron Microscopy

A

Uses electrons instead of photons (light)
The shorter wavelength of electrons gives greater resolution
Used for images too small to be seen with light microscopes, such as viruses
B/W image; impart color after
2 types: TEM + SEM

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66
Q

Germination

A

Re-activation of endospore to vegetative state

Senses better conditions → reactivates

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67
Q

Transmission (TEM)

A

Electrons pass through ultrathin sections of a specimen

Internal structures can be seen; image of inside of cell

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68
Q

Scanning (SEM)

A

Electrons scans the surface of an entire specimen

External structures (ex. cilia) and topography can be seen

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69
Q

Bacteria often use _____________ as their primary energy source

A

carbohydrates (sugars)

Proteins and lipids are also commonly used as energy sources, but sugars are preferred

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70
Q

Selective media

A

Designed to suppress the growth of certain bacteria (and encourage the growth of others)

Salts and dyes are often included to inhibit the growth of certain bacteria
E.g. Bismuth sulfite agar is used to select for Salmonella typhi because bismuth sulfite inhibits the growth of most other bacteria

Something is included in the media so that only certain bacteria can grow and others can’t

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71
Q

Radiation causes _________

A

Mutations (changes in DNA sequence)

After many mutations have accumulated, some (by chance) will have been lethal

Cell not able to reproduce

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72
Q

Lag Phase

A

Bacterial cells first placed in a new environment; first must ‘prepare’ for growth before reaching a max growth rate

First phase

Before log phase

No increase in population

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73
Q

Log phase (or exponential growth phase)

A

Period of unconstrained growth

Growth during this phase is exponential

When plotted on a log scale it appears as a straight line with the greatest slope

After lag phase

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74
Q

Stationary Phase

A

Follows log phase

The number of new cells being generated will soon match the number of cells dying → plateau/equilibrium

75
Q

Death Phase

A

After awhile, cell death will outweigh cell division

Follows stationary phase; downward slope

Microbial death is exponential [like growth]

76
Q

Direct microscopic count

A

Put sample on hemocytometer

Channels for sample to be injected onto, cover slip put on top

Look at cells under microscope with grid to count cells in each grid area

Apply equation to find total # of cells

77
Q

Bacteria reproduce through ______________

A

binary fission

The bacterial cell gets larger, its genome is replicated, and it splits into two

Not mitosis, not meiosis (those are eukaryotic processes)

78
Q

Generation time

A

The amount of time it takes for a bacterial cell to reproduce/to double

Some take <20 minutes (in the lab), others take >24 hours

79
Q

Peptidoglycan

A

Chain of alternating sugar residues:
N-acetylglucosamine (NAG)
N-acetylmuramic acid (NAM)

Chains are linked by polypeptide ‘bridges’: Green/blue balls: peptides (linked amino acids)

Structure wraps around the entire cell like a net

80
Q

Ribosomes

A

Complex that synthesizes/make proteins (translation)

All cells have ribosomes; bacteria have 70S ribosome

Made of protein and ribosomal RNA (rRNA)

81
Q

70S Ribosome

A

50S + 30S subunits
50+30=80, not 70

S = different unit that isn’t an additive property
Measure of how quickly molecules get centrifuged

Human Ribosome: 40S + 60S, 80S complex

82
Q

Photoautotroph

A

get their carbon from CO2 and energy from light

83
Q

Chemoautotroph

A

get their carbon from CO2 and energy from chemicals

84
Q

Chemoheterotroph

A

get their carbon from organic compounds and energy from chemicals

85
Q

Photoheterotroph

A

get their carbon from organic compounds and energy from light

86
Q

Flagella

A

Primary mechanism of motility in bacteria

Allows movement toward nutrients or away from danger; sense environment (taxis)

Composed of protein (several including the monomer flagellin)

The flagella rotates, driven by a molecular motor, propelling the bacterial cell through the environment

Flagella proteins are H antigens and distinguish among strains (e.g., Escherichia coli O157:H7)
H: refers to type of flagella (ex. Type 7)

Different bacteria have different arrangements of flagella

Not all bacteria have flagella

87
Q

Lipopolysaccharide (LPS)

A

3 parts:
Lipid A – anchors LPS into the outer membrane

Core polysaccharide – bottom part of tail, connects lipid A to O polysaccharide

O polysaccharide – chain of sugars that protrude from the cell, targeted by the host immune system (O antigen), outer part of tail

Some bacteria have a shorter version of LPS – called lipooligosaccharide (LOS)

88
Q

Porins

A

proteins embedded within the outer membrane that form channels and control entry/exit of molecules

89
Q

Passive Transport

A

Substances move from high concentration to low concentration; both simple/facilitated follow the concentration gradient, happens automatically so long as the molecule is small and uncharged
No energy expended [for simple or facilitated]
2 types: Simple + Facilitated

90
Q

Simple diffusion

A

Type of passive transport

Small, uncharged molecules can pass directly through

91
Q

Facilitated diffusion

A

Ions and large/charged molecules pass through a transporter [protein]

Driven by the concentration gradient

92
Q

Nucleoid

A

where the DNA is found

somewhere in the cytoplasm

93
Q

Bacterial chromosomes

A

circular thread of DNA that contains the cell’s genetic information

94
Q

Plasmids

A

Extrachromosomal (not apart of chromosome) genetic elements

Carry non-essential genes; Essential genes are on chromosome

Give bacteria extra abilities (ex. antibiotic resistance, production of toxins) –> Specialty genes

Look like rings

95
Q

How does temperature impact the rate of catalysis?

A

Faster reaction at high temperatures

Increase the likelihood of interaction between the substrates/enzyme; substrate is hitting active site more often

Slower reaction(s) at low temperatures

96
Q

Microbial growth

A

the growth of bacterial population (number of cells)

not the size of cells

97
Q

Microbes’ physical and chemical growth requirements

A

Physical (TOP): temperature, osmotic pressure, pH

Chemical: Nutritional requirements (carbon, oxygen, etc)

98
Q

If bacteria have _______ _________, they will continue to divide at a maximum growth rate

A

abundant resources

Eventually, resources will become depleted and the growth rate will slow

99
Q

Most probable number (MPN)

A

Used to determine if a water sample is safe to drink

Determines how much bacteria is in sample

Doesn’t tell you how much total bacteria is present, only coliform (type of bacteria)

100
Q

Low temperature has a _________ effect

A

bacteriostatic (prevents the growth of bacteria)

101
Q

Refrigeration

A

Slows growth of most microbes (not psychrophiles that grow fast at low temps)

Most human pathogens do not grow well at low temperatures; why we store food in fridge

Listeria is an exception; can still grow at low temperatures

102
Q

Freezing

A

Stops growth completely [while frozen] until thawed

An effective method of storing microbes long-term

Microbes are still there, but don’t grow while in freezer

Start growing when taken out of freezer

Helpful in laboratory setting to work with bacteria in the future/again

103
Q

How is disinfection and antisepsis often achieved using chemicals?

A

Alters membrane permeability
Damage proteins (enzymes)
Damage nucleic acids (DNA)

104
Q

Blood agar

A

A differential medium that contains blood cells that can be lysed by certain bacteria – leading to zones of clearing (hemolysis)

Tests if the bacteria being tested lyses the red blood cells

105
Q

Autoclave

A

Steam under pressure
121°C at 15 psi for 15 min
Kills all organisms/microbes and endospores

106
Q

Pasteurization

A

Reduces number of microbes
High-temperature short-time (HTST): 72°C for 15 sec
Thermotolerant organisms survive
Used in beverages (milk, juice)

107
Q

Heat as a sterilizer

A

Autoclave
Pasteurization
Moist heat
Flaming (dry heat sterilization)

108
Q

Moist heat

A

Coagulates/denatures proteins
Boiling

109
Q

Mannitol Salt Agar (MSA)

A

Both selective and differential media

110
Q

How is MSA selective?

A

It contains a high concentration of NaCl (salt), which inhibits the growth of most bacteria (except Staphylococcus spp; Staphylococcus species)

111
Q

How is MSA differential?

A

Contains mannitol (a sugar alcohol) that some Staphylococcus spp ferment while other don’t

The products of mannitol fermentation are acids, which drop the pH of the media

MSA plate contains a pH indicator → low pH turns the pH indicator (included in the media) from red to yellow

Yellow = bacteria can ferment mannitol

112
Q

Enzymes

A

Position substrates in a way that favors their conversion into products

Are almost always proteins

Can be recycled

Have specificity for certain substrates

Binding occurs in the active site (opening)
Active site is formed based on protein folding (interaction between amino acids that make up the protein)
Chemical reaction only occurs if substrate fits into active sit

Improper protein folding → wrong active site formed → chemical reaction can’t occur

113
Q

Filtration

A

Passage of substance through a screen like material

Vacuum line speeds up the process; pulls liquid through faster

Used for heat-sensitive materials (Ex. Sterilize antibiotics; antibiotics can’t contain bacteria and can’t be heated)

Membrane filters remove microbes > 0.22 μm
Smaller pore sizes are needed to filter out viruses and small bacteria
This is how viruses were first discovered; they would pass through filter

High-efficiency particulate air (HEPA) filters:
Pore size down to 0.01 μm
Can filter viruses if small enough

114
Q

Since:
The cell wall is essential for bacterial viability
And it is composed of peptidoglycan, which is unique to bacteria

Then…

A

it is an easy target for killing bacteria [without harming our own cells]

115
Q

competitive inhibition

A

Inhibitor binds to the active site, preventing the substrate from binding

Cell can make an inhibitor; prevents cell from carrying out reaction

116
Q

Gram positive cells

A

Stain purple because the primary stain (crystal violet) forms a crystalized complex (when iodine is added) within their thick peptidoglycan cell wall

Complex isn’t washed out by the decolorizer (alcohol)

Stain is stuck in the thick cell wall

117
Q

Gram negative cells

A

Thin peptidoglycan cell wall → does not retain the crystalized complex and loses its purple color when washed with decolorizer

Counterstain imparts a pink color to the Gram negative cells.

118
Q

Describe the cell wall in gram positive cells

A

Thick, multiple layers of peptidoglycan

Exposed to the environment, located outside the cell membrane

Peptidoglycan layers held together by teichoic acid and anchored to cell membrane by lipoteichoic acid

Only gram positive bacteria have teichoic acid because gram negative don’t need it; thin layer so not much to keep together

119
Q

Describe the cell wall in gram negative cells

A

Thin, single layer of peptidoglycan

Contained within the periplasm

Lipopolysaccharides (LPS) found on outer membrane’s outer leaflet

Stack: (sandwiches peptidoglycan)
Outer Membrane
Peptidoglycan (thin)
Plasma Membrane

120
Q

periplasm

A

the space between the plasma membrane and outer membrane [in gram negative cells]

121
Q

Why do only gram negative bacteria have LPS?

A

gram positive bacteria don’t have an outer membrane

122
Q

What do all bacterial cells have?

A

70CNP:
70S Ribosome
Cytoplasm
Nucleoid containing DNA
Plasma membrane

123
Q

Eukaryotic cells

A

DNA contained with a nucleus (defining difference)

Larger in size; why Hooke could see plant/animal cells but not bacterial cells

Multiple linear chromosomes, in pairs (diploid) or more copies (polyploid)

DNA wrapped around histones

Divides by mitosis

Organelles (e.g. ER, Golgi, mitochondria, chloroplasts)

Polysaccharide cell walls, when present;
Plants have cell walls made of polysaccharides
Animal cells don’t have cell walls

124
Q

Prokaryotic cells

A

Lack nucleus (defining difference)

Smaller in size

Single circular chromosome (haploid)

No histones

Divides by binary fission

No organelles

Bacteria: peptidoglycan cell walls
Archaea: pseudomurein cell walls

125
Q

Peripheral proteins

A

Sit on cytoplasmic membranes surface

Project either on the inside or outside

126
Q

Integral and transmembrane proteins

A

Penetrate the membrane, span the membrane

Wedged into the membrane

127
Q

Cytoplasmic Membrane

A

Also called ‘cell membrane’ or ‘plasma membrane’

Separates outside of cell and inside of cell

Semi-permeable membrane that encloses the cytoplasm; Allows the passage of some molecules, but not others

Made primarily of phospholipids; 2 leaflets

Also contains proteins: Peripheral + Integral and transmembrane

128
Q

Differential media

A

Designed to distinguish between bacteria based on the observable characteristics when grown on media

pH indicator included to indicate if a provided substrate is metabolized to acids/bases; pH indicator changes color based on pH changes

Something is included in the media so that anything that grows looks different

129
Q

A colony forms when…

A

a single bacterial cell is deposited onto an agar plate and divides repeatedly until visible by the naked eye

130
Q

Colonies are obtained using the…

A

Streak plate method

Starts as mixed culture → streak plate → get isolated colonies of each type (pure cultures of each type of bacteria)

131
Q

Effectiveness of treatment for killing microbes depends on:

A

Number of microbes
Environment (organic matter, temperature, biofilms)
Time of exposure
Microbial characteristics; Alcohol doesn’t kill some microbes
Disinfect for a longer period of time = more killing of microbes

132
Q

If bacteria needs energy eventually but wants to be efficient in breaking down sugar→

A

respiration

133
Q

If bacteria needs energy ASAP →

A

fermentation

134
Q

Reactive oxygen species (ROS)

A

Group of compounds derived from O2 that damage cells’ macromolecules (protein, DNA)

Ex. hydrogen peroxide (H2O2) – can be broken down by the enzyme catalase
So that H2O2 doesn’t cause damage to the cell
Bacteria in presence of oxygen can tolerate it b/c of catalase

135
Q

Purpose of liquid (broth) for growing microbes

A

When shaken in broth, all cells in the culture experience the same environment conditions (homogeneous)

136
Q

We need to provide appropriate _______ to grow bacteria in the lab

A

nutrients

136
Q

Purpose of solid (agar) for growing microbes

A

On the surface of an agar plate, bacterial cells can be separated from one another so that isolated colonies can develop after incubation

Agar is a non-nutritious solidifying agent; doesn’t serve as food to the microbes

137
Q

Carbohydrates/sugars can be broken down by bacteria through 2 routes:

A

cellular respiration + fermentation

138
Q

Cellular respiration

A

Requires O2 as final electron acceptor (only performed by aerobic bacteria)

Allows the cell to get as much energy as possible from the sugar it’s breaking down

139
Q

Fermentation

A

No O2 requirement
No Krebs cycle or electron transport chain

140
Q

Both respiration and fermentation start with __________

A

glycolysis

141
Q

Explain the process/steps of respiration

A
  1. Glycolysis
  2. Krebs cycle (aka citric acid cycle)
  3. Electron transport chain (oxygen as final acceptor; aerobic)
142
Q

An isolated colony represents a _____ __________

A

pure culture

143
Q

pure culture

A

the entire population of cells arose from a single cell

144
Q

Acid-Fast Cell Walls

A

Similar to gram-positive cell walls

Complex cell walls containing mycolic acid that imparts waxy character

Only a few bacteria: Mycobacterium spp., Nocardia spp.

Don’t stain well with Gram stain; inconsistent

Stain with carbolfuchsin (pink, with heat)

Some bacteria have no cell wall (Mycoplasma spp)

145
Q

Endosymbiotic theory

A

Larger microbial cell engulfed smaller bacterial cell, developing into the first eukaryotes

Instead of eating and destroying the bacterial cell, it keep it around and when the larger cell divided, each of the two cells received the bacteria as well → bacterial cell was a source of energy to the larger cell

Ingested photosynthetic bacteria became chloroplasts; harvest energy from light

Type of cell engulfed took light and turned it into energy
Ingested aerobic bacteria became mitochondria

146
Q

Today, if we take human cells and separate the mitochondria, the mitochondrial DNA looks like…

A

Bacterial DNA → strong evidence that what we call mitochondria today was its own independent bacteria 3 billion years ago

Chloroplast DNA looks like bacterial DNA, not plant DNA

Strengthens endosymbiotic theory

147
Q

First eukaryotes evolved how many years ago?

A

2.5 billion

148
Q

Life arose as simple organisms how many years ago?

A

3.5 to 4 billion

149
Q

Explain how too much heat damages enzymes

A

Too much heat can damage enzymes → denature

A protein is a chain of amino acids held together by strong covalent bonds (peptide bonds)

A protein folds into a distinct conformation (3D structure) due to hydrogen bonds between non-adjacent amino acids

Heat can break the weak hydrogen bonds, causing the protein to misfold

A misfolded protein is no longer functional

150
Q

After each generation, the cell population doubles in number.

Population size can be calculated using:

A

Ng = N0 * 2^g

g = the number of generations
Ng = the number of cells after g generations
N0 = the number of cells initially

151
Q

Quantitative Plate Count

A

Determines # of live cells in a given sample; population density

152
Q

2 indicators of a positive fermentation test:

A

color change (red to yellow), bubble in Durham tube

153
Q

pH

A

A measure of H+ (hydrogen ion concentration) (and consequently OH-) in a solution

On a log scale
A solution with pH 6 has 10x the [H+] than pH 7
Each unit is a 10 fold difference in H+ concentration

Most proteins fold at neutral pH

Too low or too high pH → enzymatic activity drops

Affects the folding of proteins and efficiency of enzymes
Protein = amino acids linked together
Each amino acid has charges
pH affects the charge of amino acids in proteins, which affects protein folding

154
Q

How to carry out MPN

A

Grab 15 separate tubes with broth
Into 5, transfer (ex.10mL) water in
In the next 5, transfer a smaller amount of water (ex. 1mL)
In the next 5, transfer even smaller amount (ex. 0.1mL)

Testing: the larger amount of sample being tested/added, the more likely bacteria is in sample

If so, tube contains some kind of nutrients for bacteria to grow
Yellow = bacterial growth

Example of rows: 5-3-1
Take those 3 numbers, look at table; shows MPN of bacterial per ___ mL is ___ bacteria

155
Q

Which of the following can be used as antiseptics?

A

hydrogen peroxide, alcohol, iodine

156
Q

What of the following is achieved using an autoclave?

A

Sterilization

157
Q

Central Dogma

A

The flow of genetic information

Information is stored within DNA, converted into RNA, then used to produce proteins

158
Q

In the central dogma, information is stored within ______

A

DNA

159
Q

Genetics

A

The study of heredity – how traits are passed on

Was a field before DNA was discovered

Today, genetics refers to the study of genes and DNA, including:
how DNA stores information
how the information stored within DNA is ACCESSED
how DNA is replicated

160
Q

Genes

A

segments of DNA that encode functional products, usually proteins

161
Q

Genome

A

All the genetic information in a cell

Includes all chromosomes and any other forms of DNA (e.g. plasmids)

162
Q

Chromosomes

A

Large pieces of DNA that store essential genetic information

Humans: 23 pairs of linear chromosomes

Bacteria: typically 1 circular chromosomes (many exceptions though)

163
Q

DNA Structure

A

Double helix

Backbone consists of deoxyribose-phosphate

Two strands are held together by hydrogen bonds between complementary bases:
A-T (2 H bonds)
C-G (3 H bonds)

Strands are antiparallel; 5’ and 3’ ends

Order of the bases forms the genetic instructions of the organism

164
Q

Semiconservative replication

A

Each new double-stranded DNA molecule contains one original (conserved) strand and one new strand

165
Q

Because the bases along the two strands of double-helical DNA are complementary…

A

one strand can act as a template for the production of a new strand

166
Q

Helicase

A

Enzyme that separates the DNA strands – unzips DNA

Breaks the hydrogen bonds between base pairs (denatures the DNA)

Reveals the bases so the strand can be used a template for the synthesize of a new strand

Forms a replication fork

167
Q

DNA replication involves the coordination of many ____________

A

enzymes

168
Q

As the helicase ‘unzips’ the DNA, __________ proteins bind the single-stranded DNA

A

stabilizing

Prevents degradation of the ’unzipped DNA’

169
Q

Replication fork

A

One fork moves in a clockwise direction, another fork moves counter-clockwise

Where DNA replication is occurring

Formed by helicase

170
Q

RNA primase

A

Enzyme that synthesizes a short RNA primer that is complementary to the sequence of the template strand

The RNA primer is single-stranded (and will eventually get replaced)

The RNA primer is needed because DNA polymerase can’t initiate DNA synthesis on its own

171
Q

DNA polymerase

A

Adds nucleotides to the growing DNA strand

Uses RNA primer as reference point

Reads template in the 3’ → 5’ direction

Synthesizes DNA in the 5’ → 3’ direction

Moves away from helicase

172
Q

After the DNA polymerase begins synthesizing DNA, the RNA primer is removed by ______

A

RNase

173
Q

DNA Ligase

A

glues together Okazaki fragments in the DNA

174
Q

Why does the lagging/leading strand situation exist?

A

DNA polymerase can only read in 3’ to 5’ and synthesize in ‘ to 3’

175
Q

The field of genetics includes (select all that apply)

A

the study of heredity
how DNA stores information
how the information stored within DNA is accessed
how DNA is replicated

176
Q

DNA replication is semi-conservative meaning that …

A

Each double-stranded DNA molecule contains one original strand and one new strand

177
Q

Which of the following enzymes are involved in DNA replication?

A

Helicase, RNA primase, DNA polymerase

178
Q

Which of the following accurately describes the movement of DNA polymerase during replication of bacterial DNA?

A

DNA polymerase only reads the template strand in the 3’ to 5’ direction

179
Q

Which of the following statements about the lagging strand are correct?

A

DNA synthesis on the lagging strand results in the production of Okazaki fragments

DNA polymerase on the lagging strand moves away from the helicase

180
Q

Disk-Diffusion Method

A

Evaluates efficacy of chemical agents

Filter paper disks are soaked in a chemical and placed on a culture lawn

Measure the zone of inhibition (ZOI) around the disks
Larger ZOI → more effective

Testing ability of chemical to kill the bacteria on the plate

181
Q

Why does DNA replicate?

A

It wants to divide so the DNA has to be copied so that each cell has a copy of the DNA

181
Q

Leading Strand

A

Synthesized continuously

DNA polymerase moves toward the helicase

182
Q

Lagging Strand

A

DNA is synthesized in short patches (Okazaki fragments)

DNA polymerase moves away from helicase