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Microbiology Quiz 1 > Microbio 3-19 growth metabolism > Flashcards

Microbio 3-19 growth metabolism Flashcards

1
Q

How does an infection occur?

A

disruption of physical barriers (ie surgical sites/burns), immune dysfunction, or perturbations of the immune system

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2
Q

What is the generation time?

A

time required for the population to double

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3
Q

What is the generation time for a typical bacterium?

A

It varies depending on the organism. It can be as short as 20 minutes or as long as 20 hours, but many pathogens have generation times of less than 30 minutes

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4
Q

What limits the growth of a pathogen? (5)

A

1) exhausted nutrient supplies or key resources. 2) Accumulation of toxic metabolic products. 3) Antibiotics from neighboring microbes/humans. 4) Immune system. 5) Environmental conditions

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5
Q

What are the major nutrients required for bacterial growth? 5)

A

Carbon, Nitrogen, Phosphorus, Sulfur, Iron (C-SPIN)

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6
Q

Nutrient sources serve 2 major functions. What are they?

A

1) energy source. 2) source of carbon for the synthesis of all cellular components. Ex: in the presence of O2, many bacteria can oxidize ~50% of glucose -> CO2+H2O, which produces enough energy/ATP to convert the remaining 50% of the glucose to biomass (cellular components)

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7
Q

What are 5 potential host sources of C, N, and S that pathogens use? What are 2 additional sources of N?

A

1) amino acids 2) peptides 3) proteins 4) nucleotides 5) phospholipids. Ammonia (NH4+) and nitrate from the diet or NO (produced by the immune response) are also possible nitrogen sources

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8
Q

T/F The carbon sources that bacteria use can be diagnostic.

A

True.

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9
Q

Neisseria gonorrohoeae and Neisseria meningititidis can be distinguised based on the carbon sources that they use. What are they and how are they different between the two strains?

A

Neisseria gonorrhoeae can grow in glucose but NOT maltose, whereas Neisseria meningititidis can grow in glucose & maltose.

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10
Q

What is the significance of the proteases that bacteria secrete?

A

a.a. and peptides can be taken up by bacteria, but proteins cannot because they are too big. Thus proteases serve to degrade the proteins into smaller fragments (a.a. and peptides) that the bacterium can take up and use for C, N, and P sources.

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11
Q

What is the significance of the nucleases (RNAse, DNase) that bacteria secrete?

A

to break down available RNA and DNA so that they can be used as C, N, and P sources, or for their own DNA/RNA synthesis

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12
Q

What is an inducer of nucleases (RNAse, DNase) production in pathogens?

A

P sources

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13
Q

What is the significance of the phospholipases that bacteria secrete?

A

it acts to liberate phospholipids from host cell membranes or lung surfactant, which then provides microbes with C, N, and P sources.

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14
Q

What is an inducer of phospholipase production in pathogens?

A

low phosphorus or low iron levels

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15
Q

Host cell lysis by phospholipase activity yields this:

A

Iron (Fe)

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16
Q

Iron liberated from host cell lysis is used for:

A

generation of ATP via the ETC

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17
Q

Describe how iron (Fe) sources are “shared” between the host and the pathogen.

A

The host makes Fe-binding proteins that make iron unavailable to microbial invaders. However, the microbial invaders produces siderophores (iron cheloators) that can extract iron from host reserves.

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18
Q

Define virulence determinants (virulence factors)

A

mechanisms that a pathogen employs to establish itself and produce the subsequent disease

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19
Q

What are examples of virulence determinants that pathogens use?

A

proteases, nucleases, phospholipases, siderophores

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20
Q

What are siderophores?

A

iron chelators that bacteria produce that has a very high affinity for Fe.

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21
Q

What happens if the pathogen cannot secrete siderophores?

A

Since serve to sequester Fe for the pathogen to use (in the production of ATP), the pathogen becomes avirulent if it cannot produce siderophores

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22
Q

What are extracellular and intracellular examples of siderophores that deliver Fe from the host to the pathogen?

A

Extracellular: transferrin, lactoferrin. Intracellular: Ferritin, hemoproteins, phopholipase (causes cell lysis and subsequent release of Fe). (think: E-TL; I-PFH)

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23
Q

What are growth factors (in the pathogen world)?

A

organic compounds that are used to make metabolites that the bacterium cannot synthesize themselves. NOTE: they are not metabolized to supply energy!

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24
Q

Different organisms require different growth factors. What is the difference between a fastidious bacterium and a prototrophic bacteria?

A

Fastidious: require many growth factors to grow and are usually commensal bacteria that live in the GI tract where there is a continuous supply of nutrients. Prototrophic: can synthesize everything it needs to grow.

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25
What is the evolutionary advantage of fastidious bacterium?
they don't have to synthesize anything themselves -- they can just get it from the host.
26
Haemophilus requires these two factors in order to grow.
they can only grow on medium containing heme and NAD+
27
What are 3 environmental factors that affect the growth rate (generation times) of a pathogen?
1) temperature. 2) pH. 3) osmotic conditions
28
What is the optimal temperature for most pathogens?
37C
29
What is a pathogen that can grow at a reduced body temperature?
Micobacterium leprae - optimal growth at reduced body temperatures (and poorly at 37C), which is why the lesions are present on the skin and not on internal organs
30
What is a pathogen that can grow at an elevated temperature (>37C)?
Legionella
31
What is a pathogen that can grow at an low temperature (>4C)?
listeria (a causative agent of food poisoning)
32
What is the optimal pH for most pathogens?
pH 6-8, optimum 7.4
33
How does a lower pH affect the growth rate of a bacterium?
low pH can inhibit the growth of unwanted bacterium or by reducing the heat resistance of the microbe (such that they become more sensitive to heat)
34
How can bacteria affect their local pH?
by producing acid or releasing ammonia (from metabolic products) to make the growing conditions more favorable.
35
How does the production of urease by the bacterium make their environment more favorable? What is an example of a bacteria that does this?
Urease converts urea -> NH3, which raises the local pH to make the local growing conditions more favorable. This mechanism is employed by Helicobacter (whih causes gastric ulcers and cancers) to raise the local pH in the stomach to make it more hospitable for them
36
How does the osmotic gradient affect the growth rate of a bacterium? What is an exception to this?
very high salt/sugar concentrations can inhibit the growth of many pathogens. Staph Aureus is salt resistant and can cause food poisoning associated with salty foods (ie hams) if not properly handled.
37
What is a bacterium that is generally associated with food poisoning from ingesting salty foods (ie hams)
staph aureus
38
Why is it that most bacteria do not need to regulate their own internal osmolarity with exact precision?
because they are enclosed by a cell wall that is capable of withstanding a considerable internal osmotic pressure.
39
What are the components of the common growth medium?
peptone with glucose added
40
What is peptone?
peptic digest of meat containing peptides and a.a.
41
What is the purpose of peptone and glucose in the common growth medium?
serve as carbon sources and additional sources of energy
42
T/F Blood agar supports the growth of _____% of pathogens
90%.
43
What is the purpose of using a solid medium? (3)
1) obtain pure cultures of bacteria. 2) observe colony morphology. 3) quantification
44
Why is the measurement of bacteria important in clinical settings? (2)
1) to determine if there is an infection. 2) antibiotic susceptibility testing needs to be done with cultures at a known density to be accurate.
45
Which clinical samples should you expect 0 bacteria?
CSF
46
T/F Urine is sterile and therefore does not contain any bacteria.
Generally true, but it is expected to find some organisms, so levels matter.
47
What are 4 ways that you can measure bacteria?
1) optical measurements using a spectrophotometer. 2) determination of metabolic activity (using dyes that measure ETC activity, redox activity, and ATP levels). 3) direct measure of cell # using a counting chamber. 4) viable/plate counts by measuring CFU
48
What does the CFU indicate?
number of viable bacterial cells in a sample.
49
What are the 4 phases of growth in the bacterial growth curve?
Lag, Log, Stationary, and Death
50
What is the lag phase characterized by in terms metabolic activity and cell number? What underlying biological activities is observed?
increased metabolic activity, but no increase in number of cells. Observe increase in: 1) synthesis of macromolecules (RNA, proteins) for new growth 2) cell mass and 3) size
51
What is the lag phase influenced by? (4)
1) kind of bacteria. 2) age/size of inoculum. 3) nature of the medium from which they were taken. 4) nutrients present in the new medium
52
What is the log phase characterized by?
cells numbers increase in a logarithmic manner, with a CONSTANT generation time
53
How do most bacteria reproduce?
binary fission
54
What influences the rate of cell division during the log phase? (4)
1) type of organism. 2) nature of medium. 3) temperature. 4) rate of aeration (for aerobic bacterias only..duh)
55
What is meant by "balanced growth"?
an orderly increase of ALL cellular components. Thus, a doubling of biomass is accompanied by a doubling of all other components (protein, RNA, DNA). After doubling in size, each cell divides to yield two identical cells.
56
What is the stationary phase characterized by?
slowing of logarithmic growth, until growth = death, due to the accumulation of 1) waste products, 2) nutrient depletion, 3) change in pH, 4) decrease in oxygen tension.
57
What is the death phase characterized by?
rate of death/clearance >> rate of growth, and the number of viable cells decline.
58
In terms of disease and infection, what is the lag, exponential, stationary, and death phase characterized by?
LAG: adaptation to host environment. EXPONENTIAL: rapid growth to replace losses to host defenses. STATIONARY: increased resistance to host defenses and antibiotics. DEATH: growth rate is slower than the death/clearance rate
59
In a clinical sample, which one will have a SHORTER lag phase: a latent infection or an acute infection?
the acute infection will have a SHORTER lag phase becauase it's already has syntheized or is in the process of synthesizing all of the macromolecules it needs for replication
60
When glucose is a carbon source, what is generated/consumed as it undergoes glycolysis, TCA, and ETC?
Glycolysis: generates ATP + NADH. TCA: generates NADH/FADH2. ETC: consumes NADH + generates a H+ gradient to make ATP
61
What is the difference between substrate level phosphorylation and oxidative phosphorylation?
Substrate level phosphorylation: occurs during glycolysis and Krebs cycle, where a free phosphate is physically added to ADP to form ATP. Oxidative phosphorylation: occurs on the ETC, where ATP is synthesized indirectly from the creation of a H gradient and the movement of it down its gradient via ATP Synthase
62
Why do bacteria require energy? (2)
1) motility and 2) drug efflux pumps, which contributes to the drug resistance observed in bacteria.
63
What happens to glucose during glycolysis?
it is oxidized to pyruvate
64
During glycolysis, how many NET moles of ATP is produced and how many equivalents NADH is formed for every mole of glucose that is oxidized to pyruvate?
2 ATP and one equivalent of NADH is formed from NAD+
65
What happens during the TCA cycle?
glucose intermediates (pyruvate) is oxidized to CO2 + H2O, and 6 NADH/2 FADH2 is generated per mol of glucose
66
What is the importance of the TCA cycle in ATP generation??
it generates even more 6 NADH/2 FADH2 (per mol of glucose) that will ultimately be used to drive ATP formation via oxidative phosphorylation in the ETC
67
Why do pathogens use glyoxylate shunt?
Pathogens that become phagocytosed by macrophages use the glyoxylate shunt to utilize the carbon sources within the macrophage (ie lipids and cholesterol). The ability for pathogens to use lipids via the glyoxylate cycle is critical for their survival wtihin lipid rich environments such as the macrophage
68
What is the primary carbon source of the glyoxylate cycle?
acetyl CoA - produced from the direct activation of acetate or from oxidative degradation of ethanol, lipids, or free fatty acids.
69
What is the ETC?
electrons are transferred from e- donors (NADH/FADH2) to a series of e- acceptors such as cytochromes and flavins, and ultimately O2, in redox reactions. The energy released by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane, which generates potential energy in the form of a pH gradient and an electrical potential across this membrane. The protons flow back across the membrane and down the gradient, through the ATP synthase, which uses this energy to generate ATP from ADP.
70
T/F anerobic bacteria does not undergo respiration.
False. Some bacteria can undergo anaerobic respiration by using terminal e- acceptor other than oxygen (ex: nitrate (NO3-) can be reduced to N2)
71
What is anaerobic respiration?
when a substance other than O2 is used as an e- acceptor
72
What is the difference between the TCA cycle and fermentation in terms of ATP and NAD+?
TCA: pyruvate is oxidized to CO2 + H2O, generating NADH and FADH2 in the proceess that is used in the ETC cycle to produce ATP. FERMENTATION: pyruvate is reduced to lactic acid and NAD+ is regenerated. No additional ATP is produced.
73
What is fermentation?
conversion of sugar to acids, alcohols, and/or gases (CO2)
74
What is one bacteria that uses lactic acid fermentation? Why is this important clinically?
Lactobacilli uses fermentation to produce lactic acid, which creates a low pH environment that is important for vaginal health (ie it protects against yeast infections).
75
lactobacilli uses this type of fermentation
lactic acid fermentation
76
What are the end products of lactic acid fermentation of glucose?
lactic acid, ethanol, and CO2
77
A high pH in the vagina is associated with these types of symptoms:
bacterial vaginosis, fungal infections, HIV, pelvic inflammatory disease
78
What bacteria uses butyric acid fermentation?
Clostridia uses this pathway to generate butyric acid, CO2, H2, and small amounts of alcohol from the fermentation of sugars. Butyric acid is protective against intestinal pathogens (ie E coli O157:H7, which is responsible for hemorrhagic colitis)
79
Colstridium butyricum uses this pathway of fermentation
butyric acid fermentation
80
What are the end products of butyric acid fermentation of glucose?
butyric acid, CO2, H2, and small amounts of alcohol
81
What bacteria uses propionic acid fermentation?
Propionibacterium and Bifidobacterium (both corynebacteria), which ferments lactate (end product of lactic acid fermentation) to acetic acid, CO2, and propionic acid
82
Colstridium butyricum uses this pathway of fermentation
propionic acid fermentation
83
What are the end products of propionic acid fermentation of glucose?
propionic acid, acetic acid + CO2
84
What type of bacteria and fermentation process is used to make swiss cheese?
propionic acid bacteria, propionic acid fermentation. Swiss cheese is distinguished by the distinct flavor of propionic and butyric. Holes are caused by the entrapment of CO2
85
What type of bacteria is implicated in the pathogenesis of acne? What type of fermentation does it use?
Propionibacterium acnes are found in the deeper follicles in the dermis. Uses proprionic acid fermentation to produce propionic acid, which are thought to keep other microbes from growing in these niches.
86
Enteric microbes use what type of fermentation?
mixed acid fermentation
87
What are the products of mixed acid fermentation?
Depends on the bacterium, but Shigella converts pyruvic acid to formic acid, whereas Salmonella has an enzyme that converts pyruvic the formic acid to CO2 and H2 gas. The remainder of the products formed during the mixed acid fermentation is ethanol, acetic acid, succinic acid (all derived from acetyl CoA)
88
The H2 gas produced by Salmonella in mixed acid fermentation is important because_.?
it is a unique bacterial product that is never produced by mammalian cells. Since it is an insoluble gas, it is readily detected in tissues during infections by these bacteria.
89
The H2 gas produced by Salmonella (and other bacteria such as Clostridium perfringens, Staphylococcus aureus, and Vibrio vulnificus) in mixed acid fermentation results in_?
gas gangrene
90
How is the detection of acetoin relevant for water microbiologists?
Acetoin is used to distinguish a non-fecal enteric bacteria from a fecal enteric bacteria
91
What are examples of mixed acid fermenters?
Salmonella, E. Coli, and Shigella
92
Which two bacterias use ethanol fermentation?
Saccharomyces cerevisiae (yeast) and Candida albicans (fungus)
93
What is produced in ethanol fermentation?
pyruvic acid is converted to ethanol and CO2
94
What is the Stickland Reaction?
fermentation process in which energy is generated from the fermentation of PAIRS of a.a. to produce decarboxylated derivatives of a.a., which are volatile and malodorus (and responsible for the foul odor associated with some anaerobic infections) One a.a. serves as the e- donor while the other serves as an e- acceptor.
95
Bacteria can be classified into these 5 different categories based on their relationship with oxygen.
1) Obligate aerobes. 2) Facultative anaerobes. 3) Obligate anerabes. 4) Aerotolerant anaerobes. 5) Microaerophiles "A-FOAM"
96
What are obligate aerobes?
O2 required for growth.
97
Where do obligate aerobes obtain their energy from?
Energy gained through respiration via ETC
98
What are facultative anaerobes?
can grow under aerobic and anaerobic conditions, AND also have fermentative capacity.
99
Do facultative anaerobes grow better under aerobically or anaerobically?
Exhibits better growth under respiration because more ATP can be produced that way, obviously
100
What are obligate anaerobes?
cannot grow in the presence of oxygen.
101
What are examples of obligate anaerobes?
bacteroides fragilis (in intestines and anoxic abcesses)
102
Where do obligate anaerobes obtain their energy from?
Can only obtain energy from fermentation mechanisms and do not have cytochromes or ETC.
103
What do obligate anaerobes produce upon exposure to oxygen?
H2O2
104
When is H2O2 formed by obligate anaerobes? What happens when H2O2 is formed?
ROS forms from H2O2, which damages DNA and proteins/enzymes.
105
What inactivates H2O2?
catalase
106
Which bacteria can inactivate H2O2? What enzyme do they use?
obligate aerobes
107
Which bacteria contains catalase? Which bacteria lacks catalase?
Obligate aerobes contain catalase. Obligate anaerobes lack catalse.
108
What reaction does catalase do?
converts H2O2 --> H2O and CO2
109
What two enzymes do obligate anaerobes lack? Whats the significance of this?
catalase (which breaks down H2O2 --> H2O and CO2) and superoxide dismutase (which breakdown O2- + 2H+ --> H2O2 + H2O). These can accumulate and damage the bacterium if it is exposed to oxygen.
110
What are aerotolerant anaerobes?
grow exclusively and robustly via fermentation, but these bacteria are indifferent to O2 and can thus can survive oxygen exposure.
111
Lactobacillus, Stretpococcus, and Clostridium have this type of relationship with oxygen.
aerotolerant anaerobes - grow exclusively via fermentation (but can still grow in presence of O2)
112
What are examples of aerotolerant anaerobes?
Lactobacillus, Stretpococcus, and Clostridium (tetani and botulinum)
113
What are microaerophiles?
organism that requires or tolerates oxygen only if it is at a LOWER concentration (5%) than is found in air (20%)
114
What is an example of a microaerophile.
campylobacter jejuni
115
Where do anaerobes exist within the host?
mouth, urinary tract.
116
How can anaerobes exist within the mouth, an area that is exposed to oxygen?
other bacteria (aerobic/facultative) is present, or the host tissue is using up the O2 and allowing the anaerobe to grow.
117
Anaerobes can grow in the presence of oxygen if and only if_.
reducing agents are present, which remove oxygen from the growth medium
118
How can you determine whether a pathogen can ferment a particular substrate?
use a pH indicator and a gas detection system
119
T/F Enteric E. coli can ferment glucose + lactose.
True.
120
T/F Enteric Salmonella can ferment glucose + lactose.
False. It can ferment glucose but NOT lactose because it lacks the enzyme that cleaves lactose

Microbiology Quiz 1 (6 decks)

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