Test 2 Flashcards
(146 cards)
1
Q
Two locations microbes can grow
A
In suspension or attached to surfaces
2
Q
What is it called when microbes are grown in suspension
A
Planktonic growth
3
Q
What is it called when microbes grow attached to a surface
A
Biofilm
4
Q
Is it more common to grow free or attached
A
Attached (80%)
5
Q
What surfaces can microbes grow on
A
Nearly any natural or artificial surface exposed to microorganisms can be colonized
6
Q
What can microbes grow on in hospitals
A
Catheters and intravenous lines
7
Q
Why is being attached to a surface beneficial
A
- Greater access to nutrients and protection (stay in favorable habitat without getting washed away)
- Resist phagocytosis by protozoa and immune system
- Living close together facilitates cell to cell communication, nutrient and genetic exchange
- Penetration of antimicrobial agents may be slow or prevented
8
Q
What is the default mode of growth
A
Biofilm
9
Q
What adaptation must microbes have to be planktonic
A
Must be adapted to low nutrient concentrations
10
Q
Are biofilms one species?
A
No, many species
11
Q
What keeps biofilms together
A
Adhesive matrix produced by the cells
12
Q
What is the matrix made of
A
Polysaccharides, proteins, and nucleic acids (DNA)
13
Q
How do things get through the matrix
A
It is pourous, has channels to take in nutrients and expel waste
14
Q
What happens to the biofilm as it grows
A
The inner region becomes anoxic which creates a niche for anaerobic and faculative aerobes
15
Q
Are planktonic or biofilms more resistant to antibiotics
A
Biofilms, 1000 times more
16
Q
What do biofilms cause in humans
A
Deadly infections
17
Q
Why is antibiotic resistance increased in biofilms
A
- Slower growth rate in biofilms. Cells may be nutrient or oxygen deprived. Antibiotics are most effective on metabolizing/growing/dividing bacteria
- Contain persistor cells that become dormant in the presence of antibiotics
- Reduced penetration of antimicrobial agent due to electrical charge of ECM
- Expression of genes that increase tolerance to stress (efflux pumps)
18
Q
Persister cells
A
Rare cells (few in #) that are transiently tolerant to multiple antibiotics Viable by dormant
19
Q
What forms persister cells
A
A population of antibiotic sensitive bacteria
20
Q
How do persister cells compare to their antibiotic susceptible sisters
A
Genetically identical
21
Q
Is persistance genetic or passed on by horizontal gene transfer
A
NO
22
Q
Why aren’t persister cells killed by antibiotics
A
Antibiotics kill cells with active processes. They are dormant
23
Q
What is the cause of recurring infections
A
Persistance
24
Q
What causes chronic TB
A
Mycobacterium tuberculousis
25
What causes CF
Pseudomonas aeruginosa
26
Components involved in persister cell formation
1. Toxin-antitoxin modules
2. The stringent response
3. Phenotypic heterogeneity
27
Toxin antitoxin modules (TA modules)
Region in the genome that codes for a toxin that inhibits cell growth and an antitoxin that counteracts the activity of the toxin. Found in almost all bacteria and archaea
28
What encodes for the TA module in e coli
Hip AB
29
What is the toxin in e coli
Hip A (inhibits translation)
30
What is the antitoxin in e coli
Hip B (sequesters Hip A)
31
What degrades Hip B
Lon (protease)
32
Normal state of TA module
Hip B and Hip A complex resulting in neutralizing of Hip A
33
Path to persistence
1. Lon is activated by PolyP (polyphosphate)
2. Lon degrades Hip B
3. Hip A is now free to inhibit translation
4. Shut down of protein synthesis stops cell growth
34
Why do bacteria use the stringent response `
To survive nutrient deprevation, environmental stress, and antibiotic exposure
(recalibrates metabolic rate in response to environment)
35
Process of stringent response
Shutdown of macromolecule synthesis (leads to decrease in rRNA and tRNA, no new ribosomes and protein synthesis reduced). DNY synthesis decreased
36
What is activated by stringent response
Biosynthesis of new amino acids to synthesize amino acids no longer found in the environment. Made by existing ribosomes. rRNA synthesis and ribsome production continues but at reduced rate
37
Phenotypic heterogentiy
While cells of a clonal population are gentically identical but there are differences in gene expression and protein content
38
What causes differences in gene expression and protein content
Unequal distribution of macromolecules during cell division
39
What do some cells randomly produce more of
Poly P (explains why some cells convert to persister and others dont)
40
Where are efflux pumps located
Embedded in the cell membrane
41
Function of efflux pumps
Transport molecules including antibiotics out of cells
42
Why do efflux pumps do this
Allows the cell to surivive at higher external concentrations of the antibiotic
43
How do efflux pumps contribute to multidrug resistance
Transport different classes of antibiotics outside the cell
44
Efflux pump of e coli
AcrAB-TolC
45
What does the e coli efflux pump pump out
Rifampicin, chloramphenicol and fluroquinolones
46
What besides the polsaccharide matrix of biofilms decreases antibiotic permeability
Efflux pumps changing gene expression
47
Where do you find biofilms
1. Pipes and drains
2. Hulls of ships (decreases speed and efficiency)
3. Within oil and fuel tanks (spoilage)
4. Medical implants (heart valves, joints, catheters)
5. Middle ear (ear infection), lungs (CF)
6. Human mouth (dental plaque)
7. Human GI (helpful)
48
Components of dental plaque
Salivary proteins, food debris, and mass of bacterial cells
49
What does plaque harden into if not taken care of
Tartar
50
Stages of biofilm formation
1. Attachment
2. Colonization,
3. Development
4. Dispersal
51
What accounts for the inital attachment
Random collision
52
What facilitates attachment
Flagella and pili (or cell surface proteins)
53
What does attachment signal
Expression of biofilm-specific genes encoding proteins that produce intracellular signaling molecules and extracellular polysaccharides
54
What does the cell lose when it commits to being a biofilm
Flagella (no motility)
55
How can cells be released from the biofilm
Active dispersal
56
What happens duiring colonization
Intracellular communication, growth, and polysaccharide formation
57
What happens during biofilm development
More growth and polysaccharide
58
What triggers active dispersal
Environmental factors such as nutrient availability
59
Biofilm maturation I
First colonists facilitate arrival of other cells by providing more diverse adhesion sites and builidng polysaccharide matrix to hold biofilm together. Cells divide as nutrients accumulate
60
Biofilm maturation II
Biofilm is fully mature and will only change in shape and size. Matrix acts as protective coating
61
What molecule sends signals to guide bacteria into biofilm formation
Accumulation of regulatory molecule c-di-GMP
62
Where is c-di-GMP widely distributed
Only in bacteria
63
What does synthesis and degradation of c-di-GMP depend on
Environmental and cellular cues
64
Physiological events triggered by c-di-GMP synthesis
Binds proteins that reduce activity of flagellar motor, reduces attachment proteins, and mediated biosynthesis of extracellular matrix polysaccharides
65
What type of messanger is c-di-GMP
Second
66
Where do messages from c-di-GMP get transmitted from
Receptors on cell external membrane
67
Where do the transmitted messages go
To targets within the cell
68
What is altered within the cell by these messages
Metabolism and motility
69
How can some cells have more c-di-GMP
Divided unevenly during cell division (pseudomonas)
70
Cells with more c-di-GMP characteristics
Remain still, adhere to surfaces, and form colonies
71
Cells with less c-di-GMP characteristics
Actively swim about by using their flagellum
72
Bacteria that commonly form biofilms
Pseudomonas aeruginosa and Vibrio chloera
73
What type of bacteria is pseudomonas
Opportunistic pathogen
74
Where is pseudomonas found
Soil
75
What does pseudomonas infect
Blood, lungs, urinary tract, ears, skin and other tissues
76
What causes CF
Thick biofilm in lungs
77
How do cells communicate in a biofilm
Quorum sensing
78
What signals cells that their population is growing
Accumulation of acyl homoserine lactones (AHLs)
79
What does growth in numbers trigger
Extracellular polysaccharide and c-di-GMP synthesis
80
What types of signalling does vibrio cholerae use
Inter and intra
81
What does quorum sensing do in vibrio cholera
Acts opposite as in P. aerunigosa
| Accumulation of quorum signaling molecules represses biofilm formation genes and activates flagellar and virulence genes
82
What triggers biofilm formation in vibrio cholerae and why
Low densities repressed by high cell densities
1. More likely to occur when nutrients are more plentiful (Natural environment)
2. Allows cell attachment to marine surfaces for better acces to nutrients and protection
83
Ways to battle biofilms
1. Surgery- remove and replace implants
2. Block quorum sensing (drugs)
3. Drugs to interrupt or alter c-di-GMP
4. Coating medical devices with substances that inhibit microbial growth (silver)
5. Exposure to electrical fields (disrupts clinging ability)
6. Copper based metal (chitin)
7. High frequency altering magnetic fields
8. Antibodies that targer eDNA and DNA binding proteins
84
Microbial mats
Extremely thick biofilms that exist as multilayered sheets with different organisms present in the layers. Composed of phototropic and chemotropic bacteria
85
What causes layers in microbial mats
Availability of resources
86
Where are microbial mats common
Hot springs and intertidal regions (high temp, high salt --> reistrict grazing from small animals)
87
How long have microbial mats existed
3.5 billion years
88
Most studies microbial mats
Cyanobacterial
89
Type of bacteria of cyanobacterial mats
Oxygenic phototrops that use light to synthesize orgtanic material from CO2
90
Signal transduction
Used to regulate cell metabolism in response to changes in temperature, pH, oxygen, nutrient availability or changes in number of cells present
91
What does signal trasduction occur in response to
Phosphate or nitrogen limitation and changes in osmotic pressure
92
Two part regulatory system
1. Sensor kinase protein
| 2. Response regulator protein
93
What is the job of a kinase
Enzyme that puts on a phosphate
94
What is the job of a phosphatase
Takes off phosphate
95
Where does the kinase get the phosphate from
ATP
96
Where are sensor kinases
Cell membrane
97
What is the job of sensor kinases
Detect a signal from the environment and phosphorylate themselves (autophosphorylation at the histidine residue histidine kinases)
98
Where do sensor kinases transfer the phosphate to
Response regulator protein
99
What is the response regulator protein
DNA binding protein
100
Where is the response regulator protein located
Cytoplasm
101
What does the response regulator protein do when it is bound to DNA
Affects gene transcription:
positive activates transcription
nagative represses transcription
102
What determines the response to the regulator protein brinding
A feedback loop (phosphotase removes the phosphate from the regulator protein)
103
How many two component systems in ecoli
50
104
Key players in reponse to osmolarity system in e coli
Omp C, Omp F, EnvZ, Omp R-P
105
Omp C and Omp F
Gm- oter membrane porin proteins
106
EnvZ
Sensor kinase
| Detects changes in osmotic pressure and autophosphotates
107
Omp R-P
Response regulator
| Receieves phosphate from EnvZ
108
Omp C
Smaller pore, synthesis is upregulates when osmotic pressure is high
109
Omp F
Longer pore, synthesis is upregulated when osmotic pressure is low
110
Low osmotic pressure result
OmpR activates transcription of OmpF gene
111
High osmotic pressure result
OmpR represses transcription of OmpF and activates transcription on OmpC
112
Quorum sensing
Regulatory mechanism in which bacteria sense and respond to the presence of their own kind
113
Essentilally, bacteria are sensitive to _____ of their own kind
Cell density
114
Quorum sensing occurs widepread in gram ______ bacteria
Negative
| Sometimes in gram positive
115
What other species is quorum sensing seen in
Some archaeal
116
Purpose of quorum sensing
Used to ensure sufficient cell numbers are present before initiating activities that require a certain cell density to work efficiently
117
Example of quorum sensing
Toxin production
A single bacterium toxin will have no effect and is a waste of resources. Many cells toegther can produce toxin to cause disease
118
Autoinducer
Synthesized by species that used quorum sensing
119
How does the autoinducer travel
Freely diffuses through the cell membrane in either direction
120
How do high concentrations of the autoinducer accumulate
Only if many cells are nearby making the same autoinducer
121
First identifies autoinducer
Acyl homoserine lactones (AHLs)
122
Gram positive bacteria autoinducer
Autoinducer 2 (AI-2)
123
What are autoinducers made of
Short peptides
124
What does the autoinducer bind to
Transcriptional activator protein or sensor kinase of a two component system
125
What does the autoinducer trigger
Transcription of specific genes (affects gene expression)
126
What was QS first identified in
Bioluminescent bacteria
127
What enzyme generates light
Luciferase
128
Where are genes encoding luciferase grouped
Lux operon
129
Regulatory genes that control the lux operon
Lux R and Lux I
130
Lux R
Responsible for the synthesis of activator protein
131
Lux I
Synthsis of enzyme needed for AHL production/autoinducer
132
AHl in e coli
AI-3
133
What does AI-3 do
Induce virulence
134
What happens as e coli populations rise in the intestines
AI-3 levels rise
135
What hormones do the intestinal cells produce when e coli is present
epinephrine and norepinephrine
136
What do the signal molecules bind to in the e coli cytoplasmic membrane
Sensor kinases
137
What does binding to the sensor kinases in e coli cause
Phosphorylation and activation of two transcriptional activator proteins with result in toxin production and proteins that form lesions in intestinal mucosa
138
Ideal target for manipulating bacteria and suppressing virulence and biofilm formation
Silencing communication
139
How many pieces of DNA do bacteria have
One
140
How many bacterial cells in a human
10 trillion (10x more than human cells)
141
How many more bacteiral genes do we have
1000x more
142
What happened when the glowing bacteria were alone
No light
143
What happened when the glowing bacteria were put together
Glow
144
How does quorum sensing work
Cells have signal producing protein that produces signals to be released from cell. The cell also has a receptor. When the signals accumulate the receptor will receive signal to know it has neighbors and group behavior genes are activated
145
Why are molecules released different in each species
Only intraspecies communication so it can count its own kind
146
How do bacteria communicate with other species to find out what others are around them
Have second signal producing protein that produces generic signals that all bacterial cells understand. Each has receptor and molceule is the same in every species
