Bacterial Structures Flashcards
1
Q
Al bacterial cells must possess
A
cell membrane, genome, ribosomes, intracellular macromolecules, almost always a cell wall
2
Q
Extrachromosomal elements (ECE)
A
plasmids or prophages may be present
3
Q
Describe a bacterial ribosome
A
70S (50S + 30S)
4
Q
What are 3 cell surface structures that may or may not be present on bacteria
A
Flagella, Pili, Capsules
5
Q
dipococci
A
pair of cocci
6
Q
streptococci
A
chain of cocci
7
Q
staphylococci
A
cluster of cocci
8
Q
antimicrobics may alter
A
cell morphology (shape and arrangement)
9
Q
Flagella or antigen ____
A
H
10
Q
Flagella is composed of
A
polypeptides - different than pili
11
Q
Plain flagella
A
extend from the cell surface into the environment for motility
12
Q
Endoflagella of spirochetes
A
internal structure that allow them to perform a corkscrew movement
13
Q
Flagella function to
A
provide motility in liquid and some surface translocation
14
Q
What allows flagella to propel?
A
sensory system control via chemotaxis
15
Q
Virulence factor of flagella
A
motility with chemotaxis
16
Q
H-antigen
A
flagella
17
Q
Pili are composed of
A
polypeptide chain - different than flagella
18
Q
Normal pili and sex pili
A
extend out from the cell surface into the environment
19
Q
Pili functions to
A
aid in adherence to host, antiphagocytic, involved in surface translocation (pili type IV)
20
Q
Sex pilus function
A
conjugation (spread of antibiotic resistance)
21
Q
Another name for capsules
A
glycocalyx, exopolysaccharide (EPS), slime layer
22
Q
Capsule is composed of
A
complex polysaccharides, simple sugar, or D-glutamic acid
23
Q
O antigen
A
LPS
24
Q
K antigen
A
capsule formed from simple sugar, complex polysaccharide, or D-glutamic acid
25
Biofilm
complex, 3-D structure, microcolony of bacteria or yeast, enmeshed in a mucoid exopolysaccharide film
26
Biofilm composition
exopolysaccharides and in some cases proteins (amyloid fibers)
27
Phenotypic changes of bacteria in biofilms
non-motile, persist even with antimicrobials, multi-drug resistant
28
the activation of biofilm formation involves
quorum sensing: sensing the density of the population and switching gene expression
29
Re-seeding from biofilm
some cells in the biofilm revert back to normal, therefore even if anti-microbials have been used the infection may return
30
How are cells released from a biofilm and when?
when the amyloid structural protein is broken down by D-A.A. when the situation dictates it
31
Biofilms function
adherence to host tissue and surfaces (surface colonization), protection against antibiotics and desiccation (Drying out)
32
surface colonization of biofilms allow them to
thrive in a moving environment
33
K antigen
capsular antigen
34
O antigen
LPS
35
Do gram positive bacteria have capsules?
They may or may NOT have capsules
36
Do gram negative bacteria have capsules?
They may or may NOT, O antigen + and K antigen - if no capsule, O antigen + and K antigen + is capsule differs from LPS, O antigen + and K antigen - if capsule is an extension of LPS
37
S-Layers
layer lying directly on cell walls, rigid layer with pores of fixed diameter
38
S-Layers are composed of
protein or glycoprotein
39
S-Layers function
resistance to C3b binding (resists complement mediated killing), prevents phagocytosis by PMNs
40
Translocation
passage through human cells to access new sites
41
Genera capable of Translocation
H. flu, S. pyrogenes, M. tuberculosis
42
Paracellular translocation
passage between cells to enter tissues
43
The ability to slide on solid surfaces is associated with
biofilm formation at least with Mycobacterium smegmatis
44
Polypeptides embedded in the lipid bilayer are stabilized by
divalent cations (Ca and Mg) and hydrophobic interactions with fatty acid moiety of phospholipids
45
Which genera of bacteria DO CONTAIN sterols?
Mycoplasma, helicobacter, ehrlichia, Anaplasma spp.
46
Cell membrane characteristics
permeable for transport, specific transport mechanisms for secretion of proteins (6 types), respiratory components, biosynthetic pathways, sensory and osmoregulatory mechanisms and chemotaxis
47
Type III transport system (injectosomes)
conserved multiprotein system that pathogenic gram-NEGATIVE bacteria use to insert protein toxins into cells
48
Respiratory components found in the cell membrane
ETC, ATP synthase, generating proton motive force
49
Cell membrane contains components for biosynthesis of
cell wall, cellular replication (septal ring)
50
The cell wall regulates osmotic pressure, such that the bacterial cell is ____________ compared to the environment
hypertonic
51
Chemotaxis mechanisms lie within the
cell membrane
52
The peptidoglycan layer in the gram positive cell wall is much ______ than the gram negative cell wall
thicker
53
Describe the peptidoglycan layer of the cell wall of gram-positive cells
thick peptidoglycan layer, covalently linked polysaccharides, lipoteichoic acid extend through the peptidoglycan layer, no outer LPS layer
54
Describe the peptidoglycan layer of the cell wall of gram-negative cells
thin peptidoglycan layer, no covantely linked polysaccharides or LA extending through, contains an outer layer of LPS, located within the periplasm
55
Cell wall function
maintain cell shape, shield from environment, virulence and toxicity factors
56
What portion of the cell wall is important in maintaining cell shape and providing mechanical strength
peptidoglycan layer
57
What portion of the cell wall determines the gram staining
peptidoglycan layer
58
Peptidoglycan layer composition
woven network of NAG and NAM (N-acetylmuramic acid and N-acetylglucosamine)
59
Lysozyme
cleaves the amino sugar bonds (NAM, NAG) of the peptidoglycan layer, lysing the bacteria
60
Where is lysozyme found
saliva and tears
61
Peptide stems allow for
(amino acid side chains) weaving/covalent linking of the NAM and NAG molecules of the peptidoglycan layer
62
Peptide side chains of NAM and NAG must contain
D-A.A.
63
Peptidoglycan layer functions
prevents cell bursting from osmotic forces, gives cell shape
64
Which bacteria lack peptidoglycan
Mycoplasma, Rickettsia, Ehrlichia, Anaplasma
65
Outer cell membrane is
a lipid bilayer with phospholipid as the inner leaflet and LPS as the outer leaflet
66
Periplasm
found outside the cell membrane of gram negative bacteria and contains the peptidoglycan layer
67
Periplasm function
1. OSMOTIC PROTECTION
| nutrient uptake from OM to CM, chemotaxis, degradative enzymes, osmoregulation
68
Are Gram-negative bacterium more or less susceptible to cell-wall active agents?
less; only 1 layer of peptidoglycan which is hidden in the periplasm beneath the outer membrane
69
Outer Membrane functions
1. SHIELDS AGAINST ENVIRONMENTAL CHANGES,
virulence and toxicity factors, antigenic components, receptors for antibodies and sex pilus, anchors external structures of bacteria
70
Outer Membrane prevents entrance of
dyes, detergents, hydrolytic enzymes (lysozome)
71
Outer membrane composition
lipopolysaccharide, phospholipid, proteins
72
The outer leaflet of the outer membrane lipid bilayer
LPS
73
The inner leaflet of the outer membrane lipid bilayer
phospholipid
74
Porins
Outer membrane proteins that form aqueous channels to allow hydrophilic substances pass through the OM
75
LPS constituents
Lipid A + core + O-antigenic chain
76
Lipid A is composed of
fatty acid + disaccharide, phosphate groups, fatty acids, LPS toxicity is associated with Lipid A
77
Core is composed of
oligosaccharides, sugars, ketodeoxyoctulonate [KDO] - common in enteric bacteria
78
Terminal Polysaccharide
O antigen
79
Terminal Polysaccharide is composed of
sugars, a unit repeating, highly specific and highly variable
80
Terminal polysaccharide variation
each strain of bacteria possesses a chemically distinct O-antigen
81
Lipooligosaccharide (LOS) is composed of
Lipid A + extended core
82
Lipooligosaccharide (LOS) is
synthesized in place of LPS in Neisseriameningitidis and N. gonorrhoeae, and H. flu and H. ducreyi
83
Lipooligosaccharide (LOS)
lacks O-antienic chain
84
LPS functions
structural component of OM, pyrogen, complement pathway, hageman factor, release of endogenous mediators
85
LPS acts as a pyrogen by producing
induction of IL-1 which acts on the hypothalamus, or DIRECTLY acting on the hypothalamus
86
LPS activates __________ complement pathway
alternative
87
LPS activates ___________ factor
Hageman (factor XII)
88
LPS induces the release of endogenous mediators:
TNF-alpha, IL-1, IL-6, arachidonic metabolites, bradykinin, histamines, NO, free radicals
89
LPS structure is
heat stable unless with strong oxidizers
90
LPS does not form
toxoids, due to to heat stability
91
How would one detoxify LPS?
burning or oxidation
92
LPS may potentially cause
SIRS; with macrophages, PMNs, and endothelial cells as effector cells
93
Bacterial endospore-formers
Clostridium and Bacillus
94
Activation of the SIRS pathway occurs via
infection (esp gram-negative bacteria) or non-infectious etiology
95
How does LPS activate SIRS immune response
LPS binds LBP, LBP-LPS complex binds membrane-bound CD14 on PMNs, macrophages, and monocytes to and activates TLR; complex interacts with soluble CD14 which causes endothelial leakiness (hypotension, edema)
96
ARDS (acute respiratory distress syndrome) is a common feature of _________, not _________
distributive shock, not systemic inflammatory response syndrome
97
Endogenous mediators released by activation of TLR result in
temperature > 38 or < 36
HR >90
RR >20
Leukocytosis >12,000 or leukopenia <4000
98
The clinical definition of SIRS is
```
TWO or MORE symptoms:
temperature > 38 or < 36
HR >90
RR >20
Leukocytosis >12,000 or leukopenia <4000
```
99
SIRS consists of
ONE or MORE
Systemic inflammation/ "hyperinflammatory state"
Activation of coagulation
Inhibition of fibrinolysis
100
Why does activation of coagulation occur in SIRS?
LPS activation of Hageman Factor XII, activates clotting system and fibrinolysis, followed by inhibition of fibrinolysis by plasminogen activator inhibitor
101
plasminogen activator inhibitor
causes inhibition of fibrinolysis during SIRS
102
DIC Disseminated Intravascular Coagulation
results from accumulation of undissolved thrombin in the microcirculation
103
DIC may lead to
multi organ failure and purpuric skin lesions
104
Survival of the hyper inflammatory state is followed by
hypo inflammatory state "immunoparalysis"
105
Hypoinflammatory state is manifested by
loss of delayed hypersensitivity
failure to clear primary infection
development of secondary infection
reactivated dormant viruses
106
Sepsis is defined by
the presence of BOTH:
- A proven infection
- Presence of 2 or more SIRS manifestations
107
Severe sepsis is defined by
the presence of BOTH:
- Sepsis
- Organ Failure
108
Septic Shock is defined by
the presence of BOTH:
- Severe sepsis
- refractory hypotension (40-50/30-40)
109
Shock is defined by
inadequate perfusion of tissues
110
3 Types of shock
cardiogenic, vascular obstructive, hypovolemic
111
Distributive shock is a type of
hypovolemic shock
112
Distributive shock consists of
endothelial cell dysfunction (leakiness), loss of vascular resistance --> hypotension, coagulopathy/DIC, septic cardiomyopathy --> reduced CO (reversible)
113
Septic cardiomyopathy is induced by
LPS, C5A, IL-1beta, TNF-alpha, IL-6
114
Clinical manifestations of distributive shock
fever or hypothermia, chills, leukopenia or leukocytosis, high HR and RR, DIC, hypotension shock and DIC can lead to MOF or MOD
115
Therapy for early Sepsis - sepsis resuscitation bundle
Measure serum lactate, obtain blood specimen for culture, administer broad-spectrum antibiotics, if hypotensive administer fluids or vasopressin, achieve O2 saturation
116
Therapy for early Sepsis - sepsis management bundle
corticosteroids, tight glycemic control
117
Failed sepsis therapies
anti-TLR4 (eritoran tatrasodium) and drotecogin alfa (activated, recombinant protein C)
118
Detecting LPS in pharmaceutical industry
Limulus amebocyte lysate test, mAb anti-LPS
119
endotoxin v exotoxin - chromosome encoded?
endotoxin only chromosome encoded, exotoxin may be encoded by chromosome or plasmid
120
endotoxin v exotoxin - required for survival?
endotoxin - yes; exotoxin - no
121
endotoxin v exotoxin - composition?
endotoxin - sugar-phosphate-fatty acids
| exotoxin - protein
122
endotoxin v exotoxin - number encoded by bacteria?
endotoxin - more than 1 structural form
| exotoxin - one specific form
123
endotoxin v exotoxin - toxoid?
endotoxin - NO, heat stable
| exotoxin - YES, heat labile
124
endotoxin v exotoxin - receptor?
endotoxin - general PAR receptor
| exotoxin - specific toxin receptor
125
endotoxin v exotoxin - mechanism?
endotoxin - systemic reaction > SIRS > DS
| exotoxin - host cell reaction of altered function, lysis, molecule mimicry
126
endotoxin v exotoxin - pyrogens
endotoxin - exogenous (direct through BBB) and endogenous pyrogen (IL-1, TNF-alpha)
exotoxin - no
127
endotoxin v exotoxin - presence in human blood
endotoxin - sepsis
| exotoxin - toxemia
128
name the main components of the gram-positive cell wall
peptidoglycan, teichoic acid, lipoteichoic acid (in outer CM leaflet)
129
Peptidoglycan in gram positive bacteria
extensively cross-linked (muramic side chains) and present in large amounts
130
Lipoteichoic acid structure
glycerol-PO4 or ribitol-PO4 covalently linked to glycolipid, noncovalently linked to outer leaflet of CM, extending through the peptidoglycan to the external environment
131
What is the primary factor in the adhesion of Strep pyrogenes to fibronectin on pharyngeal epithelial cells
Lipoteichoic acid
132
Teichoic acid structure
glycerol-PO4 or ribitol-PO4 covalently linked to peptidoglycan, extending through the peptidoglycan to the external environment
133
Teichoic acids medical importance
peptidoglycan + teichoic acid can produce endotoxin-like shock in patients with staph. aureus by interacting with C-reactive protein and activating the alternative complement pathway
134
How can DIC and DS occur with pathogens lacking LPS?
PARS recognition of PAMPS, releasing endogenous mediators that cause SIRS
135
NOD1 and NOD2
internal PAR, NOD2 deficiency is related to Crohn's
136
TLR
extracellular PAR, bind peptidoglycan, teichoic acid, N-f-met-leu-phe, CpG, LPS
137
Spores
a complete but inactive cell in a protective shell, forms inside mother cell which dies
138
Most bacteria __________ form spores
DO NOT
139
Spores are formed in order for bacteria to
survive adverse conditions until environmental conditions are favorable
140
bacterial endospores have increased
longevity, resistance to heat/temp, resistance to desiccation, resistance to chemical agent
141
What 2 genera of bacteria are spore-forming
bacillus and clostridium
142
Small colony variants
growth-deficient variants that fem colonies, due in part to deficiencies in energy metabolism, possess enhances resistance to antibiotics, recurrent infections
143
small colony variants are formed by
Staphylococcus aureus, pseudomonas aeruginosa, E. coli and UTIs
144
Small colony variants are associated with chronic, recurrent infections of
heart,lung, bones, urinary tract
145
Biofilm and SCV are phenotypic switching, meaning
they can revert back to their previous form and re-seed
