Lecture 5 and 6 Flashcards
1
Q
What is a flagella?
A
A filamentous protein structure attached to the cell surface that provides a swimming movement
2
Q
How do flagella in prokaryotes differ from eukaryotes?
A
The lack the 9+2 arrangement of microtubules
The way they are powered
3
Q
What is the diameter of a prokaryotic flagella?
A
20 nanometers
4
Q
How are bacterial flagella powered?
A
By a proton motive force established on the bacterial membrane
5
Q
How are eukaryotic flagella powered?
A
ATP hydrolysis
6
Q
Why are very few cocci motile?
A
They are adapted to dry environments so lack hydrodynamic design
7
Q
What are the several distinct proteins that make up the flagellar apparatus?
A
Basal body, hook structure, flagella filament
8
Q
What is the structure of the basal body?
A
A system of rings embedded in the cell envelope
9
Q
What name is given to the shape of bacterial flagella?
A
Helical
10
Q
How is a flagella different to fimbria and pili?
A
They are longer and thicker
11
Q
What name is given to bacteria with no flagella?
A
Atrichous
12
Q
What name is given to bacteria with flagella distributed all over the bacterial surface?
A
Peritrichous
13
Q
What name is given when flagella are distributed at one or both ends of the bacteria?
A
Polar
14
Q
What are the two names given to describe the number of polar flagella?
A
Monotrichous- one flagellum
Lophotrichous- multiple flagella
15
Q
What name is given to describe the distribution of polar flagella?
A
Amphitrichous- flagella at either end
16
Q
What is the filament of the flagella composed of?
A
Flagellin (globular protein)
17
Q
How is flagellin arranged?
A
In intertwining chains to form a hollow tube
18
Q
What is the purpose of the hook?
A
It is a connector region between filament and basal body
19
Q
What is the hook composed of?
A
Flagella hook protein
20
Q
What does the hook act as?
A
A universal joint
21
Q
What does the basal body consist of?
A
A small central rod inserted into a series of rings
22
Q
What does the basal body function as?
A
A motor, also anchors flagella to cell wall and plasma membrane
23
Q
What do gram negative bacteria have in their basal bodies?
A
2 pairs of rings, the outer anchored to cell wall and inner to plasma membrane
24
Q
What do gram positive bacteria have in the basal bodies?
A
Inner pair of rings anchored to plasma membrane
25
In what direction do flagella rotate?
Both clockwise and anticlockwise
26
What is interesting about the speed a flagella can be rotated?
It can be altered (200-17,000 rpm)
27
What name is given to movement in one direction of a bacteria?
A run, or swim
28
What name is given to the change in direction that interrupts runs?
Tumbles
29
What is it called when cells move towards favorable or away from adverse environment?
Taxis
30
Name two type of taxis.
Chemotaxis
| Phototaxis
31
What names are given to positive and negative taxis stimulus?
Attractant and repellant
32
When does the frequency of tumbles increase?
When bacteria are moving away from repellent stimulus
33
What is an axial filament?
A modified flagellum (endoflagella) that is enclosed in space between outersheath and cell wall
34
Name two examples of spirochete bacteria with axial filaments.
Treponema pallidum- syphilis
| Borrelia burgdoferi- lyme disease
35
Where is one end of the axial filament attached?
Near to polar of cell
36
What does rotation of the axial filament cause?
Corkscrew-type movement
37
What is the plasma membrane?
A barrier that separates the cytoplasm from the environment
38
How thick is the plasma membrane?
6-8nm
39
Where are photosynthesis complexes found on the plasma membrane of bacteria?
Folds called thylakoids or chromatophores
40
Name some structures found within the bacterial cytoplasm.
Cytoskeleton, nucleoid, ribosomes, inclusion bodies, endospores
41
Define nucleoid.
Region containing bacterial chromosome
42
Describe the bacterial chromosome.
Generally a singular, circular chromosomes composed of double stranded DNA, not associated with histones
43
What does the shape of the bacterial nucleoid depend on?
Where the cell is within the cell cycle
44
Why is the chromosome attached to the cell membrane?
Cell membrane proteins responsible for DNA replication and segregation
45
When a cell is actively dividing, how many ribosomes may they have?
10,000+ ribosomes per cell
46
What structures give the cytoplasm a granular appearance?
Ribosomes
47
What do ribosomes consist of?
Two subunits made of proteins and rRNA
48
Why is the difference between the 70s ribosome and 80s ribosomes significant?
Difference can be exploited in terms of drug development to block protein production in bacteria
49
Give examples of the bacterial ribosome being targeted by antibiotics.
Steptomycin and gentamicin bind to 30s subunit
| Erthromycin and chloramphenicol bind to 50s subunit
50
What is the function of inclusion bodies?
Energy reserves or resevoirs of structural building blocks
51
What are inclusion bodies?
Aggregates of specific material (s) that are not membrane bound
52
What name is given to the reserve of high energy, inorganic phosphate?
Metachromatic granules (volutin)
53
Give an example of a bacteria that has volutin inclusion bodies.
Corynebacterium diphtheriae
54
What name is given to the reserve of carbon (not lipid)?
Polysaccharide granules (starch/glycogen)
55
What name is given to the lipid reserve of carbon?
Polyhydroxybutyrate (PHB)
56
Give an example of a bacteria that has polysaccharide granule reserves.
E. coli
57
Give an example of types of bacteria that have polyhydroxybutyrate reserves.
Mycobacterium, Bacillus
58
Name another type of molecule that can be stored in inclusion bodies.
Sulphur granules
59
Name two types of bacteria that store sulphur granules.
Purple and green sulfur bacteria
60
What structures do bacteria have that compartmentalize bacterial processes?
Microcompartments
61
What are microcompartments?
Non-membrane, organelle like protein shell structures surrounding enzymes, proteins and gas
62
Give an example of microcompartments filled with enzymes.
Carboxysomes
63
What is the shape of carboxysomes?
Polyhendral shape
64
In what type of bacteria are carboxysomes commonly found?
Many autotrophic bacteria
65
What is the long name for rubisco?
Ribulose 1,5-diphosphate carboxylase
66
What do carboxysomes contain?
Rubisco
67
What shape are gas vacuoles?
Hollow cylinders
68
In what type of bacteria are gas vacuoles commonly found?
Aquatic bacteria such as cyanobacteria
69
Why is adjusting buoyancy important?
To be able to move up and down the bacteria column to be able to photosynthesize.
70
What type of intracellular structure might be found in magnetic responsive bacteria?
Magnetosomes
71
What type of magnetic substance is commonly found in magnetosomes?
Iron oxide (magnetite)
72
What is the purpose of magnetosomes?
Can be used to orientate and migrate bacteria along geomagnetic lines field lines
73
What is the structure of a magnetosome?
Membranous
74
What is the barrier between the lumen of the microcompartment and the cytosol formed of?
Conserved families of proteins assembled into a selectively permeable shell
75
How many structural groups of shell proteins are there that make up microcompartment shells?
3
76
Give an example of bacterial microcompartments being adapted for bioengineering in plants.
Enhancing CO2 fixation by installing carboxysomes in chloroplasts
77
What are some other potential applications for engineered microcompartments?
Serving as nano-factories for biochemical production, or as novel drug delivery devices
78
What type substance stored in a microcompartment may be toxic to certain insects?
Parasporal crystals
79
Name a bacteria that has magnetosomes.
Magnetospirillum spp and several gram negative bacteria
80
Name a bacteria that produces parasporal crystals.
Endospore-forming Bacillus
81
How can parasporal crystals be potential exploited?
As insecticides.
82
What is an endospore?
A dormant, tough, non-reproductive structure produced by some bacteria to ensure survival through periods of environmental stress
83
In what bacteria are endospores found?
Some gram positive bacteria (Bacillus, Clostridium)
84
How are endospores dispersed?
Wind, water, animal gut
85
What is the name given to endospore formation?
Sporulation
86
What is the name given to the return to vegetative state from endospore?
Germination
87
When does sporulation occur?
When key nutrients become scarce/unavailable (environmental stress)
88
How long does it take for sporulation to occur?
Several hours
89
What is the first step in sporulation?
Newly replicated chromosome and some cytoplasm become isolated by ingrowth of plasma membrane (spore septum)
90
What happens after the replicated chromosome has become isolated?
The mother cell engulfs the spore, double layed membrane surrounds the chromosome and cytoplasm, creating a forespore
91
What happens to the newly formed forespore?
A thick layer of peptidoglycan is laid down between the 2 membranes
92
What happens after the peptidoglycan is laid down between the two membranes?
Spore coat (made of protein) is laid down around the outermembrane, forming endospore. Cytoplasm of endospore becomes dessicated.
93
What is important about the shape and position of an endospore?
It varies in different species, so is useful for classification and identification purposes.
94
Name the three types of position of an endospore.
Terminal spores, subterminal spores, central spores.
95
What are the three distinct phases of endospore germination?
Activation, germination, outgrowth
| rapid, takes few minutes
96
How can activation of endospores occur?
Heating activated spores conditioned to germinate
97
What occurs during germination?
In the presence of nutrients (amino acids- alanine) spore becomes metabolically active
98
What occurs during outgrowth of endospores?
Uptake of water, RNA, DNA protein synthesis begins, vegetative cell emerges
99
What 4 structures are found in all bacteria?
Cytoplasm, ribosomes, plasma membrane, nucleoid
100
What is a cell wall?
A complex, semi-rigid structure that maintains cell shape
101
How is the cell wall related to osmosis?
Prevents osmotic lysis of cell
102
What is another function of the cell wall?
To serve as an attachment point for appendages such as flagella, pili, fimbri etc.
103
What is a major component of bacterial cell walls?
Peptidoglycan
104
What are the two alternating sugars that peptidoglycan consists of?
N-acetyglucosamine (NAG or G)
| N-acetylmuramic acid (NAM or M)
105
How are NAG and NAM connected?
By a Beta-1,4 glycosidic bond
106
What are 2 amino acids that peptidoglycan is made of?
Lysine, diaminopimelic acid (DAP)
107
What is attached to N-acetylmuramic acid?
A peptide chain of three to five amino acids, which can be cross-linked to the other peptide chain of another strand
108
What is unusual about the amino acids found in the cell wall of bacteria?
They can alternate between L- and D- forms (only L-form amino acid are used in proteins)
109
What enxyme can break the B1-4 linkages?
Autolysins (found in lysozome)
110
What aspect of cross linking varies between species?
The degree of cross linking
111
How does cross linking effect the cell wall?
Provides strength, more cross linking = greater rigidity
112
What name is given to the peptide chains linking directly between each glycan backbone?
Transpeptidation
113
What name is given to a bridge that can connect peptide chains indirectly?
Pentapeptide bridge
114
What effect does pentapeptide bridges have on the cell wall?
Makes the cell wall more flexible
115
What is the structure of a pentapeptide bridge?
5 gly amino acids
116
Give an example of a bacteria that has a pentapeptide bridge in its cell wall.
Staphylococcus aureus (gram positive)
117
Give an example of a bacteria that has transpeptidation.
Escherichia coli (gram negative)
118
What antibiotics stops the formation of cross links in bacterial cell walls?
Beta-lactam antibiotics, such as penicillin and cephalosporins
119
How do beta-lactam antibiotics stop cross link formation?
They inhibit transpeptidase
120
What does transpeptidase do?
Catalyses the formation of the final bond between two peptide chains (transpeptidation)
121
How thick is the peptidoglycan layer in gram negative bacteria?
2-5nm
122
How thick is the peptidoglycan layer in gram positive bacteria?
Up to 25nm
123
How much of the cell wall is made up of peptidoglycan in gram positive bacteria?
90%
124
What else can be found in the petidoglycan layer of many gram positive bacteria?
Teichoic acids (glycopolmers)
125
What are the two parts of a teichoic acid?
Disaccharide linkage unit
| Main chain polymer
126
What is the structure of the disaccharide linkage unit in teichoic acids?
N-acetylmannosamine beta(1,4) bonded to N-acetylglucosamine-1-phosphate
127
How conserved is the disaccharide linkage until across bacteria species?
Highly conserved
128
What is the structure of the main chain polymer in teichoic acids?
Glycerophosphate or ribitol phosphate polymer which binds to sugars and D-alanine
129
What properties do main chain polymers of teichoic acids have?
Zwitterionic properties (+ and - electrical charge)
130
How conserved are main chain polymers in teichoic acids across bacterial species?
Not conserved
131
What are the two types of teichoic acid?
```
Lipoteichoic acid (LTA)
Wall teichoic acid (WTA)
```
132
What is a lipoteichoic acid?
The disaccharide linkage unit attaches to diacylglycerol in the cell membrane
133
What does lipoteichoic acid interact with?
The main chain polymer interacts with petidoglycan
134
What does the linkage unit of wall teichoic acid bind with?
N-acetylmuramic acid in the petidoglycan chain
135
What happens to a cell without teichoic acid?
It dies
136
What is the function of teichoic acid?
Still unknown, could attract cations/anions (gives rigidity to cell wall or regulate their movement), could regulate blastosomes
137
What does the main chain of a WTA interact with?
Peptidoglycan and into the surrounding environment
138
What is pathogenesis?
The manner of development of a disease
139
How are teichoic acids involved in pathogenesis?
They promote adherence to host tissues
140
Give an example of teichoic acids promoting adherence to host tissues.
Mediate attachment of staphylocicci to mucosal cells
141
How can teichoic acid induce spetic shock?
They can promote injury/damage to organ, causing low blood pressure
142
What is another importance of teichoic acid in medicine?
Suspected ligands for toll-like receptors
143
Where are toll-like receptors found?
On cells (e.g. macrophages/dendritic cells) of the immune system
144
What can teichoic acid do to toll-like receptors?
Trigger innate immune response and development of antigen-specific acquired immunity
145
As a general rule, are gram negative or gram positive bacteria better at getting into our bodies?
Gram negative
146
What percentage does peptidoglycan make up of the outermembrane of gram negative bacteria?
10%
147
Where is the peptidoglycan layer found in gram negative bacteria?
In the periplasm- between outer and plasma membrane
148
How wide is the periplasm?
15nm
149
What is the periplasm?
Gel-like fluid containing degradative enzymes, binding proteins, chemoreceptos, detoxifying enzymes
150
Name three degradative enzymes found in the periplasm.
Phosphatatses (degrade phosphate containing compounds)
Proteases (degrade proteins/peptides)
Endonucleases (degrade nucliec acid)
151
Name a detoxifying enzyme found in the periplasm.
Beta-lactamase- degrades Beta-lactam antibiotics
152
What does the outermembrane of gram negative bacteria contain?
Lipopolysaccharides, lipoproteins, phospholipids
153
What is the role of the outermembrane in gram negative bacteria?
Aids in evading phagocytosis, acts as a barrier to antibiotics, enzymes, detergents, heavy metals, bile salts, dyes, and prevents molecules in periplasm being lost
154
What name is given to transporter proteins in the outermembrane of gram negative bacteria?
Porins (can be specific and non-specific)
155
What is embedded in the top layer of the outermembrane of gram -ve bacteria?
Lipopolysaccharides
156
What do lipopolysaccharides do?
Stabilise outer membrne, increase negative charge, protect from chemical attack
157
What three main parts do lipopolysaccharides consist of?
Lipid A
Core polysacchairde
O-polysaccharide
158
What does lipid A consist of?
Phosphorylated glucosamine disaccharide and fatty acids
159
What do the fatty acids in lipid A do?
Anchor LPS into the outermembrane
160
What else does lipid A function as?
An endotoxin- released when gram negative bacteria die and are degraded
161
What do endotoxins do?
Elicit symptoms associated with infection- fever, blood vessel dilation, vomit, diarrhoea, blood clotting
162
What does the core polysaccharide of LPS contain?
Sugars
163
What is the role of the core polysaccharide in LPS?
Structural role, provides stability, role varies between species.
164
What else is the O-polysaccharide known as?
O-antigen or O-chain
165
What is the O-polysaccharide made of?
Repetitive sugar polymer
166
What are the two types of O-chains found in bacteria?
Long O-chains (Smooth LPS)
| Shorter O-chains (rough LPS)
167
What do O-chains do?
Prevent hydrophobic molecules from getting to outer membrane surface
Extend into the external environment
Function as antigens
168
What are some bacteria with rough LPS more susceptible to?
Hydrophobic drugs
169
Do O-chains vary?
Greatly between bacterial species and strains (e.g. 160 in E.coli)
170
How are O-chains useful in medicine?
Distinguishing between strains of the same species
171
Name a strain of E.coli.
E coli O157:H7
172
What does E coli O157:H7 cause?
Enteroheamorrhagic fever
173
What does H7 mean?
The strain of flagelar antigen
174
When was the gram stain test developed and by who?
1884
| Christian Gram
175
What is the first step of the gram stain test?
Heat fixed cells treated with primary stain, crystal violet
176
What is the second step of the gram stain test?
The stain is washed off and the smear treated with a mordant (iodine)
177
What does mordant mean?
A substance that combines with a dye or stain and fixes it in a material
178
What happens to cells after the are treated with iodine?
The cells are washed with a decolourising agent (alcohol)
179
What happens to the cells after they are treated with alcohol?
The smear is counterstained with safranin and observed under the microscope
180
Name two mycobacterium.
Mycobacterium tuberculosis
| Mycobacterium leprae
181
Describe the cell wall of mycobacterium.
Cell wall contains thin layer of peptidoglycan, surrounded by mycolic acid
182
What is mycolic acid?
Hydrophobic, waxy lipid (hence can't be stained, and also repels antibiotics)
183
How can mycobacterium instead be stained?
With carbolfuchsin which binds to components of the cytosol after the cells are heated to make mycolic acid more pliable
184
Name some wall-less bacteria.
Mollicutes (mycoplasma)
185
How are mycoplasma bacteria protected?
Their plasma membrane contains sterols which give rigidity and protect the cell from lysis
186
What is a glycocalyx?
A viscous, gelatinous polymer surrounding the cell secreted by most bacteria
187
What is the glycocalyx composed of?
Polysaccharides and/or protein, composition varies within a species
188
What are the two types of glycocalyx?
Capsule, slime layer
189
How do capsules and slime layers vary?
Capsule is well organised and firmly attached to cell wall, slime layer is unorganised and loosely attached to cell wall
190
How are glycocalyx and biofilms associated?
The glycocalyx assists in the attachment to surfaces
191
What bacteria can adhere to teeth?
Steptococcus mutans
192
What bacteria can adhere to the small intestine?
Vibrio cholera
193
What bacteria can adhere to and colonise the respiratory tract?
Klebsiella
194
The glycocalyx can also help in the evasion of...
the immune system (phagocytosis)
195
The glycocalyx helps resist ______ (the loss of water)
desiccation
196
How can the glycocalyx aid nutrient supply?
It can be degraded and the sugars used as an energy source.
| Viscosity can prevent loss of nutrients
197
What is one more function of the glycocalyx?
Facilitate cell to cell communication by acting as a medium for chemical signalling
198
What are fimbriae?
Short, stiff, hair-like proteinaceous appendages found predominantly in gram negative bacteria
199
Where are fimbriae found and how many are there?
At poles or along entire surface (rods have them at poles)
| Few to several hundred
200
What do fimbriae do?
Stick cells to each other and to surfaces, such as during biofilm formation (colonization can occur)
201
Give an example of fimbriae adhering to surfaces.
In E.coli O157:H7, when fimbriated, it adheres to lining of small intestine
202
What are pili?
Hair-like, proteinacrous appendage, longer than fimbriae, only 1 or 2 per cell
203
What are 3 functions of pili?
Adherence to surfaces, motility, sex (conjugative pili)
204
How do type IV pili enable motility?
Synthesis of pili until it reaches surface, retraction as it is dismantled.
Twitching motility- short, jerky, intermittent motion
Gliding motility
