Chapter 3 part 2 Flashcards
1
Q
The differences in arrangement of the cell wall in prokaryotic cells distinguish what?
A
Differences in the arrangement of cell walls of prokaryotic cells distinguish two main groups of bacteria:
- Gram positive
- Gram negative
2
Q
Gram positive
A
Bacteria that have a cell wall characterized by a thick layer of peptidoglycan
3
Q
What color when gram stained does gram positive cells turn?
A
Purple
4
Q
Gram negative
A
Bacteria that have a cell wall characterized by a thin layer of peptidoglycan surrounded by an outer membrane
5
Q
When gram stained, what color do gram negative bacteria turn?
A
Pink
6
Q
Peptidoglycan
A
Strong mesh like material found only in bacteria.
A macromolecule that provides strength to the cell wall
7
Q
Basic structure of peptidoglycan
A
Alternating series of two major subunits related to glucose: NAM and NAG.
These subunits are covalently joined to one another to for, a linear polymer called glycan chain, which serves as backbone of the peptidoglycan molecule.
8
Q
NAM
A
N-acetylmuramic acid
9
Q
Tetrapeptide chain
A
What is attached to each NAM molecule.
Is a string of 4 amino acids.
Play an important role in strength of peptidoglycan.
10
Q
NAG
A
N-acetylglucosamine
11
Q
Two major subunits related to glucose?
A
- NAG
- NAM
12
Q
Glycan chain
A
What forms when NAG and NAM are covalently joined to one another.
Serves as backbone of the peptidoglycan molecule
13
Q
Backbone of peptidoglycan molecule
A
Glycan chain
14
Q
How are adjacent glycan chains cross linked?
A
Two tetrapeptide chains can connect to one another.
15
Q
How do gram negative bacteria peptidoglycan differ from gram positive peptidoglycan?
A
In Gram negative bacteria, the connection between tetrapeptide chains is direct, whereas in Gram positive bacteria, the connection is usually via a peptide interbridge (series of amino acids)
16
Q
Peptide interbridge in gram positive peptidoglycan
A
Is a series of amino acids.
17
Q
Gram positive cell wall is characterized by…
A
A relatively thick layer of peptidoglycan
18
Q
As many as how many interconnected glycan chains make up the polymer in gram positive peptidoglycan?
A
As many as 30 layers.
19
Q
What can pass through gram positive peptidoglycan?
A
Many small substances including sugars and amino acids.
20
Q
Teichoic acids
A
Gram positive cell wall component, composed of chains of a common subunit, either ribitolphosphate or glycerol-phosphate, to which various sugars and D-alanine are usually attached.
21
Q
How are teichoic acids on the cell?
A
Some teichoic acids are covalently joined to and extend above the peptidoglycan layer, and others are linked to the cytoplasmic membrane.
22
Q
Periplasm
A
Gel like substance sandwiched between the cytoplasmic membrane and the peptidoglycan layer of at least some gram positive bacteria.
23
Q
Gram negative cell wall contains…
A
Only a thin layer of peptidoglycan.
24
Q
Outer membrane
A
A unique lipid bilayer embedded with proteins.
25
How is the outer membrane joined to peptidoglycan
By lipoproteins
26
Outer membrane (in prokaryotes)
The unique lipid bilayer of gram negative cells that surrounds the peptidoglycan layer
27
Outer membrane (in eukaryotes)
The membrane on cytoplasmic side of the organelles that have double membranes.
28
Lipopolysaccharide (LPS)
Molecule that makes up the outer layer of the outer membrane of gram negative bacteria.
29
What happens when LPS is injected in animals?
It causes fever and other symptoms characteristic of infections by live bacteria.
30
Why do symptoms arise when injected with LPS?
The symptoms arise from the body’s response to LPS, a molecule the body’s defense systems use as an indication that gram negative bacteria have invaded.
31
Why is LPS called an endotoxin?
Because when significant amounts of LPS spread throughout the body, the response can be deadly. Because of this lethal effect, LPS is called endotoxin.
32
Endotoxin
The LPS component of the outer membrane of gram negative
33
What is responsible for the toxic properties of LPS?
Lipid A
34
What 2 parts of the LPS molecule are particularly notable?
1. Lipid A
2. O Antigen
35
Lipid A
anchors the LPS molecule in the lipid bilayer.
Is the portion of the LPS molecule that body recognizes as the sign of invading Gram-negative bacteria.
36
O-Antigen
Is the part of LPS directed away from the membrane, at the end opposite Lipid A.
It is made up of a chain of sugar molecules, the number and type of which vary among different species. The differences can be used to identify certain species or strains.
37
Why are Gram negative bacteria generally less sensitive to many medications?
Like the cytoplasmic membrane, the outer membrane serves as a barrier to the passage of most molecules. It keeps out many compounds that could damage the cell, including certain antimicrobial medications.
38
Porins
Proteins in the outer membrane of Gram-negative bacteria that form channels through which small molecules can pass.
39
Periplasmic space
region between the cytoplasmic membrane and the outer membrane.
40
Periplasm
Fills the region between the cytoplasmic membrane and the outer membrane of Gram-negative bacteria and the cytoplasmic membrane and peptidoglycan layer of at least some Gram-positive bacteria.
41
The most thoroughly studied of a group of antibiotics that interfere with peptidoglycan synthesis.
Penicillin
42
Penicillins
Group of antibiotics that includes penicillin and that interferes with the synthesis of the peptidoglycan portion of bacterial cells walls.
43
How does penicillin function?
it functions by preventing the cross-linking of adjacent glycan chains (it inhibits enzymes that normally catalyze the cross-linking step).
44
Lysozyme
Enzyme that degrades the peptidoglycan layer of the bacterial cell wall.
Breaks the bonds that link the alternating subunits of the glycan chains.
45
Penicillinase
An enzyme that degrades penicillin.
46
Antibacterial Substances that Target Peptidoglycan
1. Penicillin
2. Lysozyme
47
Mycoplasma species
Causes a mild form of pneumonia
Are flexible because they lack a rigid cell wall
48
How do penicillin and lysozyme effect mycoplasma species?
Neither penicillin nor lysozyme affect these organisms.
49
How do mycoplasma species survive?
Mycoplasma and related bacteria can survive without a cell wall because their cytoplasmic membrane has sterols in it, making it stronger than that of most other bacteria.
50
Why do archaea have a variety of cell wall types?
Probably due to the fact that they inhabit a wide range of environments, including some that are extreme.
51
Pseudopeptidoglycan
a molecule similar to peptidoglycan.
is found in archaeal cell wall
52
Components of pseudopeptidoglycan?
????????? page 56 ??????????
53
Capsule
a distinct and gelatinous layer
54
Slime Layer
is diffuse and irregular material that surrounds some microorganisms
55
Glycocalyx
Polysaccharide layer that surrounds some cells and generally functions as a mechanism of either protection or attachment.
Most capsules and slime layers are composed of polysaccharides and are commonly referred to as glycocalyx.
56
What do capsules and slime layers allow bacterial cells to do?
Some capsules and slime layers allow bacterial cells to adhere to specific surfaces, including teeth, rocks and other bacteria.
Once attached, the cells can grow as a biofilm.
57
Biofilm
a polymer encased community of microbes.
forms when capsules and slime layers adhere to specific surfaces.
58
Extracellular Polymeric substances (EPS)
Polymers part of biofilm
Includes material that make up capsules and slime layers.
59
Flagella
long protein structures responsible for most types of bacterial motility.
Are anchored in the cytoplasmic membrane and cell wall and extend out from the cell surface
60
Where are flagella located?
They are anchored in the cytoplasmic membrane and cell wall and extend out from the cell surface.
61
How to flagella function?
Flagella function by spinning like propellers, pushing the cell through liquid much as a ship is driven through water.
62
Different arrangements of flagella
1. Peritrichous
2. Polar
63
Peritrichous
Distribution of flagella all around the cell
64
Polar
A single flagellum at one end of a cell
65
Helicobacter pylori
the bacterium that sometimes causes gastric ulcers, has powerful multiple flagella at one end of the cell, these allow the bacterial cells to penetrate the thick mucous gel that coats the stomach epithelium.
66
Three basic parts of flagella:
1. a basal body
2. a hook
3. a filament
67
The basal body of a flagella
The basal body anchors the structure to the cell wall and cytoplasmic membrane.
68
The hook
Is a flexible curved segment that extends out from the basal body, connecting it to the filament.
69
The filament
- extends out into the external environment
- is made up of identical subunits of a protein called flagellin. These subunits forma a chain that twists into a helical structure with a hollow core.
70
Flagellin
-makeup the filament
-are identical subunits
- are proteins
71
Archaella
Structures Archaea have that are similar to flagella in shape and function.
72
Differences between Archaella and Flagella?
1. Archaella are about half the diameter of flagella and do not have a hollow core.
2. ATP is used as an energy source to power their rotation rather than proton motive force.
73
Chemotaxis
movement of a cell toward or away from a certain chemical in the environment.
74
Example of chemotaxis if cell is around a nutrient:
-if a compound is a nutrient, it may serve as an attractant, causing cells to move toward it.
-
75
Example of chemotaxis if cell is around a toxic compound
- if the compound is toxic, it may act as a repellent, causing cells to move away.
76
Aerotaxis
Used to describe the response of organisms to O2 concentration; organisms that require O2 for growth move toward it, whereas bacteria that grow only in its absence tend to be repelled by it,
77
Magnetotactic
Bacteria that react to the earth’s magnetic field by the process of magnetotaxis.
78
Pili
Cell surface structures that allow cells to adhere to certain surfaces; some types are involved in a mechanism of DNA transfer.
Provide mechanism for attachment to specific surfaces.
79
Thermotaxis
bacteria that move in response to variations in temperature
80
What is referred to as common pili
Fimbriae
81
Phototaxis
Bacteria that move in response to light
82
Fimbriae
Type of pilus that enables cells to attach to a specific surface.
83
Sex pilus
Thin protein appendage required for attachment of two bacterial cells prior to DNA transfer by conjugation.
84
Twitching motility
Characterized by jerking movements.
85
Prokaryotic chromosome
A single, circular double stranded DNA molecule that contains all the genetic information required by a cell, as well as information that may be helpful but not required.
86
Nucleoid
Region of a prokaryotic cell containing the DNA.
87
Plasmid
Have a structure similar to the chromosome, but they are smaller and typically do not encode essential genetic information.
Extrachromosomal DNA molecule that replicates independently of the chromosome.
88
Endospores
A unique type of dormant cell produced by certain bacterial species.
89
Give 2 examples of bacterial species that produce endospores
1. Members of the genera Bacillus
2. Members of the genera Clostridium
90
What are some features of endospores?
They are extraordinarily resistant to damaging conditions including heat, desiccation, toxic chemicals and UV light.
91
Vegetative cell
An endospore that survives harsh treatments (heat, UV, toxic chemicals) and exits the dormant stage to become a typical multiplying cell.
92
Sporulation
Endospore formation
93
How does sporulation start?
Sporulation is a complex sequence of changes that begin when endospore forming bacteria experience limiting amounts of carbon or nitrogen.
The cells sense starvation conditions, which triggers them to begin the 8 hour Sporulation process.
94
5 steps of sporulation:
1. As sporulation begins, the cell stops growing, but it duplicates the DNA.
2. A septum forms, dividing the cell asymmetrically
3. The larger compartment then engulfs the smaller compartment. These two compartments take on different roles in synthesizing the components that will make up the endospore.
4. As developing endospore continues to mature, the smaller compartment develops into what is called the forespore, which will become the core of the endospore. Peptidoglycan containing material is laid down between the two membranes that surround the forespore, forming the core wall and the cortex. Meanwhile, the mother cell makes proteins that will form the outermost layer of the endospore, the sport coat.
5. Ultimately, the mother cell is degrades and the endospore released.
95
Forespore
The smaller compartment that forms during the 4th stage of sporulation.
Will become the core of the endospore.
96
Parts of an endospore:
-spore coat
-cortex
-acid soluble proteins
-core
97
What are light microscopes used in the lab for?
They are routinely used in the lab to observe cell size, shape, and motility.
98
Spore coat
Thought to function as a sieve, excluding molecules such as lysozyme.
99
Cortex
Helps maintain the core in a dehydrated state, protecting it from the effects of heat.
100
Core
The core has a small, acid soluble proteins that bind to DNA, thereby protecting it from damage.
Core is rich in an unusual compound (calcium dipicolinate), which also seems to play an important role in spore resistance.
101
Germinate
Exit the dormant stage; used to describe the behavior of an endospore or other resting cell.
To exit the dormant stage and develop into a vegetative cell.
102
What can trigger an endospore to germinate?
An endospore can be triggered to germinate by a brief exposure to heat or certain chemicals.
103
Steps of Germination
1. An endospore is triggered to exit dormant stage but brief exposure to heat or certain chemicals.
2. Following such exposure, the endospore absorbs water and swells.
3. The spore coat and cortex then crack open, and a vegetative cell grows out. As this happens, the core wall becomes the peptidoglycan layer of the vegetative cell.
104
How long is the process of germination
It is relatively fast compared to sporulation, taking 1-2 hours.
105
Light microscope
Which uses visible light and a series of lenses to magnify objects.
Can magnify images approximately 1000 fold
106
Electron microscope
Microscope that uses electrons instead of light and can magnify images in excess of 100,000x, revealing many fine details of cell structure.
107
Scanning probe microscope
Allows scientists to produce images of individual atoms on a surface.
108
How does a light microscope work?
Light passes through a specimen and then through a series of magnifying lenses before entering the observer’s eyes.
109
What is the most common type of light microscope?
Bright field microscope
110
Bright field microscope
The most common type of light microscope.
It evenly illuminates the field of view and generates a bright background.
111
What is the modern light microscope called
Compound microscope
112
Compound microscope
Microscope that uses multiple magnifying lenses, thereby visually enlarging an object by a factor equal to the product of the magnification of each lens.
113
Objective lens
The lens or series of lenses of a compound microscope that is closest to the specimen.
114
Ocular lens
Lens of a compound microscope that is closest to the eye.
Also called eyepiece.
115
Condenser lens
Lens used to focus the illumination of a microscope; it does not affect the magnification.
Focuses light on a specimen.
116
Where is the condenser lens located?
The condenser lens is positioned between the light source and specimen .
117
Resolution or resolving power
The ability to distinguish two objects that are very close together.
It is defined as the minimum distance between two points at which those points can still be observed as separate objects.
118
What does high resolving power mean
A high resolving power means that details of an image are clearer.
119
The resolving power of a microscope depends on the quality and type of what?
1. Type of lens
2. Wavelength of the light
3. The magnification
4. How the specimen has been prepared.
120
When must immersion oil be used?
To obtain max resolution when using certain high power objectives such as 100x lens, immersion oil must be used to displace the air between the lens and the specimen.
121
What does oil immersion prevent?
This prevents the refraction (bending of light rays) that occurs when light passes from glass to air.
122
Why does immersion oil prevent refraction?
Because immersion oil and glass have the same refractive index, and therefore the light rays are not bent.
123
Contrast
The number of different visible shades in a specimen
Is the difference in color intensity between an object and the background-affects how easily cells can be seen.
124
Dark field microscope
Cells viewed through this microscope stand out as bright objects against a dark background.
125
Electron Microscopes
An electron microscope uses electromagnetic lenses, electrons and a fluorescent screen to produce the magnified image.
The image can be photographed, creating a picture called an electron photomicrograph.
126
Electron Photomicrograph
Image made from electron microscope.
127
Scanning probe microscopes
Use physical probe to produce detailed images of surfaces.
128
Simple staining
If only a single dye is used to stain a specimen, the procedure is called simple staining.
Is a staining technique that uses a basic dye to add color to cells
129
What charge does a basic dye hold?
A basic dye carries a positive charge.
130
Why do basic dyes stains cells?
Basic dyes stain cells because the positively charged dye particles are attracted to the many negatively charged cellular components.
131
Example of basic dyes:
Methylene blue
Crystal violet
Safranin
Malachite green
132
Acidic dyes
- do not stain cells
-can be used for negative staining
133
Negative staining
A procedure that colors the background
134
How does negative staining work?
The cells repel the negatively charged dye, allowing the colorless cell to stand out against the background.
135
An advantage of negative staining
Is that it can be done as a wet mount.
136
Differential staining
Is used to distinguish different groups of bacteria
137
Two most frequently used differential staining techniques
1. Gram stain
2. Acid fast stain
138
Gram stain
Staining technique that divides bacteria into one of two groups, gram positive or gram negative, on the basis of color after staining.
139
Acid fast stain
Is a procedure used to detect a small group of organisms that do not readily take up dyes.
140
Example of a type of bacteria that does not readily take up dyes
Members of the genus mycobacterium
141
Why are mycobacteria difficult to stain and require harsh methods to stain?
The cell wall of these bacteria contain high concentrations of mycolic acids- waxy long chain fatty acids that prevent uptake of dyes such as those used in gram staining.
142
Primary stain
First dye applied in a multi step differential staining procedure; generally stains all cells.
143
Counterstain
In a differential staining procedure, the stain applied to give a contrasting color to the bacteria that do not retain the primary stain.
