Chapter 2: part 2 Flashcards
1
Q
Gram-positive Cell Wall
A
- measured in nanometers
- thick peptidoglycan
- includes teichoic acid and lipoteichoic acid
-some cells have a periplasmic space, between the cell membrane and cell wall
2
Q
Gram-positive Cell Wall Characteristics
A
- Major Layers: one
- Chemical composition: Teichoic acid, Peptidoglycan (thick), Lipoteichoic acid
- Thick (20-80nm)
- No outer membrane
- Narrow periplasmic space
- Permeability to molecules: more penetrable
3
Q
Gram-negative Cell Wall
A
- Inner and outer membranes and periplasmic space between them contains a thin peptidoglycan layer
- Outer membrane contains lipopolysaccharides (LPS) (lipid portion endotoxin) may become toxic when released during infections
- Contain Porin proteins in upper layer- regulate molecules entering and leaving the cell
4
Q
Gram-negative Cell Wall Characteristics
A
- Major Layers: two
- Chemical composition: Lipopolysaccharides (LPS), Porin proteins
- Thin (8-11nm)
- Outer membrane
- Extensive periplasmic space
- Permeability to molecules: less penetrable
5
Q
The Gram Stain
A
Differential stain that distinguishes cells with gram-positive cell wall from those with gram-negative cell wall
- Gram-positive: retain crystal violet and stain purple
- Gram-negative: loose crystal violet and stain red from safranin counterstain
- Important basis of bacterial classification and identification
- Practical aid in diagnosing infection and guiding drug treatment
6
Q
In the Gram Stain, what does the Gram-positive do?
A
retain crystal violet and stain purple
7
Q
In the Gram Stain, what does the Gram-negative do?
A
looses crystal violet and stain red from safranin counterstain
8
Q
Endotoxins
A
- Gram-negative
- Contained in
- General effect
- General physiological effects: fever, malaise, aches, shock
- Toxic in higher doses (need more to get sick)
- Ex of diseases: Meningitis, endotoxic shock, salmonellosis
9
Q
Exotoxins
A
- Gram-positive
- Secreted out
- Specific effects
- Target organs are damaged; heart muscles, blood cells, intestinal tract show disfunctions
- Ex of diseases: tetanus, diphtheria, cholera, anthrax
10
Q
Gram Stain Procedure
A
- Application of crystal violet (purple dye)
- Application of iodine (mordant)
- Alcohol wash (decolorization)
- Application of Safranin (counterstain)
- crystal violet is the primary stain because its first
- positive always retains the first color
11
Q
Atypical (Nontypical) Cell Walls
A
- some bacterial groups lack typical cell wall structure, i.e. Mycobacterium
- some have no cell wall, i.e. Mycoplasma
12
Q
Atypical (Nontypical) Cell Walls: Mycobacterium
A
- lack typical cell wall structure
- Gram-positive cell wall structure with lipid mycolic acid (cord factor)
- Pathogenicity and high degree of resistance to certain chemicals and dyes
- Basis for acid-fast stain used for diagnosis of infections cause by these microorganisms
13
Q
Atypical (nontypical) Cell Walls: Mycoplasma
A
- have no cell wall
- Pleomorphic (no cell wall to give it shape)
- Membrane is stabilized by sterols (absorbed from the media-limiting factor; does not make sterols so it it takes from whatever media its in)
14
Q
Cell Membrane Structure
A
-Phospholipid bilayer with embedded proteins- fluid mosaic model
Function in:
-site for energy reactions, nutrient processing, and synthesis
-passage of nutrients into the cell and discharge of wastes
-selectively permeable
15
Q
Cell Membrane Structure Functions In:
A
- site for energy reactions, nutrient processing, and synthesis
- passage of nutrients into the cell and discharge of wastes
- selectively permeable
16
Q
Cytoplasm
A
- Dense gelatinous solution of sugars, amino acids, and salts
- 70-80% water
- serves as solvent for materials used in all cell functions
17
Q
Nucleoid Region: Chromosome
A
- single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell
- part of cell membrane
18
Q
Nucleoid Region: Plasmids
A
(extra chromosomal piece of DNA)
- Free small circular, double-stranded DNA
- Not essential to bacterial growth and metabolism
- Used in genetic engineering
- Readily manipulated and transferred from cell to cell
19
Q
Prokaryotic Ribosomes
A
- Made of 60% ribosomal RNA and 40% protein
- Consists of 2 subunits:
1. Large (50S) and
2. Small (30S) =Ribosome (70S) - Differ from Eukaryotic ribosomes in size and number of proteins
- site of protein synthesis
- found in all cells
- (Svedberg)- ribosomes characterized by molecular size of components using ultracentrifuge
20
Q
Svedberg (S)
A
Ribosomes characterized by molecular size of components using ultracentrifuge
21
Q
Inclusions
A
-Reserve Deposits (intracellular storage bodies can be used when environmental supplies depleted)
-Vary in size, number, content
-Non-living, crystal-like, permanent or temporary
-May be diagnostic (used for ID) e.g. “Negri bodies” (black inclusions only present if rabies virus is there
Ex: Magnetosomes: crystalline particles of iron oxide function in navigation in water
22
Q
Cytoskeleton
A
Many bacteria possess an internal network of protein polymers that is closely associated with the cell wall
23
Q
Endospores
A
- Inert (not active), resting, cells produced by some Gram-Positive genera: Clostridium, Bacillus, Sporosarcina
- Have a 2 phase life cycle:
1. Vegetative Cell- metabolically active and growing
2. Endospore- formed when exposed to adverse environmental conditions (STRESS); capable of high resistance (PROTECTED) and very long-term survival (RESISTANT TO NORMAL CONTROL METHODS)
24
Q
Endospore 2 Phase Life Cycle
A
- Vegetative Cell- metabolically active and growing
- Endospore- formed when exposed to adverse environmental conditions (STRESS); capable of high resistance (PROTECTED) and very long-term survival (RESISTANT TO NORMAL CONTROL METHODS)
25
Sporulation (sporogenesis)
formation of endospores
- hardiest of all life forms
- withstands extremes in heat (boiling). freezing, radiation, and chemicals
- not a means of reproduction
26
Germination
return to vegetative growth
27
Endospores continued...
- Dehydrated, metabolically inactive
- Thick spore coat
- Longevity verges on immortality, 250 million years
- Position in vegetative cell is genetically programmed
- Elimination: pressurized steam at 120 Degrees Celsius for 20-30 minutes will destroy (autoclave)
28
How to Destroy Endospores
pressurized steam at 120 degrees Celsius for 20-30 minutes will destroy (autoclave)
29
Biofilm
Ex: Dental plaque on tooth surface
Formation:
-organic surface-- cell sticks to coating-- as cells divide they form a dense mat bound together by sticky extracellular deposits-- additional microbes are attracted to developing film and create a mature community with complex function
30
Classification Criteria for Prokaryotes
Phenotypical: (can see)
- Microscopic morphology- shape, arrangement, staining
- Macroscopic morphology- colony appearance
- Bacterial physiology- chemical reactions
- Serological analysis
Genotypic:
-genetic and molecular analysis
31
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Bacterial Taxonomy (based on bergey's manual):
Bergey's Manual Of Determinative Bacteriology
```
-five volume resource covering all known prokaryotes; 1923-1994
-based on PHENOTYPIC characteristics
-volumes determined by cell wall composition
Medical use (diagnostic):
-Restricted to bacterial disease agents
-Divides bacteria based on cell wall structure, shape, arrangement, and physiological traits
32
Bacterial Taxonomy (based on bergey's manual): Bergey's Manual of Systematic Bacteriology
- five volume resource; 1st ed. 1984-1989; 2nd ed. 2001-2002
- based on GENOTYPIC (rRNA) characteristics
- phylogenic system (evolutionary relationships)
33
Major Taxonomic Groups of Prokaryotes
- Domain Archaea- primitive, adapted to extreme habitats and modes of nutrition
- Domain Bacteria:
- Phylum Proteobacteria: Gram-negative cell walls (Rickettsias, Enterics, Vibrios)
- Phylum Firmicutes: Gram-positive with low G + C content (Bacillus, Clostridium, Staphylococcus, Streptococcus)
- Phylum Actinobacteria: Gram-positive with high G + C content (Corynebacterium, Mycobacterium, Micrococcus, Streptomyces)
- Phylum Chlamydiae (Chlamydia, Chlamydophila)
- Phylum Spirochaete (Treponema, Borrelia, Leptospira)
34
Major Taxonomic Groups of Prokaryotes: Domain Archaea
primitive, adapted to extreme habitats and modes of nutrition
35
Major Taxonomic Groups of Prokaryotes: Domain Bacteria
- Phylum Proteobacteria- Gram-negative cell walls (Rickettsias, Enterics, Vibrios)
- Phylum Firmicutes- main Gram-positive with low G + C content (Bacillus, Clostridium, Staphylococcus, Streptococcus)
- Phylum Actinobacteria- Gram-positive with high G + C content (Corynebacterium, Mycobacterium Micrococcus, Streptomyces)
- Phylum Chlamydiae (Chlamydia, Chlamydophila)
- Phylum Spirochaete (Treponema, Borrelia, Leptospira)
36
Unusual Forms of Medically Significant Bacteria: Rickettsias
- very tiny, gram-negative bacteria
- rod-shaped
- most are pathogens
- obligate intracellular pathogens
- transmitted by arthropod vectors
- Family- Rickettsiaceae
- Rickettsia rickettsii- rocky mountain spotted fever (tick)
- Rickettsia prowazekii- epidemic typhus (louse)
37
Unusual Forms of Medically Significant Bacteria: Chlamydias
- tiny
- coccoid (spherical)
- obligate intracellular parasites
- transmitted by air or contact (including sexual)
- Family Chlamydiaceae (2 genera)
- Chlamydia trachomatis-m can cause urogenital infections, trachoma, conjunctivitis, pneumonia and lymphogranuloma venereum (LGV)
- Chlamydia pneumoniae- can cause bronchitis, sinusitis, pneumonia and possibly atherosclerosis
- Chlamydia psittaci- can cause pneumonia (psittacosis)
38
Types of Chlamydias
- Chlamydia Trachomatis- cause urogenital infections, Trachoma, conjunctivitis, pneumonia and lymphogranuloma venereum (LGV)
- Chlamydia pneumoniae- cause bronchitis, sinusitis, pneumonia and possibly atherosclerosis
- Chlamydophila psittaci- cause pneumonia (psittacosis)
39
Archaea: The other Prokaryotes
- constitute third domain archaea
- more closely related to eukarya than to bacteria
- contain unique genetic sequences in their rRNA
- have unique membrane lipids and cell walls
40
Archaea
- live in the most extreme habitats in nature, extremophiles
- adapted to heat, salt. acid pH, pressure, and atmosphere:
- Acidophiles
- Halophiles (salt)
- Thermophiles
- Includes: methane producers, hyperthermophiles, extreme halophiles and sulfur reducers
