Microbiology > Chapter 2: part 2 > Flashcards

Chapter 2: part 2 Flashcards

(40 cards)

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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

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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
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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
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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
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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
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6
Q

In the Gram Stain, what does the Gram-positive do?

A

retain crystal violet and stain purple

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7
Q

In the Gram Stain, what does the Gram-negative do?

A

looses crystal violet and stain red from safranin counterstain

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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
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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
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10
Q

Gram Stain Procedure

A
  1. Application of crystal violet (purple dye)
  2. Application of iodine (mordant)
  3. Alcohol wash (decolorization)
  4. Application of Safranin (counterstain)
    - crystal violet is the primary stain because its first
    - positive always retains the first color
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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
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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
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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)
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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

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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
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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
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17
Q

Nucleoid Region: Chromosome

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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

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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

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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)

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A

Ribosomes characterized by molecular size of components using ultracentrifuge

21
Q

Inclusions

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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

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A

Many bacteria possess an internal network of protein polymers that is closely associated with the cell wall

23
Q

Endospores

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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

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A
  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)
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
``` 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
Microbiology
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