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Microbiology: lecture > 04: A Survey of Prokaryotic Cells and Microorgranisms > Flashcards

04: A Survey of Prokaryotic Cells and Microorgranisms Flashcards

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Biology 101 flashcards
1
Q

Characteristics of Cell Life

A
  • Basic shape – spherical, cubical, cylindrical
  • Internal content – cytoplasm, surrounded by a membrane
  • DNA chromosome(s), ribosomes, metabolic capabilities
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2
Q

Eukaryotic cells

A
  • animals, plants, fungi, and protists
  • Contain membrane-bound organelles that compartmentalize the cytoplasm and perform specific functions
  • Contain double-membrane bound nucleus with DNA chromosomes
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3
Q

Prokaryotic cells

A
  • bacteria and archaea
  • No nucleus or other membrane-bound organelles
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4
Q

Characteristics of Life

A
  • Reproduction and heredity
  • Growth and development
  • Metabolism
  • Movement and/or irritability
  • Cell support, protection, and storage mechanisms
  • Transport of nutrients and waste
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5
Q

Structure of a Bacterial Cell

A
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6
Q

External Structures

A
  • Appendages
  1. Motility – flagella and axial filaments (periplasmic flagella)
  2. Attachment or channels – fimbriae and pili
  • Glycocalyx – surface coating
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7
Q

Flagellar Arrangements

A
  • Monotrichous – single flagellum at one end
  • Lophotrichous – small bunches emerging from the same site
  • Amphitrichous – flagella at both ends of cell
  • Peritrichous – flagella dispersed over surface of cell
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8
Q

Flagellar Responses

A
  • Guide bacteria in a direction in response to external stimulus:
  1. Chemical stimuli – chemotaxis; positive and negative
  2. Light stimuli – phototaxis
  • Signal sets flagella into motion clockwise or counterclockwise:
  1. Counterclockwise – results in smooth linear direction – run
  2. Clockwise – tumbles
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9
Q

Which of the following best describes the action of the prokaryotic flagellum?

A. It whips back and forth to move the cell

B. It extends and contracts to move the cell

C. It rotates to move the cell

D. It attaches to the environment and pulls the cell

E. It is capable of all of the above

A

E. It is capable of all of the above

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10
Q

Fimbriae

A
  • Fine, proteinaceous, hairlike bristles emerging from the cell surface
  • Function in adhesion to other cells and surfaces
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11
Q

Pili

A
  • Rigid tubular structure made of pilin protein
  • Found only in gram-negative cells
  • Function to join bacterial cells for partial DNA transfer called conjugation
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12
Q

Glycocalyx

A
  • Coating of molecules external to the cell wall, made of sugars and/or proteins
  • Two types:
    1. Slime layer - loosely organized and attached
    2. Capsule - highly organized, tightly attached
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13
Q

Functions of Glycocalyx

A
  • Protect cells from dehydration and nutrient loss
  • Inhibit killing by white blood cells by phagocytosis, contributing to pathogenicity
  • Attachment - formation of biofilms
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14
Q

Cell Envelope

A
  • External covering outside the cytoplasm
  • Composed of two basic layers:
    1. Cell wall
    2. cell membrane
  • Maintains cell integrity
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15
Q

Gram-Positive Bacteria

A

thick cell wall composed primarily of peptidoglycan and cell membrane

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16
Q

Gram-Negative Bacteria

A

outer cell membrane, thin peptidoglycan layer, and cell membrane

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17
Q

Gram-Positive Cell Wall

A
  • 20 to 80 nm thick peptidoglycan
  • teichoic acid and lipoteichoic acid:
    • function in cell wall maintenance and enlargement during cell division
    • move cations across the cell envelope
    • stimulate a specific immune response
  • Some cells have a periplasmic space between the cell membrane and cell wall
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18
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
  • May function as receptors and blocking immune response
  • Contain porin proteins in upper layer – regulate molecules entering and leaving cell
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19
Q

Gram-Positive Cell Wall

vs

Gram-Negative Cell Wall

A
20
Q

Which of the following is NOT found in the Gram-Negative cell wall structure?

A. Porins

B. Teichoic Acids

C. Periplasmic Space

D. Lipopolysaccharides

E. Peptidoglycan

A

B. Teichoic Acids

21
Q

Gram Stain

A
  • Differential stain that distinguishes cells with a gram-positive cell wall from those with a gram-negative cell wall
    • Gram-positive - retain crystal violet and stain purple
    • Gram-negative - lose crystal violet and stain red from safranin counterstain
  • Important basis of bacterial classification and identification
  • Practical aid in diagnosing infection and guiding drug treatment
22
Q

Nontypical Cell Walls

A
  • Mycobacterium and Nocardia
    • 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 caused by these microorganisms
  • Some have no cell wall
    • Mycoplasma
    • Cell wall is stabilized by sterols
    • Pleomorphic
23
Q

Nucleoid

A
  • Chromosome
    • Single, circular, double-stranded DNA molecule that contains all the genetic information required by a cell
  • Plasmids
    • 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
24
Q

Endospores

A
  • Inert, resting, cells produced by some G+ genera:
    • Clostridium
    • Bacillus
    • Sporosarcina
  • Have a 2-phase life cycle:
    1. Vegetative cell – metabolically active and growing
    2. Endospore – when exposed to adverse environmental conditions; capable of high resistance and very long-term survival
25
Q

Sporulation

A
  • formation of endospores
    • Hardiest of all life forms
    • Withstands extremes in heat, drying, freezing, radiation, and chemicals
    • Not a means of reproduction
26
Q

Germination

A

return to vegetative growth

27
Q

Endospores

A
  • Dehydrated, metabolically inactive
  • Thick coat
  • Longevity verges on immortality, 250 million years
  • Resistant to ordinary cleaning methods and boiling
  • Pressurized steam at 120°C for 20-30 minutes will destroy
28
Q

If you discover that the bacterium you’re studying stores phosphate, which of the following would you expect to contain the stored phosphate?

A. Granules

B. Ribosomes

C. Plasmids

D. Lipopolysaccharides

E. Endospores

A

A. Granules

29
Q

Bacterial Shapes

A
  1. Coccus – spherical
  2. Bacillus – rod
  3. Spirillum – helical, comma, twisted rod
30
Q

Coccus

A

Spherical

31
Q

Bacillus

A

Rod

  • Coccobacillus – very short and plump
  • Vibrio – gently curved
32
Q

Spirillum

A

Helical, comma, twisted rod

  • Spirochete – spring-like
33
Q

Bacterial Arrangements

A

Arrangement of cells is dependent on pattern of division and how cells remain attached after division

34
Q

Bacterial Arrangements: Cocci

A
  1. Singles
  2. Diplococci – in pairs
  3. Tetrads – groups of four
  4. Irregular clusters
  5. Chains
  6. Cubical packets (sarcina)
35
Q

Bacterial Arrangements: Bacilli

A
  1. Diplobacilli
  2. Chains
  3. Palisades
36
Q

Major Taxonomy Groups of Prokaryotes

A
  • Domain Archaea:
    • primitive
    • adapted to extreme habitats
    • modes of nutrition
  • Domain Bacteria:
    • Phylum Proteobacteria – Gram-negative cell walls
    • Phylum Firmicutes – mainly Gram-positive with low G + C content
    • Phylum Actinobacteria – Gram-positive with high G + C content
37
Q

Cocci in clusters or packets that are aerobic or facultative

A

Family Staphylococcaceae:

Staphylococcus (members cause boils, skin infections)

38
Q

Cocci in pairs and chains that are facultative

A

Family Streptococcaceae:

  • Streptococcus (species cause strep throat, dental caries)
39
Q

Anaerobic cocci in pairs, tetrads, irregular clusters

A

Family Peptococcaceae:

  • Peptococcus
  • Peptostreptococcus (involved in wound infections)
40
Q

Spore-forming rods

A

Family Bacillaceae:

  • Bacillus (anthrax)
  • Clostridium (tetanus, gas gangrene, botulism)
41
Q

Non-sporeforming rods

A

Family Lactobacillaceae:

  • Lactobacillus
  • Listeria (food infection)
  • Erysipelothrix (erysipeloid)
42
Q

Round bacterial cells growing in irregular clusters would be best described as:

A. Streptococci

B. Streptobacilli

C. Staphylococci

D. Tetrads

A

C. Staphylococci

43
Q

Prokaryotes with Unusual Characteristic

A
  • Free-living nonpathogenic bacteria
  • Photosynthetic bacteria – use photosynthesis, can synthesize required nutrients from inorganic compounds
    • Cyanobacteria (blue-green algae)
    • Green and purple sulfur bacteria
    • Gliding, fruiting bacteria
44
Q

Cyanobacteria

A
  • Gram-negative cell walls
  • Extensive thylakoids with photosynthetic chlorophyll pigments and gas inclusions
45
Q

Green and Purple Sulfur Bacteria

A
  • Photosynthetic
  • Contain photosynthetic pigment bacteriochlorophyll
  • Do not give off oxygen as a product of photosynthesis
46
Q

Archaea

A
  • Live in the most extreme habitats in nature, extremophiles
  • Adapted to heat, salt, acid pH, pressure, and atmosphere
    • methane producers
    • hyperthermophiles
    • extreme halophiles
    • sulfur reducers
47
Q

Organisms in the Domain Archaea have peptidoglycan in their cell wall.

A. True

B. False

A

B. False

Microbiology: lecture (8 decks)

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