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Microbiology > Introduction To Bacteriology > Flashcards

Introduction To Bacteriology Flashcards

Bacteria

1
Q

What is a prokaryote?

A

A prokaryote is a cellular organism that lacks an envelope-enclosed nucleus.

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2
Q

What are eukaryotes?

A

Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

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3
Q

What are the examples of prokaryote?

A

Bacteria and archaea

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4
Q

Examples of eukaryotes

A 
Algae
Fungi
Protozoa
Plants
Animals
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5
Q

Approximate size of prokaryote

A

0.5 - 3.0 micrometres

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6
Q

Approximate size of eukaryotes

A

More than 5.0 micrometers

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7
Q

Describe the nuclear structures in terms of nucleus and chromosomes of prokaryote and eukaryotes

A

Nucleus:
Pro- no nuclear membrane
Eu- nuclear membrane present

Chromosomes:
Pro- single, circular DNA haploid genome
Eu- strands of DNA diploid genome

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8
Q

What are the cytoplasmic structure absent in prokaryotes but present in eukaryotes?

A

Mitochondria
Golgi bodies
Endoplasmic reticulum

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9
Q

Number of ribosome for prokaryote and eukaryotes

A

Pro - 70S ( 50S + 30S)

Eu - 80S ( 60S + 40S)

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10
Q

Difference between prokaryote and eukaryotes in terms of cytoplasmic membrane

A

For prokaryote, cytoplasmic membrane does not contain sterols whereas eukaryotes have sterols

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11
Q

Cell wall for prokaryote n eukaryotes

A

Pro - have complex structures

Eu- present for fungi, otherwise absent

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12
Q

Reproduction for prokaryote n eukaryotes

A

Pro - asexual ( binary fission)

Eu - sexual n asexual

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13
Q

Respiration for prokaryote n eukaryotes

A

Pro- via cytoplasmic membrane

Eu - via mitochondria

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14
Q

Movement for prokaryote n eukaryotes

A

Pro- simple flagellum if present

Eu- complex flagellum if present

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15
Q

What are the two components of outer layer of bacterial cell?

A

Rigid cell wall

Cytoplasmic membrane- present beneath cell wall

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16
Q

Components of cytoplasm of bacterial cell

A

Cytoplasmic inclusions
Ribosome
Mesosomes
Genetic material

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17
Q

Additional structures of bacterial cell

A

Capsule
Flagella
Fimbriae (pili)
Spores

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18
Q

Bacterial components can be classified into two. What are they? Examples

A 
Essential components :
Ribosomes
Nucleoid DNA 
Cell wall
Cell/ Plasma membrane
Mesosomes
Periplasm
Nonessential components:
Glycocalyx
Granule
Capsule
Plasmid
Flagella
Pilus/fimbriae
Spore
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19
Q

What is mesosome?

A

It is an organelle of bacteria that appears as an invagination of the plasma membrane

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20
Q

Description of glycocalyx

A
  • substances that surround cells
  • viscous,gelatinous polymer, composed of polysaccharide and/or polypeptide
  • if organized and firmly attached to the cell wall = capsule
  • if unorganized and loosely attached to the cell wall = slime layer
  • important component of biofilm(helps cell to attach to various surfaces and to each other)
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21
Q

What is virulence in bacteria

A

Virulence is described as an ability of an organism to infect the host and cause a disease.

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22
Q

Functions of glycocalyx in bacteria

A
  • contribute to bacterial virulence
  • protect bacteria from phagocytosis by the cell of the host
  • protect against dehydration
  • inhibit movement of nutrient out of the cell
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23
Q

Examples of bacteria virulence with the help of glycocalyx

A
  • encapsulated Bacillus anthracis causes anthrax

- capsulated Streptococcus pneumoniae causes pneumonia

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24
Q

Description of flagella

A

-long filamentous appendages

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25
Q

What is atrichous

A

Lack of flagella

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26
Q

Types of flagella

A

Peritrichous

Polar:

  • monotrichous
  • lophotrichous
  • amphitrichous
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27
Q

Function of flagella

A

For movement of a bacteria (motility)

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28
Q

Peritrichous description and its example species

A
  • distributed over entire cell

- escherichia coli

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29
Q

Monotrichous and polar

Description and its example

A
  • a single flagellum at one poles or ends of the cell

- vibrio cholerae

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30
Q

Lophotrichous and polar

Description and example

A
  • a tuft of flagella coming from one pole

- helicobacter pylori

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31
Q

Amphitrichous and polar

Description and example

A
  • at both pole of the cell

- Campylobacter jejuni

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32
Q

Pili or fimbriae description

A

-hairlike appendages - shorter, straighter, thinner than flagella

Fimbriae:

  • occur at the poles or evenly distrusted over the entire surface of the cell
  • a few to several hundred per cell

Pili:

  • longer than fimbriae
  • one or two per cell
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33
Q

Function of pili or fimbriae

A

Fimbriae:
Mediate attachment to each other and to surfaces (liquids, glass and rocks) or epithelial surfaces in the body

Pili:

  • for attachment
  • for DNA transfer (sex pilus mediate attachment of two bacteria during conjugation)
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34
Q

Description of cell wall of bacteria

A
  • complex and semi-rigid structure
  • determine the shape of the bacteria
  • to differentiate types of bacteria
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35
Q

Functions of cell wall of bacteria

A

-prevent bacterial cells from bursting
-clinically;
~contribute to the ability of some species to cause disease
~the site of action of some antibiotics

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36
Q

Description of cell membrane of bacteria

A
  • contains phospholipids

- enclosing the cytoplasm

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37
Q

Functions of cell membrane of bacteria

A
  • semipermiable barrier (selectively) - materials enter and exit the cell
  • energy generation
  • synthesis of precursors of cell wall
  • secretion of enzymes and toxins
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38
Q

Descriptions of cytoplasm of bacteria

A
  • contains 80% water and primarily protein, carbohydrates, lipids, inorganic ions and low molecular weight compounds
  • major structures are a nucleoid, ribosomes and inclusions(granules)
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39
Q

Description of nucleoid of bacteria

A
  • a region in cytoplasm where the chromosomal DNA is located
  • a single, continuous, circular double-stranded DNA
  • contains genetic information
  • it contains all the information needed to make protein
40
Q

Function of nucleoid of bacteria

A

Replication of DNA

41
Q

What is DNA replication?

A

DNA replication is the process by which DNA makes a copy of itself during cell division

42
Q

Description of plasmid of bacteria

A
  • small, circular, supercoiled, double-stranded DNA
  • extrachromosomal genetic element, not connected to bacterial chromosome
  • replicate independently
  • can be transferred to other bacterium
43
Q

Functions of plasmid of bacteria

A

Carry genes for ;

  • antibiotic resistance
  • tolerance to toxic metals
  • production of toxins
  • synthesis of enzymes
44
Q

Description and function of ribosome

A

Description:
Composed of a large and a small subunit

Function:
Involve in protein synthesis

45
Q

Description of inclusions and its examples

A

Description:
Reserve deposits

Examples:

  • metachromatic granules
  • polysaccharide granules
  • lipid inclusions
  • sulfur granules
46
Q

Function of inclusions of bacteria

A

Accumulate certain nutrients when they are plentiful and use them when the environment is deficient.

47
Q

Endospore known as

A

‘resting’ cell

48
Q

When does endospore forms

A

Forms when essential nutrients are depleted

49
Q

Features of endospore

A
  • resistant to heat, toxic chemicals and radiation
  • survive for many years (remain dormant)
    Dormant=inactive
  • no metabolic activity ( antibiotics are ineffective)
50
Q

What is the name of the process of endospore formation?

A

Sporulation or sporogenesis

51
Q

What is the sporm-forming genera?

A

Clostridium

Bacillus

52
Q

What are the location of endospore formation? And each examples species

A

Terminal - Clostridium tetani
Subterminal - Clostridium perfringens
Central - Bacillus spp.

53
Q

What is the another name of spore staining?

What is the use?

A
  • Schaeffer-Fulton

- it is used to see spores of bacteria

54
Q

Steps in the formation of endospore

A
  1. DNA is replicated
  2. DNA aligns along the cell’s long axis
  3. Cytoplasmic membrane invaginates to form forespore
  4. Cytoplasmic membrane grows and engulfs forespore within a second membrane. Vegetative cell’s DNA disintegrates.
  5. A cortex of calcium and dipicolinic acid is deposited between the membrane.
  6. Spore coat forms around endospore.
  7. Maturation of endospore; completion of spore coat and increase in resistance to heat and chemicals by unknown process.
  8. Endospore released from original cell.
55
Q

Size of bacterial cells

A
  • 0.2 to 2.0 micrometer in diameter

- 2 to 8 micrometer in length

56
Q

Shape of bacterial cells and its arrangements

A

Coccus - diplococci, streptococci, tetrad, sarcinae, staphylococci

Bacillus/rod - single bacilli, diplobacilli, streptobacilli, coccobacilli

Spiral - vibrio (curved rod), spirillum (helical), spirochete ( helical and flexible)

57
Q

Bacterial cell wall composed of what?

It is known as what?

A

Composed of peptidoglycan

Known as murein

58
Q

What is peptidoglycan?

A

Peptidoglycan consists of a repeating disaccharide attached by polypeptide.

59
Q

Describe the disaccharide in the peptidoglycan?

A

Disaccharide is made up of monosaccharide called N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which is related to glucose.

60
Q

How does carbohydrate ‘backbone’ is formed?

A

Alternating N-acetylmuramic acid (NAM) and N-acetylglucosamine acid(NAG) molecules are linked in rows of 10 to 65 sugars to form a carbohydrate’backbone’.

61
Q

Describe gram-positive cell walls

A
  • consists thick layers of peptidoglycan - forms a thick, rigid structure
  • permeable to many substances ( sugars and amino acids)
  • a prominent component = teichoic acids
62
Q

Description of teichoic acid in cell wall of gram-positive bacteria

A
  • a chains of common subunit: ribitol-phosphate or glycerol-phosphate ( various sugars and D-alanine are usually attached)
  • joined to peptidoglycan through covalent bonds
63
Q

Two classes of teichoic acids? Description of each class

A

a) lipoteichoic acid - which spans the peptidoglycan layer and is linked to the plasma membrane
b) wall teichoic acid - which is linked to the peptidoglycan layer

64
Q

Functions of the teichoic acid

A
  • teichoic acid (negative charge) bind and regulate the movement of cations (positive ions) into and out of the cell.
  • prevent extensive wall breakdown and cell lysis
  • provide antigenic specificity (for identification of gram-positive bacteria)
65
Q

Description of gram-negative cell walls

A
  • consists of thin (one or a few) layers of peptidoglycan and an outer membrane (lipid bilayer embedded with proteins)
  • the peptidoglycan is bonded to lipoprotein in the outer membrane and is in the periplasm
  • do not contain teichoic acids
66
Q

Disadvantage of thin layer of peptidoglycan in gram-negative cell walls

A

More susceptible to mechanical breakage

67
Q

Periplasm in gram-negative cell wall description

A
  • a gel-like fluid

- it contains a high concentration of degradative enzymes and transport proteins

68
Q

Description of outer membrane of gram-negative bacteria

A
  • consists of lipopolysaccharide (LPS), lipoprotein and phospholipids
  • strong negatively charge - important factor in evading phagocytosis and the actions of implement
  • provide a barrier to certain antibiotics, digestive enzymes such as lysozyme, detergents, heavy metals , bile salts and certain dyes.
  • permeability of the outer membrane is due to porins (specialized channel-forming proteins)
69
Q

Function of porins (specialized channel-forming proteins) in outer membrane of gram-negative

A

Permits passage of molecules such as nucleotides, disaccharides, peptides, amino acids, vitamin B12 and iron

70
Q

What is lipopolysaccharide (LPS) molecule?

A

Is a large complex molecule contains lipids and carbohydrates

71
Q

What are the three components of lipopolysaccharide?

A
  • lipid A
  • core polysaccharide
  • O polysaccharide
72
Q

Description of lipid A in lipopolysaccharide

A
  • the lipid portion of the LPS and is embedded in the top layer of the outer membrane
  • release when bacteria die - functions as endotoxin
  • responsible for the symptoms associated with infections (fever, dilation of blood vessels, shock and blood clotting)
73
Q

Function of lipid A

A

Endotoxin

74
Q

Description and function of core polysaccharide

A

Description - attached to lipid A

Function - to provide stability

75
Q

Description and function of O polysaccharide (medical significance)

A

Description - extend outwards from the core polysaccharide and is composed of sugar molecules

Function

  • as an antigen
  • useful for distinguishing species of gram-negative bacteria
76
Q

Difference between gram-positive and gram-negative bacterial cell wall

A

Component. Gram-positive. Gram-negative
Peptidoglycan. . Thick layer. Thin layer
Teichoic acid. Present. Absent
Outer membrane. . Absent. Present
Lipopolysaccharide. Absent. Present
Porin proteins. Absent. Present
Periplasm. Absent. Present

77
Q

Why we should stain bacteria?

A

Bacteria have nearly the same refractive index as water, therefore, when they are observed under a microscope, they are opaque or nearly invisible to the naked eye.

78
Q

What is a stain?

A

A stain is a substance that adheres to a cell, giving the cell colour.

79
Q

Use of stain

A
  • to differentiate different types of organisms

- to view specific parts of organisms

80
Q

Types of stain based on their functions. Description and examples

A
  1. Simple staining - only one dye is used
    • differentiation among bacteria is impossible
      Example - simple staining
  2. Differential staining - more than one dye is used
    • differentiation among bacteria is impossible
      Example - Gram’s staining , Acid-fast staining
  3. Special staining - more than one dye is used
    • special structures are seen
      Example - Capsule staining , Spore staining
81
Q

Purpose of gram-staining

Stain colour for both bacteria?

A

To differentiate between two groups of bacteria

Gram-positive cells : purple-staining
Gram-negative cells : pink-staining

82
Q

What are the reagents used in the gram-staining?

A

Crystal violet
Lugol’s iodine
Acetone-iodine
Safranin

83
Q

Steps of gram staining

A
  1. Slide is flooded with crystal violet for 1 min, then rinsed with water.
  2. Slide is flooded with Lugol’s iodine for 1 min, then rinsed with water.
  3. Slide is flooded with acetone-iodine for 10 sec, then rinsed with water.
  4. Slide is flooded with safranin for 30 sec, then rinsed with water and blotted dry.
84
Q

Step 1 : slide is flooded with crystal violet for 1 min, then rinsed with water

What is the observation/ result and inference?

A

Result : all cells are stained purple

Inference: the dye enters the cytoplasm of both types of cells

85
Q

Step 2: slide is flooded with Lugol’s iodine for 1 min, then rinsed with water

What is the observation/ result and inference?

A

Result: iodine acts as a mordant; all cells remain purple

Inference: iodine forms large crystals with the dye that are too large to escape through the cell wall (decreasing solubility of the dye)

86
Q

Step 3 : slide is flooded with acetone-iodine for 10 sec, then rinsed with water

What is the observation/ result and inference?

A

Result : smear is decolorized; gram-positive cells remain purple, but gram-negative cells are now colourless

Inference:
alcohol dehydrates the peptidoglycan of gram-positive cells to make it more impermeable to the crystal violet-iodine.

Alcohol dissolves the outer membrane of gram-negative cells and leaves small holes in the peptidoglycan layer through which crystal violet-iodine diffuse.

87
Q

Step 4 : slide is flooded with safranin for 30 sec, then rinsed with water and blotted dry.

What is the observation/ result and inference?

A

Result: gram-positive cells remain purple, gram-negative cells are pink

Inference:
because gram-negative bacteria are colourless, the addition of safranin turns the cells pink.

Gram-positive bacteria absorbed the safranin, but it is masked by darked purple dye

88
Q

Acid fast stain used for what organism? Why?

A

Mycobacterium structure
This is because it contains large amount of fatty waxes (mycolic acid) within their cell wall.
This resist staining by ordinary methods.
Requires a special stain for diagnostic called acid fast stain.

89
Q

Describe the principle of acid fast staining procedures

A

Mycobacteria contain a high amount of fatty waxes called mycolic acid.
They can be stained by hot carbol-fuchsin, but they resist decolorization with acid-alcohol, so they remain red.
All other cells are stained blue by the counter stain (methylene blue)

90
Q

Acid-fast stain basic requirements

A
  1. Primary and mordant staining with strong carbol-fuchsin (red)
  2. Decolorization with acid alcohol : the acid alcohol contains 3% HCL and 95% ethanol or 20% H2SO4
  3. counterstain with methylene blue
91
Q

Result of acid fast stain

A

Acid-fast cells - red

Non Acid-fast cells - blue

92
Q

What are the reagents used in Acid-fast stain and their functions

A

Carbol fuchsin - primary dye
Acid alcohol - decolorizer
Methylene blue - counter stain

93
Q

Colour changes for non- acid fast cell during Acid-fast stain

A

Red
Colourless
Blue

94
Q

Special stain used for what

A

Used to stain special structures of bacteria.

95
Q

What are the structures of bacteria can be seen through special stain

A

Capsule
Spore
Flagella
Metachromatic granules

96
Q

Bacteria is classified according to four major characteristics. What are they?

A
  1. Shape and arrangement: coccus, bacillus and spiral
  2. Gram stain reaction - gram-positive and gram-negative
  3. Biochemical and growth characteristics
    - aerobic and anaerobic
    - spore formation
    - biochemical profile
  4. Antigenic structure - antigens in cell body, capsule, flagella

Microbiology (6 decks)

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