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Bugs and Drugs > Bacteriology > Flashcards

Bacteriology Flashcards

1
Q

What is a spheroplast?

A

Gram neg bacteria that has retained some or all of its outer membrane following:
1. lysozyme hydrolysis or
2. inhibition of cell wall synthesis
by antimicrobial agents.

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2
Q

What type of cell (G+ or G-) would have a porin?

A

Gram negative because a porin is a protein outer membrane channel that

  1. allows the passage of substances through the cell wall
  2. serves as an attachment site for other substances
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3
Q

What is the function of bacterial cell walls?

What gives the cell wall is structure?

A

Cell walls have a high peptidoglycan content which confers rigidity and shape for the cell

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4
Q

What are the two typical functions of a bacterial capsule?

A
  1. anti-phagocytic

2. vaccinogenic

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5
Q

How many chromosomes do bacterial cells have?

Describe the genome structure.

A

1 chromosome (but they can have multiple copies of the same chromosome)

The genome is usually circular and lacks histones

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6
Q

What is the size range of bacteria?

Compare this to the size of a RBC.

A

0.2-2 microns in diameter

RBC- 10 microns

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7
Q

What are the two possible shapes for bacteria?

A

bacilli (rods) and cocci (spheres)

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8
Q

If cocci incompletely divide, they can form three distinct patterns. What are they?
Give an example of each.

A
  1. diplococci- pairs like pneumococci, meningococci or gonococci
  2. chains like streptococci
  3. “grape-like clusters” like stapholycoccus
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9
Q

What are the five general shapes of bacilli? Give an example of each.

A
  1. classic- E. coli
  2. coccobacilli- francisella
  3. Fusiform (tapered ends)- IDK
  4. Helical - treponema pallidum (syphilis)
  5. Hook-shaped- Vibrio cholera
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10
Q

What is the size of the ribosome for bacterial cells?

Why is this important?

A

70S- this is important because it can be a good drug target. The eukaryotic ribosome is 80S, so antimicrobials can be directed specifically at the bacterial cell

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11
Q

Approximately how many genes does a bacterial genome encode?

A

5000 but they also have plasmids

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12
Q

Where is the chromosome found in the bacterial cell? Why?

A

attached to the mesosome (an invagination of the cytoplasmic membrane).
It plays a role in segregation of the daughter chromosomes after replication.

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13
Q

What are the four major storage granules?

A
  1. Glycogen
  2. Poly-beta-hydroxy-butyrate (PBHB)
  3. Sulfur
  4. Metachromatic granules (polymerized metaphosphate)
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14
Q

What are metachromatic granules?
What type of bacteria have them?
How are they stained?

A
  • polymerized metaphosphates (PO3)n
  • corynebacteria diptheria
  • methylene blue
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15
Q

Describe the structure and size of a plasmid.

What two important things can plasmids carry?

A

They are smaller than the chromosome, supercoiled and circular.
They carry:
1. virulence factors
2. antibiotic resistance genes

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16
Q

What are the two medically relevant bacteria that produce spores?
What is the shape and how do they gram stain?
How are they differentiated?

A

Clostridium and Bacillus- both gram+ rods

Clostridium is an obligate anaerobe
Bacillus is an obligate aerobe

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17
Q

What is a spore? What benefit does it confer for the bacteria?

A

It is a dormant cell (not undergoing replication).

It is resistant to physical stress like heat, bactericidal agents and desiccation (drying out)

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18
Q

Spores do not undergo _________ only___________.

When nutritional conditions become favorable they will _________________________.

A

Spores do not undergo division, only germination.

When conditions are favorable, they will germinate to produce a single vegetative cell that can divide further

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19
Q

Why do bacterial cytoplasmic membranes have more proteins than eukaryotic cell membranes?

A

Bacterial cells lack membrane bound organelles (like mitochondria) so their cytoplasmic membrane is where cytochromes and enzymes involved in oxidative phosphorylation reside

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20
Q

What do bacterial cell membranes lack, that eukaryotic cell membranes have?
What is the one bacterial exception?

A

Bacterial cell membranes lack cholesterol/sterols with the exception of mycoplasmas

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21
Q

Describe the process of doing a gram stain.

A
  1. Smear bacteria onto slide and heat fix
  2. Dye with crystal violet or a cationic dye (basic)
  3. Add Iodine to complex the crystal violet to the cell wall
  4. Rinse with ethanol or acetone (Decolorization)
  5. Counterstain with safranin (another basic cationic dye)

At the end of the stain, G+ = purple, G- = pink

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22
Q

After the alcohol step of gram staining, what color will G+ and G- bacteria be?

A 
G+ = purple
G- = colorless
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23
Q

It is not ________ itself, but rather the ______________ that influences the gram stain reaction.

A

peptidoglycan itself, but rather the degree of crosslinking in the peptidoglycan

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24
Q

What is “gram variable”?

A

In older cultures of G+ organisms, autolytic enzymes have partially digested the peptidoglycan so the G+ will stain pink.
G- NEVER stain purple.

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25
Q

What specific part of the cell wall do lysozymes cleave?

A

Lysozymes cleave the B1,4 linkage between N-acetyl-muramic acid and N-acetyl-glucosamine

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26
Q

How specifically does penicillin disrupt the G+ cell wall?

A

Polysaccharide chains of N-acetyl muramic acid and N-acetyl glucosamine are crosslinked to each other via pentaglycine bridges.
Penecillin inhibits the crosslinking reaction

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27
Q

What are the basic structural units of peptidoglycan?

A

N-acetyl muramic acid and N-acetyl glucosamine held together by B (1,4) linkage.
Pentaglycine bridges allow crosslinking of these polysaccharides.
D- amino acid tetrapeptides linked to muramic acid to create a lattice

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28
Q

What is the internal osmotic pressure of a bacterial cell?

A

5-20 atm (higher than the external environment)

Resistance to this pressure is provided by the peptidoglycan cell wall which provides rigidity

29
Q

What are two major disruptions to the bacterial cell wall?

Where is each site of action?

A
  1. Lysozymes in tears, saliva, WBC break the B(1,4) linkage between N-acetyl muramic acid and N-acetyl glucosamine
  2. Penicillin disrupts the crosslinking reaction of the pentaglycine bridges
30
Q

What are teichoic acids repeating units of?
What do they attach to?
What type of cell (G+ or G-) contains these?

A

Teichoic acids are repeating units of:
1. ribitol phosphate and
2. glycerol phosphate
joined by phosphodiester bonds.

Teichoic acids attach to:

  1. N-acetyl glucosamine or N-acetyl muramic acid (wall teichoic acids)
  2. membrane glycolipid (membrane teichoic acids or lipoteichoic acids).

They are found in G+ only!

31
Q

What is the major surface antigen of G+ bacteria?

What is the major surface antigen of G- bacteria?

A 
G+ = teichoic acid
G- = LPS
32
Q

What determines the variety of antigenic types of teichoic acids?

A

They have different degrees and types of substituents attached to the free hydroxyls

33
Q

What are the two major functions of teichoic acid on G+ bacteria?

A
  1. Antigen

2. Bacteriophage receptors (specifically on Bacillus and Staphylococcus)

34
Q

Describe the membrane/cell wall structure of a G- bacteria.

A

They have:

  1. inner membrane- phospholipids with proteins
  2. Periplasmic space- cell wall, binding proteins, lipoproteins
  3. Outer membrane- phospholipid with proteins, porins and LPS
35
Q

What would you find anchored in the outer membrane of a G- bacteria?

A
  1. Proteins
  2. Porins
  3. LPS
36
Q

Lipopolysaccharide (LPS) is the major antigenic determinant of G- bacteria. It is also the ________ of G- meaning that it causes a vast array of infections.

A

endotoxin

37
Q

What is found in the periplasmic space of G- bacteria?

A
  1. lysozomal-like enzymes
  2. Hydrolytic enzymes
  3. Lipoprotein
38
Q

What are the three regions of LPS?

A
  1. Lipid A (toxic moiety)
  2. Core polysaccharide (homologous in certain strains like salmonella)
  3. O antigen (species/serotype antigen)
39
Q

In G- bacteria, the O-antigen very often determines the __________ and ________ of the bacterial strain.

For example, in cholera, there are 137 strains and only two, _____ and _____ are virulent.

A

virulence and antigenicity

O1 and 0139

40
Q

Virulent colonies are also called ________ because of their appearance.

A

Smooth- because they have wet mucoid colonies on agar plates.

41
Q

Bacteria that do not have ___________ are typically not virulent and are referred to as ________ because of their appearance on agar.

A

O-antigens, rough

42
Q

How could one claim that O-antigens and teichoic acids are similar?

A

They are the G- and G+ bacteriophage receptors respectively.

Both are the major antigenic portions of their respective bacteria type

43
Q

If the cell wall is removed with penecillin, what will happen to the cell?

A

It will lyse because the osmotic pressure is too high unless the osmotic pressure of the medium is raised (20% sucrose or 0.3-0.5M KCl)

44
Q

The osmotically sensitive sphere formed after treatment with lysozyme is called ________ for G- and _______ for G+ bacteria.

A 
G- = spheroplast (partial retention of cell wall because of outer membrane protection)
G+ = protoplast (free of cell wall)
45
Q

What type of bacteria is “protoplast-like” because they are devoid of a peptidoglycan cell wall?

A

mycoplasma

46
Q

What type of cells have capsules?
What is the purpose of a capsule?
What are most capsules composed of? (give the notable exception)

A
  1. G+ or G-
  2. Resist phagocytosis, K antigens
  3. polysaccharides except Bacillus anthracis which uses polyglutamic acid
47
Q

What are the four most notable examples of bacteria with capsules?

A
  1. Streptococcus pneumoniae (G+ cocci)
  2. Klebsiella pneumonia (G- rod)
  3. Haemophilus influenza (G- rod)
  4. Neisseria meningitidis (G- cocci)
48
Q

What is used to classify the 70 serotypes of pneumococcal bacteria?

A

The different sugars and linkage in the capsules

49
Q

What is the size of flagella? Why is this significant?

A

They are 3-12microns in length

Bacteria are only 0.2-2microns in diameter so the flagella is larger than the bacteria itself!

50
Q

What is it called when the flagella are at both ends?

When the flagella goes all the way around?

A

Both ends = polar

all the way around = peritrichous

51
Q

What are:
O-antigens
K-antigens
H-antigens

A 
O = LPS 
K= capsular
H= flagellar
52
Q

What are flagella composed of?

A

identical subunits of single proteins called flagellin.

Different AA primary structure determines the different antigens

53
Q

What are pili? What is their main function?

A

They are short hair-like projections that surround the bacteria.
They are a virulence factor because they promote adhesion to host cells

54
Q

What is F-pilus?

A

a long extension that can transfer plasmids/ genes from one bacteria to another via conjugation

55
Q

Bacteria that do not have ___________ are typically not virulent and are referred to as ________ because of their appearance on agar.

A

O-antigens, rough

56
Q

How could one claim that O-antigens and teichoic acids are similar?

A

They are the G- and G+ bacteriophage receptors respectively.

Both are the major antigenic portions of their respective bacteria type

57
Q

If the cell wall is removed with penecillin, what will happen to the cell?

A

It will lyse because the osmotic pressure is too high unless the osmotic pressure of the medium is raised (20% sucrose or 0.3-0.5M KCl)

58
Q

The osmotically sensitive sphere formed after treatment with lysozyme is called ________ for G- and _______ for G+ bacteria.

A 
G- = spheroplast (partial retention of cell wall because of outer membrane protection)
G+ = protoplast (free of cell wall)
59
Q

What type of bacteria is “protoplast-like” because they are devoid of a peptidoglycan cell wall?

A

mycoplasma

60
Q

What type of cells have capsules?
What is the purpose of a capsule?
What are most capsules composed of? (give the notable exception)

A
  1. G+ or G-
  2. Resist phagocytosis, K antigens
  3. polysaccharides except Bacillus anthracis which uses polyglutamic acid
61
Q

What are the four most notable examples of bacteria with capsules?

A
  1. Streptococcus pneumoniae (G+ cocci)
  2. Klebsiella pneumonia (G- rod)
  3. Haemophilus influenza (G- rod)
  4. Neisseria meningitidis (G- cocci)
62
Q

What is used to classify the 70 serotypes of pneumococcal bacteria?

A

The different sugars and linkage in the capsules

63
Q

What is the size of flagella? Why is this significant?

A

They are 3-12microns in length

Bacteria are only 0.2-2microns in diameter so the flagella is larger than the bacteria itself!

64
Q

What is it called when the flagella are at both ends?

When the flagella goes all the way around?

A

Both ends = polar

all the way around = peritrichous

65
Q

What are:
O-antigens
K-antigens
H-antigens

A 
O = LPS 
K= capsular
H= flagellar
66
Q

What are flagella composed of?

A

identical subunits of single proteins called flagellin.

Different AA primary structure determines the different antigens

67
Q

What are pili? What is their main function?

A

They are short hair-like projections that surround the bacteria.
They are a virulence factor because they promote adhesion to host cells

68
Q

What is F-pilus?

A

a long extension that can transfer plasmids/ genes from one bacteria to another via conjugation

Bugs and Drugs (21 decks)

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