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ID Exam I > Bacterial Structure > Flashcards

Bacterial Structure Flashcards

1
Q

Cocci =

A

Spheres

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2
Q

Pairs of Cocci =

A

Diplo

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3
Q

Chain of Cocci =

A

Strepto

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4
Q

Clump of Cocci =

A

Staph

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5
Q

Bacilli =

A

Rods

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6
Q

Vibrio =

A

Curved

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7
Q

Spiral =

A

Spirillum or Spirochete

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8
Q

Gram Stain

A

Crystal Violet → Iodine Wash → Alcohol decolorant → Safranin Red

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9
Q

Positive Gram Stain

A

Retains blue dye in thick cell wall

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10
Q

Negative Gram Stain

A

Stain washed away from thin cell wall and red is visible

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11
Q

>70% same DNA =

A

Same species

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12
Q

>97% same species =

A

Same rRNA

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13
Q

Phenotypic Classification

A
  • Morphology
  • Gram stain
  • Markers (fermentation, enzymes, hemolysis), motility
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14
Q

Genotypic Classification

A
  • Variable GC content
  • 16S rRNA sequence
  • Used to track outbreaks
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15
Q

Nucleoid

A

Circular haploid chromosome

  • No Nuclear membrane
  • 70S Ribosome
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16
Q

Plasmids

A

Small, circular DNA molecules outside chromosome

Transmissible and non-essential

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17
Q

Inner membrane

A

Lipid bilayer w/o sterols

  • ETC
  • ATP synthesis
  • Flagella
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18
Q

Cell wall

A
  • Peptidoglycan
  • Thicker and stains blue in Gram (+)
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19
Q

Peptidoglycan

A

Alternating NAG (N-acetylglucosamine) and NAM (N-acetylmuramic acid) with peptide cross link

Composes rigid wall

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20
Q

Gram (+)

A
  • Multilayered peptidoglycan with many proteins covalently attached
  • Techoic Acid
  • Lipoteichoic Acid
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21
Q

Techoic Acid:

A

Glycerol or ribitol phosphate polymer with D-ala or sugar

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22
Q

Lipoteichoic Acid

A

Teichoic acid terminated with a glycolipid anchored to the membrane

-Induces inflammation and septic shock (like LPS)

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23
Q

Gram (-)

A

Thin peptidoglycan layer and outer membrane

Outer membrane contains lipopolysaccharides and porins

Porins allow passage of small hydrophilic molecules

24
Q

Outer Membrane of Gram (-) Bacteria

A
  • Contains LPS (endotoxin)
  • Consists of 3 regions: lipid A, core polysaccharide, and O polysaccharide (O-antigen changes here responsible for many serotypes)
  • Potent stimulator of immune system
25
Q

Peptides are attached to

A

NAM

26
Q

Peptidoglycan is site of action for

A

Penicillin

Cephalosporins

27
Q

Acid-fast cell walls

A

Related to Gram (+) but have mycolic acid (waxy lipid in something resembling outer membrane) and arabinogalactan.

Requires special acid-fast staining technique.

Includes Mycobacterium and Nocardia.

28
Q

Lack cell wall

A

Mycoplasma and Ureaplasma

29
Q

Permeability Hierarchy

A

Mycoplasma > Gram(+) >Gram(-) >Acid-fast

30
Q

Gram Positive Bacteria

A
  • Lipoteichoic Acid (LTA)
  • Major surface antigen for immune reaction
  • Induces cytokine release
  • Binds antibodies → activates complement cascade
31
Q

Periplasm: Gram (-)

A
  • Space between cell membrane and outer membrane
  • Contains many enzymes
  • Beta-lactamase → inactivates many antibiotics
32
Q

Outer Membrane: Gram (-)

A
  • Contains outer layer of lipopolysaccharide (LPS)
  • Major immune trigger for gram (-) bacteria
33
Q

Lipopolysaccharide: Gram (-)

A
  • Components: polysaccharide, lipid A, O antigen
  • Lipid A: highly toxic and triggers cytokine release
  • O antigen: target for antibodies
34
Q

Surface antigens that trigger immune response in Gram (+)

A
  • Cell wall and membrane
  • Lipoteichoic acid (LTA)
35
Q

Surface antigen that triggers immune response in Gram (-) bacteria

A
  • Outer membrane
  • Lipopolysaccharide (LPS)
36
Q

Capsule

A
  • Sticky, gelatinous layer secreted by bacteria
  • Helps attach to host cells
  • Protects against phagocytosis
  • Mostly water with some polysaccharide
37
Q

Anthrax Capsule

A

Made of protein (d-glutamate)

Virulence factor that allows for unimpeded growth

38
Q

Capsules and Immunology

A
  • B-cells secrete capsular antibodies (IgG) which bind to capsule (tag bacteria for phagocytosis)
  • Phagocytes recognize bacteria via Fc receptors
  • Antibodies can also bind complement cascade. Leads to formation of MAC which leads to cell death or formation of opsonin (C3b protein) which can form on capsule surfaces. This drags in phagocytes to destroy bacteria.
39
Q

Loss of antibodies/B-cells or complement results in

A

Recurrent encapsulated bacterial infections

40
Q

Asplenia

A
  • Risk of sepsis from encapsulated bacteria due to loss of splenic phagocytes (consume these bacteria after they are tagged with antibodies)
  • Splenectomy or SS Anemia (functionally asplenic)
41
Q

Capsular Vaccines

A
  • Capsular polysaccharides are basis for many vaccines
  • Polysaccharides in capsule often weakly immunogenic so they are conjugated to another protein that stimulates a greater immune response
42
Q

Capsules

A

Protection: poorly antigenic and anti-phagocytic

43
Q

Flagella

A

Locomotion

44
Q

Adhesins

A

Pili and other surface proteins aid attachment of bacteria to eukaryotic cells

45
Q

Sex pili

A

Transfer genetic info

46
Q

Secretion organelles

A

T3SS, T4SS

47
Q

Antigens

A
  • LPS (O-antigen)
  • Flagella
  • Teichoic acids
  • Capsule
  • Potentially any surface protein
48
Q

Exotoxins

A

Secreted proteins

  1. Cytolytic enzymes: hemolysins, pore formers, phospholipases
  2. A-B toxins: cholera, shiga, tetanus, botulinum, anthrax (B protein binds to cell and A protein enters cell)
  3. Superantigens: Staph. Exotoxin -toxic shock syndrome toxin; nonspecific activation of T cells
  4. Enterotoxins: Target intestines
49
Q

Endotoxins and cell wall components

A

LPS

Teichoic acids

PG fragments

50
Q

Bacteriophage

A
  • Bacterial viruses
  • Lytic: produce progeny and lyse cell
  • Lysogenic: phage DNA integrated into bacterial chromosome; dormant, but can be reactivated.
  • Phage conversion: phage carries virulence genes (toxins)
51
Q

Superantigens

A

Toxic shock syndrome

52
Q

Spores

A
  • Not metabolically active, survive harsh environment and nutrient depletion, not for reproduction
  • Bacteria: produced by bacilli and clostridia, ex: anthrax, botulinum, food poisoning, C. diff
  • Clinical: resistance to treatment and steriliation, requires autoclave
53
Q

Pili in E. Coli

A

Allow attachment to urinary tract. Cause UTIs and pyelonephritis.

54
Q

Pili in Neisseria Gonorrhea

A

Exhibit antigenic variation: Past infection may not result in immunity to future infection

55
Q

Ribosomes

A
  • Site of protein synthesis in bacteria
  • Subunits: 50S and 30S
  • Tetracyclines bind to 30S
  • Aminoglycosides interfere with 30S protein synthesis

ID Exam I (3 decks)

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