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Microbiology Exam 1 > Introduction to Microbiology > Flashcards

Introduction to Microbiology Flashcards

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1
Q

What are the sizes of Viruses and Bacteria, and what type of microscope is used to view them?

A

Viruses (0.03-0.3 microns; Electron-light microscope)

Bacteria (0.1-10 microns; Light microscope)

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2
Q

Unique Features: Viruses

A

Smallest infectious particles

Require host for replication

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3
Q

Unique Features: Bacteria

A

Simple unicellular organisms

Prokaryotes

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4
Q

Unique Features: Fungi

A

More complex
Eukaryotes
Unicellular (yeast) or filamentous (mold)

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5
Q

Unique Features: Parasites

A

Most complex
Eukaryotes
Unicellular to multicellular

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6
Q

What is unique about prokaryotes compared to eukaryotes?

A
  1. No nucleus
  2. Single, double-stranded, circular DNA chromosome (Haploid)
  3. Smaller ribosome (70s)
  4. Mesh-like peptidoglycan cell wall
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7
Q

Classification of Bacteria (4 things)

A
  1. Visible features (shape, spore formation, gram reaction)
  2. Nutrition (growth media, aerobic vs anaerobic, temperature for optimal growth)
  3. End products (production of specific enzymes/toxins)
  4. Surface molecules (antigen composition)

***Currently developing a more rigid classification system by nucleic acid analysis (PCR, nucleic acid homology, and gene probes)

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8
Q

What are the shapes of Cocci, Bacilli, and Spirochetes?

A

Cocci (spherical)
Bacilli (rod; straight or curved)
Spirochetes (spiral)

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9
Q

Are gram positive or gram negative cell walls more simple?

A

Gram Positive

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10
Q

Do gram positive or negative cells stain purple?

A

Positive (Purple = Positive)

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11
Q

Where is the peptidoglycan layer found?

A

Internal to the capsule (if present) and external to the cytoplasmic membrane (not found in Mycoplasma and Chlamydia)

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12
Q

Functions of peptidoglycan

A

Provide protection
Determines shape

Unique to bacteria; both gram positive and gram negative have it

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13
Q

Structure of Peptidoglycan

A
  • Linear chain of alternating N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) with tetra peptide crosslinks
  • Linked via B-1,4 linkages
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14
Q

Where does lysozyme from endothelial cells attack bacteria?

A

At the B-1,4 linkages of the peptidoglycan layer

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15
Q

Proinflammatory effects of Peptidoglycan

A

Fixes Complement
Binds pattern recognition receptors (e.g. Toll-like receptors)
Triggers TNF production

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16
Q

Unique features of gram-positive envelope

A
  1. Thick layer of peptidoglycan (many layers w/ extensive crosslinking)
  2. Teichoic Acid (PG associated; PM associated (Lipoteichoic Acid, LTA))
  3. Various proteins and lipids which differ between bacteria
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17
Q

What are the functions of Teichoic Acid and LTA?

A

Promote attachment of bacteria to other bacteria or host cells (virulence factors)

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18
Q

Unique features of gram-negative envelope

A
  1. Greatly reduced peptidoglycan
  2. PG (peptidoglycan) is within the periplasmic space
  3. Surrounded by an OUTER MEMBRANE rich in porins and endotoxin/LPS (lipopolysaccharide; important pathogen-associated molecular pattern)
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19
Q

Structure of outer membrane of gram-negative envelope

A
  • “Stiff canvas sack”
  • Maintains structure/permeability barrier
  • Rich in porins (allow diffusino of hydrophilic molecules less than 700 Da through)
  • Structural and transport/secretory proteins
  • Asymmetric phospholipid bilayer
20
Q

Inner leaflet vs outer leaflet of Outer Membrane of gram-negative envelope

A

Inner leaflet contains phospholipids

Outer leaflet contains LPS (creates asymmetry of membrane)

21
Q

What are the 3 subunits of LPS/Endotoxin?

A

Lipid A, Core Polysaccharide, O Antigen

22
Q

Lipid A

A
  • Responsible for endotoxin activity of LPS*

- Fatty acids anchor it into outer membrane

23
Q

Core Polysaccharide

A
  • Branched polysaccharide of 9 to 12 sugars

- Required for bacterial structure and viability

24
Q

O Antigen

A
  • Long, linear polysaccharide of repeating saccharide units of 4 to 7 sugars/unit
  • **Helps to classify specific serotypes bacteria due to VARIATION
  • Missing in Neisseria (LOS)
25
Q

How does LPS/Endotoxin cause inflammation/septic shock?

A

Binds CD14 and TLR4 on phagocytes/APCs, which activates the immune system and causes transcription of proinflammatory cytokines (TNF, IL-1, IL-6)

26
Q

Acid-fast Bacteria Characteristics

A
  • Complex cell envelope
  • Mycolic acids (long, branched chain fatty acids) covalently bound to the peptidoglycan via a polysaccharide
  • Other mycolic acid-containing compounds as well as complex lipids form a thick waxy membranous layer outside of the peptidoglycan
27
Q

Examples of Acid-Fast Bacteria

A

Mycobacteria, Nocardia, and Corynebacteria

28
Q

Weakly-stained bacteria

A

Legionella

29
Q

Cell wall too thin to be visible

A

Treponema, Leptospira

30
Q

Wall-less bacteria

A

Mycoplasma

31
Q

Gram Stain Steps

A
  1. Crystal Violet
  2. Gram Iodine
  3. Decolorizer (Alcohol or Acetone)
  4. Safranin Red
32
Q

Acid-Fast Stain Steps

A
  1. Stain all bacteria red by carbol fuchsin
  2. Acid alcohol added to remove stain from everything except those that are Acid-Fast
  3. Methylene blue used to counter-stain and label other bacteria
33
Q

Acid Fast Cell Wall

A
  • Waxy outer wall found on Mycobacteria and Nocardia

- Outermost layer is rich in mycolic acids, which causes a very SLOW GROWING bacteria

34
Q

Acid Fast Structure

A

***Similar to Gram Positive
(Inner plasma membrane overlaid with peptidoglycan and no outer membrane)
-Contains Lipoarabinomannan (LAM), Arabinogalactans, and Mycolic Acid

35
Q

Lipoarabinomannan (LAM)

A

Functionall related to LPS (structure, viability, activates immune system)

36
Q

Arabinogalactans

A

Branched polysaccharides that bind to mycolic acid

37
Q

Mycolic Acid

A

60-90 carbons

-WAXY

38
Q

Pili/Fimbrae (two functions)

A
  • Common or somatic (involved in attachment to epithelial cells; usually called adhesins, lectins, evasins, or aggressins)
  • Sex - only one per cell (involved in gene transfer; usually a plasmid)
39
Q

Important antigen associated with Flagella

A

H-Antigen

40
Q

Flagella function

A

Locomotion; can be located at one or both poles

-Important VIRULENCE FACTOR (if removed, more difficult to cause infection)

41
Q

Important Qualities of Capsule

A
  • Can be present on both gram positive and negative
  • Called slime layer or glycocalyx
  • Hydrophilic
  • Aides in protection from immune system (ANTIPHAGOCYTIC, poorly antigenic, major VIRULENCE FACTOR)
  • Needed to survive in host, not in culture
  • **Capsule + protein conjugate serves as antigen for many vaccines
42
Q

Biofilm

A

An organized community of microbial cells that has a capsule/slime layer over the entire population

43
Q

Quellung reaction

A

Used to detect encapsulated bacteria

44
Q

How are encapsulated bacteria cleared from the body?

A

Opsonized and cleared by the spleen

45
Q

Endospores

A

Only formed by Gram POSITIVE bacteria in harsh environmental conditions (e.g. low nutrition)

  • Bacteria convert to vegetative state
  • Gives rise to a single bacteria when conditions are favorable
46
Q

Endospore Characteristics

A
  • Dehydrated, multishelled structure
  • Contains a complete copy of the chromosome
  • Has minimum proteins and ribosomes
  • High concentration of calcium bound to DIPCOLINIC ACID
  • Inner membrane, two peptidoglycan layers, and an outer keratin-like protein coat
  • Multiple coats make it resistant to many treatments*
47
Q

Endospores: Human pathology

A

-Can be aerosolized (airborne, bioterrorism)
-Difficult to manage in hospital settings, as they can withstand extreme pH, temperature (boiling), radiation, attack by enzymes and chemicals
-Can exist for centuries
Sterilization: Autoclave, 120 degrees C at high pressure for over 20 mins, 70% EtOH, 10% bleach and water

Microbiology Exam 1 (11 decks)

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