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BMR 605 > Test 1 Bacterial Growth and Virulence > Flashcards

Test 1 Bacterial Growth and Virulence Flashcards

1
Q

What are the 4 Bacterial Growth environments?

A
  • Obligate anaerobes: Only use fermentation, sugar to acds, make less ATPs.
  • Obligate aerobes: Only use respiration, require oxygen, makes ATPs
  • Facultative anaerobes: Use both respiration and fermentation, E. Coli, Strep and Staph
  • Intracellular Bacteria
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2
Q

What is the role of Superoxide Dismutase (SOD) & Catalase?

A
  • Enzymes of aerobic bacteria
  • Superoxide radical (O2-) produced by bacterial metabolism
  • SOD converts O2- to O2 or to H2O2
  • Catalase converts H2O2 to oxygen and water
  • Needs these enzymes to survive in oxygen environment
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3
Q

Provide Details about Obligate Aerobes?

A
  • Use oxygen to generate ATP
  • Oxygen is final electron acceptor during respiration
  • Respiration equals to ETS
  • Contain SOD (Superoxide dismutase)
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4
Q

What are the Key bacteria that are obligate aerobes?

A
  • Pseudomonas aeruginosa (but can use nitrate as electron acceptor via respiration, anaerobe)
  • Mycobacterium tuberculosis
  • Nocardia (opportunistic infections)
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5
Q

Provide details about Obligate anaerobes?

A
  • Use Fermentation (no Oxygen)
  • By products are often gases like CO2 or H2
  • Produce short chain fatty acids (SCFA), acetic acids, proionic acid, butyric and isobutyric acids, “foul smell”.
  • Often present in dental abscesses.
  • Live near mucosal surfaces
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6
Q

What are the Key bacteria of the obligate anaerobes?

A

Actinomyces, Bacterioides, Clostridium

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7
Q

What three Bacterial Virulence Factors promote colonization and survival within the host?

A

Adherence, Invasion, Survival

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8
Q

Bacterial Virulence Factors that cause damage to host cells.

A

Endotoxin, Exotoxin, superantigens

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9
Q

What are the two methods of adherence?

A
  1. Pili (fimbriae)
  2. Biofilms
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10
Q

Describe the structure and function of Pili?

A
  • Pili (fimbriae): rod-shaped structures
  • Tip mediates attachment by binding to a host receptor (either glycoprotein or glycolipid)
  • Neisseria fimbriae bind GD1 ganglioside on host.
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11
Q

Describe the Structure and function of Biofilms

A
  • Formations of dense, multiorganism layers on a surface
  • Especially significant in implants, catheters, or indewelling devices.
    • E. coli causing cystitis (bladder infection) in hospitals (via catheters).
    • Staph. epidermidis colonization of heart implants are serious clinical problems.
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12
Q

Describe Induced phagocytosis?

A
  • Entry into host cells that are not naturally phagocytic
    • Bacterial surface proteins (invasins) induce rearrangments in the actin cytoskeleton
    • Forms a pseudopod-like structure, which mediates bacterial engulfment.
  • This is desirable to the bacteria.
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13
Q

What are invasins?

A

Bacterial surface proteins that induce rearrangments in the actin skeleton.

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14
Q

How do bacteria survive phagocytosis?

A

Production of catalase + SOD

Lysozyme resistant cell wall

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15
Q

How do bacteria escape from phagocytic vesicles?

A
  • Some are able to survive ingestion by macrophages.
  • Involves escape from phagocytic vesicle + advantages associated with an intracellular life.
  • A bacterial protein disrupts the vesicle membrane that allows escape.
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16
Q

How do Bacteria aquire iron for colonization and survival?

(3 Mechanisms)

A
  • Iron is present in low concentrations in the host therefore bacteria use:
    • Siderophores chelate iron effectively and bring inside cell.
    • Some bacteria have receptors for transferrin.
    • Cytotoxins which damage/kill host cells act to liberate intracellular nutrients, including iron.
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17
Q

In what general ways do bacteria evade the immune system?

A
  • Capsules and slime layers cover entire cell.
  • Network of polymers helps bacterial cell evade complement and phagocytes.
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18
Q

What is the mechanism for evading the antibody response?

A
  • Antigenic switching
    • H1/H2 pilus switching in Salmonella
    • Antigen variation in treponemes
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19
Q

Virulence factors that damage host cells?

A
  • Exotoxins are bacterial proteins that are toxic to host cells
    • Many (but not all) are secreted into surrounding medium
    • Some G- exotoxins remain in periplasm
    • Contrast with endotoxin = LPS in outer membrane of gram-negative bacteria
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20
Q

What are the three major types of Exotoxins?

A

AB toxins, hemolysins (pore formers), and superantigens.

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21
Q

Describe the functions and structures of AB Toxins

A
  • B subunit promotes binding to the host cell
  • A subunit has enzymatic activity
  • Example: diptheria toxin ADP - Ribosylates host EF-2 protein and shuts down protein synthesis.
  • A and B subunits bound by disulfide bonds.
22
Q

Mechanism of AB toxin

A
  1. Inhibition of Protein Synthesis
  2. Hyperactivation
  3. Effects on nerve-muscle transmission
23
Q

What are cytolysins and what do they do?

A
  • They are Pore formers, that allow water to enter and ions to escape.
  • Phospholipases
    • Cleave hydrophobic portion away from charged head group
    • Destabilize membrane and cell lyses
24
Q

How do bacteria perturb host defenses.

A
  • In some cases host disease is not caused by virulence factors intrinsic to the infectious agent but result from the microbe’s ability to alter host immune functions.
    • These alterations can effect the immune system and result in:
      • Autoimmune activation by bacterial proteins
      • Elaboration of bacterial superantigens
25
Q

How does autoimmune activation function?

A
  • Microbe produces proteins or polysaccharides which possess antigenic determinants (epitopes) which are similar to host proteins (molecular or antigenic mimicry).
    • AB response to campylobacter is directed against LOS which has structural similarity to peripheral neuron surface structures.
    • Host cells or anatomical structures are destroyed.
      • E.g. myelin sheath destruction in Guillian-Barre Syndrome.
26
Q

Elaboration of superantigens

A
  • Bacteria can produce an antigen which binds to the MHC class 2 on antigen presenting cells (APC).
    • This protein also binds to TCR:
      • Which results in 1 in 5 T cells are activated and release IFN-y and IL-2
    • Examples:
      • Staphylococcal toxic shock syndrome toxin (TSST)
      • Staphylococcal enterotoxins
      • Erythrogenic toxin A or C of S. pyogenes.
    • Massive vasodilation and shock.
27
Q

Details about endotoxin/septic shock

A
  • Bacterial products (like LPS) hyperactivate the complement cascade and other pathways leading to shock/hypotension, DIC and organ failure.
  • Host responses are presumably protective with small doses of LPS, but can cause major damage systemically when LPS is present in excess.
  • LPS is active and recognized when bacterium is lysed.
28
Q

What are the main concepts of Bacterial Nutrition?

A
  • Nutritional requirements for microbial growth
  • Extracellular protein transport
  • Metabolite transport system (small molecules)
29
Q

Basic Nutrients of Bacterial species:

A
  • Glucose
  • NH4+
  • Mg-2
  • Mn-2
  • SO4+2
  • PO4+3
  • Other trace ions
30
Q

Addition nutrient requirements for Escherichia coli

A

NONE

31
Q

Addition nutrient requirements for Salmonella typhi

A

Tryptophan

32
Q

Addition nutrient requirements for Staphylococcus aureus?

A

Nicotinic Acid, Thiamine, 10 amino acids

33
Q

Addition nutrient requirements for Leuconostoc paramesenteroides?

A
  • Nicotinic acid, Thiamine, Pantothenic acid, Pyridoxal, Riboflavin, Cobalamin, Biotin, Folate, Guanine, Adenine, Uracil, 16 amino acids.
34
Q

Defining feature of Prototrophs?

A

No nutrient requirements beyond simple carbon, nitrogen, and sulfur sources.

35
Q

Defining feature of Auxotrophs?

A

Those organisms that require precursor molecules added to the growth medium.

36
Q

How do bacteria uptake nutrients?

A
  • Small molecules: Freely diffusible while others require a specialized system for uptake.
  • Macromolecules: Too large to diffuse, so exoenzymes break them down.
37
Q

What does the General Secretory System (GSS) do?

A
  • G+ :transports proteins to the extracellular space
  • G- : To the periplasm
    • G- require a second system to get outside the cell.
38
Q

Describe the GSS mechanism

A
  1. GSS complex located in cytoplasmic membrane recognizes precursor protein with signal peptide.
  2. Precursor protein passes through the complex
  3. Signal peptide is cleaved off and protein folds into final shape.
39
Q

What is the defining feature of Sec-dependent?

A

Some of these systems require the GSS to deliver protein to periplasm.

Types: V, II

40
Q

What is the defining feature of Sec-independent?

A

Multiprotein complexes that span the inner and outer membrane.

Types: IV, III, I

41
Q

What is the defining feature of the Type III system, and where is it observed?

A
  • Acts like a molecular syringe which injects effector proteins into the host cell cytoplasm upon contact with the host cell surface.
    • Present in Salmonella, Shigella, Yersinia, and Pseudomonas
42
Q

What are Exoenzymes?

A
  • Some exoenzymes are virulence factors because they improve the organism’s ability to invade, colonize, multiply and/or cause disease in the host.
    • ​Examples:
      • Streptococcus
      • Staphylococcus
      • Clostridium spp.
43
Q

What is facilitated diffusion?

A
  • Transport is mediated by the protein found in the cytoplasmic/inner membrane:
    • energy independent, but subsequent steps may use ATP.
    • ATP-dependent kinase catalyzes phosphorylation of glycerol (putting a charge on it) and effectively trapping the molecule inside the cell.
44
Q

What is Active Transport?

A
  • Most uncharged molecules larger than glycerol and all ionized molecules require energy for transport.
  • In Active transport substrates are moved against concentration gradient.
    • This requires energy.
45
Q

What are the three Active transport systems?

A
  • Proton gradient active transport
  • ATP-dependent active transport
  • Group translocation (PTS)
46
Q

Describe Proton gradient active transport?

A
  • Required energy is derived from pumping of protons
  • Uses more energy than group translocation
  • lacY permease
47
Q

Describe ATP-Dependent active transport?

A
  • Galactose transport is osmotic shock sensitive because gal protein is in the periplasmic space.
  • Also uses more energy than group translocation.
48
Q

Describe Group Translocation (PTS)?

A
  • AKA PEP: Sugar Phosphotransferase system (PTS) a mechanism of the transport of glucose and other sugars.
  • Works by trapping a sugar-phosphate within the cell.
  • The PTS consists of a complex of phosphotransferase proteins (Enzyme I, Enzyme III and Enzyme II) which transfer phosphate groups from PEP ultimately to sugar as it crosses the cytoplasmic membrane.
49
Q

What is a key regulator of glucose effect?

A

Phosphorylated-IIIglc (a component of PTS).

50
Q

What are Siderophores and what are their two subtypes?

A
  • Macromolecules that bind iron in the medium and transport it inside the cell.
  • Two Types:
    • ​Enterobactin (enterochelin)
    • Hydroxamate
51
Q
A
52
Q
A

BMR 605 (10 decks)

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