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H&D > Wk 1 Bacteriology 1 & 2 > Flashcards

Wk 1 Bacteriology 1 & 2 Flashcards

1
Q

Phylogenetic Tree of Life

A
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2
Q

Human-associated microbiota

A
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3
Q

What is colonization resistance?

A

microbiota inhibits colonization by newcomers
-high diversity and density -> high CR

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4
Q

How are bacteria named?

A

each organism gets 2 names:
1. Genus is the first name, always capitalized
2. species is second, not capitalized

-both either underlined or italicized
-“species” is singular and plural

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5
Q

Taxonomy of bacteria

A

Domain
Phylum
Class
Order
Family
Genus
Species
Strain

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6
Q

What do eukaryotic and bacterial cells have in common?

A
  1. cell membrane
  2. cytoplasm
  3. ribosomes
  4. DNA
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7
Q

What do bacteria cells have that eukaryotic cells don’t?

A
  1. simple structure
  2. no prominent nucleus
  3. circular DNA
  4. single, haploid chromosome
  5. small size
  6. cell wall w/ peptidoglycan
  7. 70S ribosomes
  8. no organelles
  9. cells divide by binary fission
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8
Q

What do eukaryotic cells have that bacteria cells don’t?

A
  1. complex structures
  2. prominent nucleus
  3. linear DNA
  4. paired diploid chromosome
  5. large size
  6. cell wall (chitin, cellulose)
  7. 80S ribosomes
  8. membrane-bound organelles
  9. cell division by mitosis
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9
Q

Compare eukaryotic and bacterial cells

A
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10
Q

What are 3 ways to classify bacteria?

A
  1. morphology
  2. cell wall structure - Gram staining
  3. Oxygen requirements and metabolism
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11
Q

What is the role of peptidoglycan?

A

Main structural component of the bacterial cell wall

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12
Q

What is -emia?

A

In the blood

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13
Q

Mycoplasma

A

Bacteria with NO cell wall

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14
Q

acid-fast bacteria

A

-resist decolorization
*Mycobacteria and Nocardia *

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15
Q

Functions of bacterial cell wall

A

-multilayered structure
-provides structural integrity
-allows nutrients/waste transport
-rigid, determines shape
-respiratory chains
-adhesions
-basis for serotyping pathogens: Antigens: O (LPS), K (capsule), H (flagellin)

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16
Q

What are the parts of a LPS?

A

=lipopolysaccharide (integral for Gram-negative bacteria)
1. Lipid A - region (endotoxin), conserved, responsible for fever and shock
2. Core oligosaccharide of 5 sugars
3. O antigen - immunogenic and accounts for virulence of Gram-negative bacteria

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17
Q

Mycobacteria

A

Does not stain or stains weakly Gram-positive
-cell wall has high lipid content - mycolic acids and lipoarabinomannan (LAM), a glycolipid

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18
Q

Bacterial Metabolism

A
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19
Q

Energy Production in Bacteria

A
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20
Q

What are obligate aerobes?

A

require oxygen

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21
Q

What are facultative anaerobes?

A

can grow w/ or w/o oxygen
-some can carry out anaerobic respiration by using alternate electron acceptors

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22
Q

Microaerophilic bacteria

A

Can survive in very low levels of O2

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23
Q

Obligate Anaerobes

A

Are poisoned by oxygen

24
Q

How are aerobic and anaerobic bacteria identified?

A

Grow them in test tubes of thioglycolate broth

25
Q

How are aerobic or facultative bacteria determined?

A

Are catalase positive

26
Q

What bacterial cell structures contribute to virulence?

A
  1. protein secretion systems
  2. toxins
  3. flagella
  4. adhesins: pili and fimbriae
  5. capsules
  6. spores
27
Q

What are protein secretion systems?

A

Proteins with toxins synthesized by bacteria, secreted by specialized structures w/ syringe-like injectors (AKA injectosome or a needle-like protein)

28
Q

What are exotoxins?

A

usually secreted by bacteria, sometimes by lysis of the bacterial cell
-enter eukaryotic cells through receptor-mediated endocytosis
-virulent strains produce toxin = major determinant of virulence
-many are pore-forming molecules w/ A-B components (B=binding, triggers endocytosis and A=active, enzyme activity)

29
Q

Endotoxins

A

=cell-associated substances that are structural components of the outer membrane (LPS) of Gram-negative bacteria
-released from growing bacterial cells
-released from cells lysed from effective host defense (eg lysozyme)
-released from activities of certain antibiotics (eg penicillin)

30
Q

5 types of exotoxins

A
  1. enterotoxins - act in GI tract -> diarrhea
  2. Neurotoxin -> paralysis
  3. pyrogenic exotoxins ->cytokine release -> rash, fever, toxic shock syndrome (eg Superantigens)
  4. Tissue invasive exotoxins - allow bacteria to penetrate or circumvent cell and tissue barriers (eg DNAses, pore-forming toxins)
  5. others: there are many. Can affect very specific host factors, cell signaling mechanism, protein synthesis
31
Q

Superantigens

A

-Bind to MHC class II of antigen presenting cells and activate T cell receptor
-Massive and uncontrolled release of cytokines (TNF, IL-1, IL-6, IFN-γ)
-Nitric oxide release →capillary leak →toxic shock

32
Q

2 examples of superantigens

A

Toxic shock syndrome toxin (TSST-1)
* Staphylococcus aureus
* Excessive cytokine production leads to fever, rash, toxic shock and vascular rash
* Scalded skin syndrome and food poisoning
Streptococcal pyrogenic exotoxin A
* Streptococcus pyogenes
* Toxic shock-like syndrome, fever, rash, shock, scarlet fever

33
Q

Characteristics of endotoxins

A
  • Lipopolysaccharide in the cell walls of Gram- negative organisms
  • Heat-stable
  • Released into the body
  • Via cell lysis or detachment
  • Not actively secreted (unlike exotoxins)
  • Bacterial lysis due to antibiotic treatment
  • Hyper-inflammation can lead to Sepsis and Septic shock, Organ failure, Acute respiratory syndrome
34
Q

Exotoxins vs Endotoxins

A
35
Q

What are flagella?

A

facilitate motility and adhesion
-imp virulence factors (H antigen)
-ex Helicobacter pylori, E. coli, spirochetes

36
Q

What are bacterial adhesins?

A

Bacterial adhesin proteins are often associated with hair-like fibers called pili or fimbriae
-Can act as receptors for phage, promote conjugation (genetic exchange), and mediate biofilm formation
- Anti-adhesins being developed as anti- bacterial therapeutics

37
Q

What is biofilm?

A

A colony of same species of bacteria w/ protection from external environment
-promote bacterial colonization and persistence

38
Q

Bacterial capsules

A
  • Layers of polysaccharide (or polypeptide) associated with the bacterial surface, made of K antigen
    -protection
    -antibodies against specific capsule K antigen
    -main component of some vaccines
39
Q

What are 5 encapsulated bacteria that are opsonized and then cleared by the spleen?

A
  • Streptococcus pneumoniae * Hemophilus influenzae
  • Neisseria meningitidis
  • Escherichia coli
  • Salmonella typhi
  • Klebsiella pneumoniae
40
Q

What are spores?

A
  • Some Gram-positive bacteria can form spores
  • Spores form when there is shortage of nutrients
  • Spores lack metabolic activity
  • Core contains dipicolonic acid (heat resistance)
    -pretty inert and resistant to antimicrobials
    ex C. difficile
    -most antibiotics will not kill spores (neither will hand sanitizers)
41
Q

Medically important spore-forming bacteria

A
42
Q

Bacterial cell replication

A

Binary fission:
1. DNA replication
2. chromosome segregation
3. cytokinesis

43
Q

What are the phases of binary fission?

A
  1. lag phase- metabolic activity, no division
  2. log phase - rapid cell division
  3. stationary phase - nutrients depleted, growth slows, spores form
  4. death phase - waste products accumulate ->death
44
Q

How do transcription and translation occur in bacterial cells?

A

They are coupled and occur at the same time

45
Q

What are 4 methods of genetic exchange for bacteria?

A
  1. transformation
  2. conjugation
  3. transduction
  4. transposition

Horizontal Gene Transfer (HGT) allows for the rapid exchange and spread of virulence determinants and antibiotic resistance genes.

46
Q

What changes in DNA base sequences -> altered phenotypes?

A
  1. base substitution
  2. frameshift
  3. transposons (insertion sequence)
47
Q

What do altered bacterial genetics allow for?

A
  1. antibiotic resistance
  2. transfer of antibiotic resistance genes
  3. evade host immune system
48
Q

What is horizontal gene transfer (HGT)

A
  1. transformation
  2. transduction
  3. conjugation
49
Q

What is bacterial transformation?

A

DNA is taken up directly by cells.
* Bacteria able to take up DNA are said to be
“competent”.

50
Q

What is transduction?

A

=transfer of DNA mediated by bacteriophages
-viruses that replicate w/in bacteria
-found wherever bacteria is found

51
Q

What is the phage life cycle?

A

Lytic and lysogenic phases
-prophage can carry important fitness and virulence determinants

52
Q

What is conjugation?

A

Add description
-uses sex pili

53
Q

What are 4 plasmid types?

A

Fertility F-plasmids: contain tra genes for transfer. They are capable of conjugation and result in the expression of sex pili.
Col plasmids: contain genes that code for bacteriocins (proteins that can kill other bacteria). Some are also toxic to host cells (genotoxins)
Virulence plasmids: encode virulence factors, can convert a bacterium into a pathogen. (e.g. pathogenic Salmonella strains)
Resistance (R) plasmids: contain genes that provide resistance against antibiotics or poisons. Historically known as R-factors, before the nature of plasmids was understood.

54
Q

What is transposition?

A

Transposable elements allow for gene transfer, transposon movement, can carry virulence and antibiotic-resistance genes

55
Q

What do capsules protect from?

A

phagocytosis

H&D (23 decks)

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