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MICRB 265 > Week 10 > Flashcards

Week 10 Flashcards

1
Q

2 ways of bacterial adaptation

A

-mutations
-acquisition of new DNA

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2
Q

Two types of mutations

A

-spontaneous (no external pressure, DNAQ doesn’t proofread properly & mistakes made by DNA pol)
-induced (external pressure, DNA damage, caused by external agents like UV radiation, high temp)

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3
Q

3 methods of DNA acquisition

A

-transformation
-transduction
-conjugation

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4
Q

wildtype strain (def.)

A

strain isolated from nature

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5
Q

mutant (def.)

A

strain with a change in its nucleotide sequence

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6
Q

genotype (def.)

A

the nucleotide sequence of an organism

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7
Q

phenotype (def.)

A

observable properties of an organism

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8
Q

point mutation (def.)

A

single nucleotide change

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9
Q

missense mutation (def.)

A

changes the amino acid

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10
Q

nonsense mutation (def.)

A

introduces a stop codon

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11
Q

silent mutation (def.)

A

change in DNA that produces same amino acid; especially in position 3 of codon

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12
Q

cytosine (common form) base pairs with _____

A

guanine

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13
Q

cytosine (rare form) formed from _____ & base pairs with _____

A

-cytosine that has rearrangement of HB acceptor/donor
-adenine

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14
Q

UV radiation causes which type of DNA damage?

A

pyriminidine dimers between two adjacent nitrogen bases which introduced mutations when DNA is replicated

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15
Q

frameshift mutation (def.)

A

-changes the reading frame, tends to be detrimental to the protein, depending on where it is in the gene
-can be either detrimental or advantageous

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16
Q

insertion (def.)

A

introduces a nucletoide

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17
Q

deletion (def.)

A

deletes a nucleotide

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18
Q

transformation (def.)

A

uptake of free DNA

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19
Q

transduction (def.)

A

viral-mediated transfer of DNA

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20
Q

conjugation (def.)

A

direct cell-to-cell transfer of DNA (plasmids or part of genome), mediated by sex pilus

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21
Q

Examples of changes in bacterial fitness/reproductive capacity

A
  • resistance to a new antibiotic
  • decreased translation
  • ability to grow at higher temperatures
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22
Q

changes increase bacterial fitness + selection pressure to do so = ______

A

new bacteria will outcompete parent strain

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23
Q

changes increase/don’t change bacterial fitness + selection pressure to do so = _______

A

loss of plasmid & loss of population as fitter organisms outcompete for nutrients

24
Q

Bacteria can grow as ______ (3)

A

-freefloating
-sessile (attached to solid biotic and abiotic surfaces)
-biofilms

25
Q

Sessile bacteria is important for ______

A

protection from predation and physiochemical disturbances & environmental manipulation

26
Q

biofilms (descr.)

A
  • self-produced adhesive matrix primarily of polysaccharide, proteins, and nucleic acid
  • ubiquitous in nature
27
Q

Biofilm development

A
  1. Attachment: add few motile cells to solid surface
  2. Colonization: Polysaccharide formation + growth
  3. Development: more growth and polysaccharide (mature biofilm, has water channels in biofilm)
  4. Active Dispersal: bacteria starts to disperse, triggered by factors like nutrient availability
28
Q

Forces in ECM from polysaccharide that create adhesion

A

-HB
-ionic
-electrostatic
-van der waals

29
Q

Extracellular polymeric substances crucial for biofilm formation; dependent on strain

A
  • Alginate
  • Poly-N-acetylglucosamine
  • Sucrose-derived glucans and fructans
  • Xanthan
  • Cellulose
  • Pel
30
Q

Biofilm growth triggers cells to become ______

A

-more competent and take up DNA

31
Q

Explosive death of Pseudomonas aeruginosa

A
  • Pseudomonas aeruginosa – opportunistic pathogen
  • occurs in a very small proportion of cells when they are under stress (e.g. antibiotics)
  • cells lyse, releasing their DNA (DNA is integrated into EPS)
  • cell membranes form vesicles that protect cells and provide nutrients
32
Q

Biofilm: Streptococcus mutans

A

-lactic acid bacteria found in the oral microbiome
-produces acid from dietary glucose, leading to tooth decay (cavities)
-produces dextran (large neutral polysaccharide that are strongly adhesive); adheres to teeth
-dextran production depends on dietery sucrose

33
Q

_____ is the starting point for dental plaque. Dental plaque biofilm (descr.)

A

-S. mutans
- Many microbes, Heterogeneous, Protective

34
Q

Biofilm has slight ___ charge

A

negative

35
Q

Biofilm function (3)

A

-microbial self-defense (resist physical forces, protection from predators)
-favorable niche (hydration, nutrients, traps extracellular enzymes)
-live in close association for exchange of genetic info, provide nutrients, facilitate communication

36
Q

Biofilm regulation by cyclic diGMP

A

-2 GTP molecules are converted to cyclic diGMP by proteins with GGDEF domains
-cyclic diGMP affects TF, protein modification -> increase biofilm creation, inhibits motility and virulence

37
Q

organisms in biofilms often don’t express ____

A

virulence factors

38
Q

How do bacteria know when to make a biofilm

A

Quorum sensing (bacteria communication)

39
Q

Quorum sensing (def.)

A

is a system of stimulus and response correlated to population density

40
Q

Quorum sensing causes _______. Cell-to-cell communication mediated by small signaling molecules such as _______

A

-coordinated changes in the phenotype of cells in a population
-N-acyl-homoserine lactone (AHL)

41
Q

Quorum sensing couples _________ to transcription regulation

A

cells density and intercellular communication

42
Q

AHL (def.)

A

autoinducer (induces expression of the enzyme that makes it; increase its own production)

43
Q

AHL also induces expression of other genes involved in ______ (4)

A
  • motility
  • sporulation
  • biofilm formation
  • many others
44
Q

Low cell density = ____ conc of AHL + effect on target genes

A

-low
-no transcription of target genes

45
Q

high cell density = ____ conc of AHL + effect on target genes

A

high
-transcription of target genes

46
Q

Light sensing bacteria + quorum sensing

A

Aliivibrio fischeri makes light when cell density is high

47
Q

Quorum sensing causes many unicellular organism to ____

A

behave almost as one organism

48
Q

Not all bacteria produce ______. Quorum sensing molecules can be _______ → lots of variety. Some can detect molecules produces by others - a way of knowing _______

A

-quorum sensing molecules
-small molecules like AHL or can be peptides
-what other organisms are in the environment

49
Q

Escherichia coli and Salmonella enterica do not produce ____ but can detect it –> causes changes in gene expression

A

-AHL

50
Q

Pseudomonas aeruginosa + Quorum sensing

A
  • grows with harming host until threshold conc (high enough AHL to stimulate c-di-GMP production)
    -form biofilm, which protects it from host immune defenses
    -cause disease
51
Q

Vibrio cholerae + Quorum sensing: the signal to make c-di-GMP (and therefore biofilms) is ______

A

-low cell density (e.g. in bodies of water)

52
Q

Vibrio cholerae + Quorum sensing: _____ make EPS (biofilm); their expression is induced by _____

A

-RbmA, Bap1, RbmC
-VpsT and VpsR

53
Q

Vibrio cholerae + Quorum sensing: ___ prevents VpsT and VpsR from promoting _____ transcription

A

-HapR
-RbmA, Bap1, RbmC

54
Q

Vibrio cholerae: biofilm at low cell density

A

At low cell density, sRNA inhibits HapR expression → biofilm

55
Q

Vibrio cholerae: biofilm at high cell density

A

At high cell density, quorum sensing molecules prevent sRNA production → HapR → no biofilm

MICRB 265 (12 decks)

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