Week 10 Flashcards by Tami Ojewole

2 ways of bacterial adaptation

-mutations
-acquisition of new DNA

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Two types of mutations

-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 methods of DNA acquisition

-transformation
-transduction
-conjugation

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wildtype strain (def.)

strain isolated from nature

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mutant (def.)

strain with a change in its nucleotide sequence

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genotype (def.)

the nucleotide sequence of an organism

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phenotype (def.)

observable properties of an organism

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point mutation (def.)

single nucleotide change

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missense mutation (def.)

changes the amino acid

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nonsense mutation (def.)

introduces a stop codon

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silent mutation (def.)

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

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cytosine (common form) base pairs with _____

guanine

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

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

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UV radiation causes which type of DNA damage?

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

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frameshift mutation (def.)

-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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insertion (def.)

introduces a nucletoide

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deletion (def.)

deletes a nucleotide

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transformation (def.)

uptake of free DNA

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transduction (def.)

viral-mediated transfer of DNA

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conjugation (def.)

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

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Examples of changes in bacterial fitness/reproductive capacity

resistance to a new antibiotic
decreased translation
ability to grow at higher temperatures

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

new bacteria will outcompete parent strain

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

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

Bacteria can grow as ______ (3)

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

Sessile bacteria is important for ______

protection from predation and physiochemical disturbances & environmental manipulation

biofilms (descr.)

* self-produced adhesive matrix primarily of polysaccharide, proteins, and nucleic acid * ubiquitous in nature

Biofilm development

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

Forces in ECM from polysaccharide that create adhesion

-HB -ionic -electrostatic -van der waals

Extracellular polymeric substances crucial for biofilm formation; dependent on strain

* Alginate * Poly-N-acetylglucosamine * Sucrose-derived glucans and fructans * Xanthan * Cellulose * Pel

Biofilm growth triggers cells to become ______

-more competent and take up DNA

Explosive death of Pseudomonas aeruginosa

* 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

Biofilm: Streptococcus mutans

-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

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

-S. mutans - Many microbes, Heterogeneous, Protective

Biofilm has slight ___ charge

negative

Biofilm function (3)

-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

Biofilm regulation by cyclic diGMP

-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

organisms in biofilms often don't express ____

virulence factors

How do bacteria know when to make a biofilm

Quorum sensing (bacteria communication)

Quorum sensing (def.)

is a system of stimulus and response correlated to population density

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

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

Quorum sensing couples _________ to transcription regulation

cells density and intercellular communication

AHL (def.)

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

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

* motility * sporulation * biofilm formation * many others

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

-low -no transcription of target genes

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

high -transcription of target genes

Light sensing bacteria + quorum sensing

Aliivibrio fischeri makes light when cell density is high

Quorum sensing causes many unicellular organism to ____

behave almost as one organism

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

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

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

-AHL

Pseudomonas aeruginosa + Quorum sensing

- 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

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

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

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

-RbmA, Bap1, RbmC -VpsT and VpsR

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

-HapR -RbmA, Bap1, RbmC

Vibrio cholerae: biofilm at low cell density

At low cell density, sRNA inhibits HapR expression → biofilm

Vibrio cholerae: biofilm at high cell density

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