Lecture4 Flashcards
(17 cards)
What is central dogma?
What must be accomplished to multiply?
DNA to RNA to protein
DNA replication and dna expression (transcribe and translation)
What is transcription?
What does coupled transcription/ translation in bacteria?
What tells the ribosome to start translation?
Can there be multiple ribosomes and RNA polymerase?
DNA—-> RNA
RNA pol complex starts at promoter ( before gene) ends at transcription terminatior
DNA and RNA and mRNA are all in same place (cytoplasm), so translation begins as mRNA molecule is still being synthesized
**AUG tells ribosome to start translation, binds a little before start codon **
There can be multiple RNA polymerase and ribosomes
but in eukaryotes it occurs at separate time & compartments*
What happens when we don’t need some of the proteins?
How does ecoli do this ?
Regulation of mRNA synthesis, saves energy
When host eats—-> E. coli shuts down pathways to mooch off of host
Nutrients depleted—> ecoli turns on biosynthesis pathways
What are the two parts of regulatory systems??
How?
Sensory kinase:
Membrane spanning
Modifies itself thru autophorylation in response to change
Transfers phosphate group to response regulator
Response regulator:
DNA binding protein—> becomesphosphorylated & changes to bind to DNA to turn transcription on
Via signal transduction
What are DNA binding protein: activator?
Are allosteric—> molecules bind to change conformation and ability to bind to DNA
Facilitates transcription—> positive
Activator binding site is upstream of promoter (before)
Biding of activator enhances RNA polymerases to start transcription
Phosphorylation of (inducer) activator, results in change to allow to bind to DNA
DNA biding proteins: what are repressors?
Allosteric: bind to DNA to turn off transcription, changes conformation
Blocks transcription—> negative regulation
Binds to operator downstream (after) promoter, stops RNA polymerases
Inducer binds to repressor—change—repressor cant bind—> transcription induced
What are 2 ways inducers work?
Bind to activators—> promoting binding to DNA—> RNA polymerases binds
Bind to repressors—> preventing them to bind to DNA, so RNA polymerases binds can
Co regulating bacterial genes:
What info can mRNA carry?
What is Polycistronic message called?
Monocistronic (one) message or
Polycistronic (two genes ) (usually this in bacteria)
Operon
** encoded proteins have related functions**
Explain how bacteria sense the density of cells in their own population.
Via quorum sensing—> act like multicellular organisms, perform tasks together
-can turn off and on gene expression toggehr
-secrete autoinducer to communicate and see who answers
Secrete signaling molecule (autoinducer) —->the concentration of the autoinducer reflects the density of the population
Ex: virulence factors, light production
What are autoinducer (AHL ) in gram negative?
And (AIP) in gram positive?
-AHL (N acyl homoserine lactone) differs between species—- allows for inter species communication,
-AHL can come out and inside of cell easily & bind to activator
—allows for bacteria to distinguish itself
AIP (autoinducer inducing peptides) are peptides— need to be actively transported, via phosphorylation to get into cell
Sensor senses when conc of AIP is high enough—> lets into cell—->so is phosphorylated and bind to response regulator
When does quorum sensing behavior happens and when is it productive? Hence why would it be beneficial for bacterial cells to wait until population density is present?
High cell population density
Productive if action of group of bacteria and unproductive if conducted by individual bacterium
What is biofilm?
What does the extracellular polymeric substance consist of?
Why is it a problem?
How is it beneficial to bacteria?
Group of bacteria that forms a multicellular community
Forms on any surface
Encased in extracellular matrix
Exopolysaccharides, proteins and DNA
Tooth decay, infections, chronic infections
Shelter, protect bacteria from predators and phagocytes, increased tolerance to disinfectants
How does formation of biofilm happen?
Flagella adheres to suface
Multiply and produces EPS (extra cellular polymeric substance) —- quorum sensing
Other bacteria can attach
Cells communicate and create channels in EPS to allow nutritnts and products to pass
Some detach and move to other surfaces to create more biofilms
Interactions between bacteria on biofilms are?
Competive—> some make toxins to kill others
Cooperative
Can foster growth of species that wouldn’t survive otherwise — anaerobs can grow in mouth if other bacteria consume O2
What is horizontal gene transfer?
Benefits?
Acquire brew genes from others
Move genetic material
New genes—> new traits ( pathogenic or antibiotic resistant), quick adapt to new environment
How does conjugation work?
What brings the two cells together?
What promotes it?
Mating—> transfers genetic material thru cell/cell contact
F plasmids in E. coli—> F+ or F -
F pills brings cells close
Enzyme cuts plasmid
Single strand transferred
Complementary strands synthesized in both cells
F+ in both
—plasmids most common
- biofilms promote conjugation
What are three ways of horizontal gene transfer?
Conjugation — main mechanism of HGT
Transformation—> has protein that picks up extra DNA from environments
Transduction—> thru phage
