Bacterial Genetics & Molecular Biology Flashcards
How does bacteria become drug resistant?
mutation and genetic exchange
What are 3 major molecular targets for antimicrobials?
bacterial replication, gene expression, and cell wall
What did James Watson and Frances Crick do?
worked on the structure of DNA with a double helix
T/F: Watson and Crick were the only ones who were working on the structure of DNA
False! Wilkins, Stokes, Wilson, Franklin, and Gosling also worked on it
Who came up with the central dogma of DNA?
Crick
What is the idea of the central dogma?
DNA–> RNA via transcription
RNA–> protein via translation
What is replication?
DNA synthesis by DNA dependent DNA polymerase
What is transcription?
mRNA synthesis by RNA polymerases on a DNA template
What is translation?
protein synthesis by ribosomes with tRNA and associated factors
How do complexity of DNA correlate with transposons?
more complex= more transposons
so humans have more
What is bacterial DNA present on?
circular chromosome, transposons, and plasmids
How does bacteria replicate?
starts as single circular chromosome and then 2 replication forks going in opposite directions, separating via binary fission to end up with 2 circular daughter DNA molecules
T/F: DNA can only polymerize in 5–> 3 direction on the template
True
There is a forward (leading strand) and backward direction (lagging strand) in a 5—-> 3 direction via DNA polymerase
T/F: bacteria can have only one plasmid
False!
They can have one or more
What can plasmids carry?
protein coding regions with colonization factors, virulence determinants, antibiotic resistance, conjugation pill, and metabolic pathways
What is an R plasmid?
resistance plasmid
What is Campbell Recombination?
plasmids sharing a region (>400bp) readily join together by cross-over homologous recombination
What is a recombinase?
an enzyme that recognizes motifs and can move to plasmid or back and possibly even inactivating an existing gene
- in temperate phages to cause specialized transduction
What encodes the recombinase enzyme?
Transposons
How do transposons allow for movement between cells?
Some transposons contain genes coding for bacterial surface pilli allowing them to move between cells called conjugative transposon
- integrate into chromosome or plasmid
What is a gene?
changes in DNA that lead to heritable phenotypes
What’s a promoter?
sequence in DNA that binds RNA polymerase
T/F: eukaryotic RNA can encode more than 1 protein
False!
Only prokaryotic RNA
What are important targets for specific antibiotics?
bacterial and eukaroytic ribosomes
What are the 3 ways bacteria can exchange DNA?
transformation, transduction, conjugation
What is transformation?
cells take up naked DNA by lysis
- no cell-cell contact required
(only ~1% species but some pathogens)
What is transduction?
phages carry host DNA
(most bacteria)
What is conjugation?
cells mate through specialized appendages (pili/fimbriae)
- usually between same species
ex: F plasmids
- F+ has plasmid already, F- doesn’t have the plasmid
- can integrate similarly to a phage
What is a bacteriophage?
virus that attacks bacteria and replicates it by invading a living cell using the cell’s molecular machinery
What are the 2 types of phages?
- virulent/lytic phages (RNA and DNA)
- infection of susceptible bacteria leads to destruction of bacteria and release of the new infectious phage - temperate/lysogenic phages (DNA) integrates inside
- depend on growth conditions and phages can either lyse host or integrate into chromosome. can go lytic if conditions change
What is Cornyebacterium Diphtheria?
- encoded by a lysogenic phage
- irregular/club shaped gram + rods
- cause diphtheria (stuff in throat) and 20% fatal in children
- vaccine: DTAP
What are the 4 ways bacteria have drug resistance?
- enzymatic medication or degradation of antibiotic (ex: B-lactamase—> why clavulanic acid is added with B-lactams called augmentin)
- alter the target of antibiotic
- change flux of antibiotic
- intrinsic resistance
T/F: Replication, transcription, and translation are important targets for antibiotics.
True!
When will bacteria will have genetic capacity such as active flagella, pili, or enzymes for capsules?
depends on what environment they are in!
What are transposons?
viral-like pieces of DNA that encode an enzyme to allow them excise and integrate elsewhere in the chromosome
- mobile genetic elements
- always encode recombinases
- more transposons, more complex
What do plasmids do for bacteria?
give the bacteria extra capacity to make stuff… worrisome because can allow for production of toxins
What does RNA polymerase recognize?
a degenerate motif in the DNA
How does erythromycin work?
inhibits protein synthesis by binding to ribosome and stopping translation
Which bacteria is shown to have more drug resistance and is an area of interest currently?
gram -
(remember gram + have the thick peptidoglycan wall so this is a big target for many antibiotics)
