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41 Cards in this Set

  • Front
  • Back
What is "Natural Transformation"?
Uptake of naked DNA from the environment
In what organisms does natural transformation occur?
Both gram pos and gram neg bacteria
What is required for natural transformation?
What is competence?
An altered physiological state of the microbe, mediated by environmental factors like chemicals and signals.
Where does DNA come from for natural transformation?
It is released from bacterial lysis
In what form is DNA released by bacterial lysis?
What happens when bacterial surface receptors bind to dsDNA for transformation?
It is processed to ssDNA and then internalized.
What are the 2 options for what can happen to transformed linear DNA after internalization?
1. Exonucleases can simply degrade it
2. Homologous recombination to integrate it into the genome
What type of DNA will NOT be degraded by exonucleases? Why?
Plasmids - because they contain their own replicative machinery and exonucleases can't act on circular DNA even if it is single stranded.
What is Conjugation?
Unidirectional passing of DNA via physical contact between bacterial cells
In what microbes can conjugation occur?
Both gram pos and gram neg
What is required for conjugation?
A complex set of genes that encode the pilus
What types of DNA can be transferred through mating bridges in conjugation?
-Chromosomal DNA (pathogenicity islands)
How do gram negatives conjugate?
By forming a pilus mating bridge
How do gram positives conjugate?
The RECIPIENT secretes a pheremone that promotes aggregation on the donor so they come in close contact.
What is oriT?
The origin of Transfer in the donor DNA
What is the process of ssDNA transfer in conjugation called?
Rolling circle replication
What are Bacteriophages?
Obligate intracellular parasites
What are the 3 main types of Bacteriophages?
-Icosahedral heads w/o tails
-Icosahedral heads with tails
What do bacteriophages consist of structurally?
Nucleic acid protected by a protein coat
What is the protein coat of bacteriophages called?
The capsid
What are the 3 variations of lifecyles that bacteriophages can live?
1. Lytic
2. Lysogenic
3. Temperate - both
What occurs in the lytic lifecycle?
The phage injects is genetic material into a microbe, and once it is copied and new phage has been built, the microbe is lysed.
What occurs in the lysogenic lifecycle?
The phage DNA is held in a repressed state that is capable of being activated by environmental factors.
What is it called when the prophage within a lysogen is activated?
How big are the bacterial DNA fragments posessed by bacteriophages?
The same size as viral DNA
What types of bacterial DNA are bacteriophages capable of transferring?
-Genomic DNA
What type of DNA strand is transferred by phage transduction?
What limits the range of hosts that can receive phage genes?
The cell receptors on the host cells
What type of phage carries the DNA that encodes cholera toxin?
What is the name of this phage?
A filamentous bacteriophage
How big is the cholera toxin phage genome? What is its structure like?
~7000 nt's
-Made of a core element + repetitive sequences
What are the cholera toxins?
ctxA and ctxB
What are Ace and Zot?
Genes that encode
-Enterotoxic activity
What is the lifecycle of the CTX phage?
Temperate - maintained in genome within a lysogen, or as extra chromosomal RF
What type of phase results in more diarrhea associated disease symptoms?
Genome-associated CTX
What bacterium gets infected by the CTX phage?
Vibrio cholera
How does the CTX phage bind and infect vibrio cholera?
Via toxin co-regulated pilus (TCP)
Where is tcp encoded?
On a pathogenicity island within vibrio's genome.
What is the environment in which CTX phage is most efficiently transferred?
In the GI tract
What are 2 other environmental factors that cause induction of phage transfer?
-UV light
Does induction of the CTX phage result in vibrio lysis or multiplication?