Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
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?
|
Competence
|
|
|
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?
|
dsDNA
|
|
|
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?
|
-Plasmids
-Transposons -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 -Filamentous |
|
|
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?
|
Induction
|
|
|
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?
|
-Plasmids
-Transposons -Genomic DNA |
|
|
What type of DNA strand is transferred by phage transduction?
|
dsDNA
|
|
|
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
-CTXphage |
|
|
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
-Morphogenesis -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
-Sunlight |
|
|
Does induction of the CTX phage result in vibrio lysis or multiplication?
|
no
|
