Module 13 Flashcards
T/F Only filamentous phage can do a chronic life cycle.
True
When viruses go through the lytic cycle, they are categorized as
virulent phages because this cycle results in the death of a bacterial cell
Describe the difference between lytic cycle, lysogenic cycle, and te chronic cycle.
The lytic cycle refers to viruses that lyse cells so that newly made viruses can exit and infect other cells.
The lysogenic cycle refers to viruses that do not lyse cells but are rather passed down to other cells during cell division.
The chronic cycle refers to viruses that bud off the cell without lysing it.
T/F All tailed phages use the chronic cycle as some point of their infectious cycle.
False. they do not use this due to their tail structure which requires to be assembled inside the cell
Describe the tail contraction method of entry used by many T4 phages.
The phages use their tail fibers to bind to the lipopolysaccharide of gram negative bacteria, which is their cellular receptor. This binding induces a conformational change that results in the formation of pores in both the inner and outer membrane. After the pores are formed, there is a second conformational change that releases a plug protein to form a stabilize channel through which the phage releases its viral DNA.
Some bacteriophage code proteins that can poke holes in the membrane. These proteins are called?
endolysins, holins, and spanins
How does the CRISPR/Cas system works?
After a virus injects its genome into a cell, the genome is degraded. Some of these pieces are then inserted into the CRISPR locus of the bacterial genome and become part of the CRISPR RNA. This CRISPR RNA then guides molecular machinery to target and destroy viral genome.
What does CRISPR stands for ?
Clustered Regularly
Interspaced Short Palindromic Repeats
Why are phages being heavily investigated to treat bacteria infections and such?
It’s believed that bacteria develop very little resistance against phages since phages kill bacterial cells. There are no evidence of cross resistance between different type of phages and antibiotics. Phages also have a low toxicity. Phages also have a low host range and for this reason, they don’t seem to cause disruptions in the human microbiome.
What are the disadvantages of using phages instead of antibiotics?
Phages have very narrow host range, which is disadvantageous if the targeted bacteria mutates. Phages are also living entities, and are therefore not completely predictable.
T/F It’s hard to measure bacteria in our microbiome because only about 1% of bacteria are culturable.
True
What is the difference between targeted metagenomics and shotgun metagenomics.
For targeted metagenomics, first, a sample of bacteria is collected. Second, the DNA of the sample is isolated. Third, PCR is used to amplify the 16S rRNA gene. Lastly, these genes are sequenced and compared to databases of bacterial genomes to identify which bacteria are present.
