Microbiology Final Exam
cholera process
1) attaches to intestinal epithelium(B subunit allows attachment), toxin is secreted. 2) A unit enters cell 3) gated ion channels open (signal transduction pathway) 4)electrolytes leave from open channels 5) water follows electrolytes out of cell by osmosis into the lumen
Describe the process of generalized transduction
1. Lytic phage infects a target cell and causes DNA to fragment 2. lytic phage incorporates bacterial chromosomal DNA into its phage head 3. this phage can infect another bacteria 4. the DNA it carried can be incorporated into the host chromosome via homologous recombination (Occurs because of error in packaging)
Coagulase
A bacterial enzyme that causes blood plasma to clot Causes hair follicle infections, its mechanism is adhesion
Lysogen
A bacterium that carries phage DNA (a prophage) integrated into its genome
Which components would you find in all viruses?
A capsid and proteins
lysogenic cycle
A phage replication cycle in which the viral genome becomes incorporated into the bacterial host chromosome as a prophage and does not kill the host.
Temperate phage
A phage that is capable of reproducing by either the lytic or lysogenic cycle. Makes lysogen immune to superbugs (infection by the same phage)
Endotoxin
A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die. Causes staph food poisoning
Would you expect a transducing phage to reproduce in a host? Why or why not?
A transducing phage would not reproduce in a host because the virus is injecting bacterial DNA into the cell, not viral DNA. Bacterial DNA does not have the genetic information that encodes for viral replication so it would not happen. Instead, the bacterial cell uses homologous recombination to insert the DNA into its genome. The daughter cells will have this new DNA, and will not produce viruses.
What is a viral receptor and why is this a poor term?
A viral receptor is a protein receptor on the cell's membrane that the viral proteins can bind to and then allow it to enter the cell. It is a poor term because it makes it seem as though the receptor is there specifically for the virus. However, the membrane receptors can be channels, pores, pumps, or ligand binding proteins.
Enveloped virus
A virus enclosed within a phospholipid membrane derived from its host cell.
Viral spikes
Attach specifically to host cell receptors
Animal virus replication (enveloped virus)
Attachment: spikes of a vision attach to specific host cell receptors Membrane Fusion: envelope of vision fuses with cytoplasm Nucleocapsid release: nucleocapsid is released into the cytoplasm, viral envelope remains part of the cytoplasmic membrane Uncoating: nucleic acid separates from capsid Synthesis: nucleic acids and proteins
How does generalized transduction differ from the lytic cycle?
Differs because as the viruses are coming together, some will envelope broken pieces of cellular DNA that will be incorporated into the capsid which creates a transdusing particle
restriction enzymes
Enzyme that cuts DNA at a specific sequence of nucleotides
Synthesis
Expressin of viral genes to produce viral structural and catalytic genes like capsid proteins and enzymes required for replication
Viral matrix proteins
Give the virus its shape, only present in enveloped viruses
How is generalized transduction similar to a normal lytic replication cycle?
It begins the same with a virus inserting its DNA into a host cell, destroying the host cell's genome, and then creating more viruses.
To be considered a virus, a virus must..
Only replicate inside of a host's cytoplasm
Capsid
Outer protein coat of a virus
What is specialized transduction?
Part of the bacterial DNA adjacent to the incorporated viral DNA becomes part of the virus that will take it to another bacterial cell. It's called specialized because it's always typically the same part of the DNA. Some of the viral DNA is also left within the host cell's genome. This makes every phage produced inside this cell ineffective, and no other phages will be produced by these phages when they infect a host cell.
Lytic phage
Phage attaches to specific receptors on the cell wall, tail contracts and phage DNA is injected into the bacterial cell leaving the phage coat outside. Phage genome is transcribed and phage proteins are synthesized. Phage DNA is replicated and host DNA is destroyed. Phage components are assembled and then the cell lyses and phages are released
If you are analyzing the DNA sequence of a non-pathogenic E. coli bacterium and notice that it has a gene that is most similar to another pathogenic strain of E. coli. Upon further analysis, there are no other flanking genetic sequences that have been transferred... just the gene. Which of the following modes of HGT could explain this result? Explain your reasoning.
Specialized transduction Generalized Transduction Transformation Conjugation between HFR and F- For specialized and conjugation, it could happen if only the bacterial chromosomal DNA was incorporated and not the viral genes or the F plasmid genes
Which stage of the viral replication cycle (attachment, uncoating, entry, synthesis) best explains why bacteriophage do not infect human cells?
The attachment phase best describes why the bacteriophage can only infect bacteria. Viruses can only infect cells that have very specific proteins on their membrane. If the cell doesn't have the proteins that the virus can bind to then the virus will not bind to the cell. Human cells do not have the same membrane proteins as bacteria do, which explains why bacteriophages can't infect human cells.
Which type of bacteriophage is most similar to a chicken pox virus: T4 or lambda? Explain your reasoning in terms of their respective life cycles.
The chicken pox virus has a latent phase within the human body where it does not show any symptoms. This means that it is most similar to the lambda life cycle since lambda will have a latent phase, while T4 will go immediately to the lysing phase of the cell.
Which component of an enveloped virus is directly involved with attachment to a host cell?
The envelope
Bacteriophage vs eukaryotic phage
The genome, but not the protein coat, enters the cell
Exfoliation
The removal of excess dead cells from the skin surface. Causes Staph scalded skin syndrome
Prophage
The viral DNA that is embedded in the host cell's DNA
Exit of enveloped viruses
They exit through budding and that is how they get their envelope. In this way the cell can still be alive after the virus has left it
Exit of bacteriophages
They lyse the cell and kill it in order to exit the cell.
Suppose a bacteriophage infected a mutant E. coli cell that is unable to perform homologous recombination
Transducing phage has some of the bacterial DNA that is mistakenly encapsulated. So yes it could form for generalized. No for specialized because specialized has to do with homologous recombination
Which of the following mechanisms is most likely the explanation of how N. gonorrhoeae acquired human DNA? A. Transformation B. Conjugation C. Transduction
Transformation: this is because conjugation can only occur between two bacterial cells, not between a eukaryotic cell and a bacterial cell. Transduction is not an option because viruses can't infect both a eukaryotic cell and a bacterial cell. They are too specific to infect both types of cells so it would be impossible to have gene transfer this way. The most likely is transformation because gonorrhoeae kills human cells they likely picked up naked human DNA from the environment
Lysogenic infection
Type of infection in which a virus embeds its DNA into the DNA of the host cell and is replicated along with the host cell's DNA. It is silent and does not produce any affects while this is occurring. Can return to a phage and continue the lytic cycle. This will occur when the cell has damage to its DNA
Lysogenic conversion
When a bacterium acquires a new trait from its temperate phage
CRISPR
a collection of DNA sequences that tells Cas9 exactly where to cut
Specialized transduction
a highly specific part of the host genome is regularly incorporated into the virus results from error in DNA exiting chromosome, both bacterial and phage chromosome presents
cytotoxin
a substance having a specific toxic effect on certain cells
neuraminidase antigen
aids in release of newly formed virions
Pili virulence factor
allow for adhesion
differential media
allows growth of several types of microbes and displays visible differences among those microbes
Lysozyme
an enzyme found in saliva and sweat and tears that destroys the cell walls of certain bacteria
Replicase
an enzyme that catalyzes the synthesis of a complementary RNA molecule using an RNA template. (very sloppy RNA polymerase makes many errors and introduces alot of mutations)
clumping factor
attaches to clots and tissue, aids colonization Causes hair follicle infections, its mechanism is adhesion
Hemagglutinin antigen (HA)
attaches to specific receptors on ciliated epithelial cells and allows viral entry
How does Tamiflu work?
by preventing the activity of the neuraminidase antigen (NA) that helps a new virus detach from the infected cell
Superantigens
cause an intense immune response due to release of cytokines from host cells
Hyaluronidase
digests polysaccharides that hold cells together Causes wound infections
Which viral type has a genome that can be directly translated?
ds DNA ss (+) DNA ss (-) DNA ss (+) RNA
Adhesins
enable parasites to attach to host cells or tissues
Lipases
enzymes that break down lipids Causes wound infections
Proteases
enzymes that continue the breakdown of polypeptides in the small intestine Causes wound infections
chemically defined media
exact chemical composition is known
Toxic shock syndrome toxin
induces fever, vomiting, shock, systemic organ damage causes Toxic Shock Syndrome
complex media
nutrient rich but poorly defined
Non-enveloped viruses COULD have
protein spikes Single stranded DNA Single stranded RNA Double stranded DNA
Enveloped viruses COULD have .... (check all that apply)
protein spikes matrix protein Single stranded DNA Single stranded RNA Double stranded DNA A phospholipid bilayer
A virus that has which type of genome must carry replicase within the viral particle?
ss (-) RNA
selective media
suppress growth of unwanted bacteria and encourage growth of desired microbes
Methylation of DNA
the process by which the methyl groups are added to certain nucleotides in genomic DNA making them unrecognizable to endonuclease