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